Glossary of Terms

-- All definitions -- Ataxia / Olivopontocerebellar atrophy Bradykinesia Choreoathetosis Conditions associated with movement disorders Corticobasal degeneration Dyskinesias, paroxysmal Dystonia Essential tremor - See Tremor Hemiballismus Hemifacial spasm Hereditary Spastic Paraplegia Huntington's disease Multiple system atrophy Myoclonus Parkinson's disease Paroxysmal Dyskinesias Progressive supranuclear palsy Restless legs syndrome Rett syndrome Spasticity Stiff-person syndrome Sydenham's chorea Tardive dyskinesia / Dystonia Tics / Tourette's syndrome Tremor Wilson disease

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Ablation: Surgical destruction or removal of tissue, an organ, or a precise region of a particular structure. Ablation may involve surgical cutting (excision); chemical destruction, such as injection of phenol; or the use of high frequency electrical current or radio waves. For example, pallidotomy is a procedure used in the treatment of Parkinson's disease or certain other movement disorders. The procedure involves surgical ablation of part of the internal portion of the globus pallidus (GPi)--i.e., a brain region involved in regulating movement--in an attempt to "rebalance" movement and posture control. Once a wire probe is inserted into and precisely positioned within the GPi, it heats and destroys adjacent tissue through the emission of radio waves.

Accelerometer: A device used to measure the rate of change in velocity over a specific period of time. Measures the rate or "speed" of the tremor cycle.

Acetylcholine (ACh): Acetylcholine is a type of neurotransmitter. It is a chemical that is used by neurons to communicate with other neurons and with parts of the body. It is also used by the part of the nervous system that is responsible for resting and digesting. It causes the lowers blood pressure and slows down heart rate and breathing rate.

Action tremor: a tremor that occurs during the performance of voluntary movements. Such tremors include postural, isometric, kinetic, and intention tremors.

Activities of daily living (ADL): functions that are typically performed as part of a person's daily routine, such as dressing, bathing, eating, toileting, leisure activities, socialization, and other functions of daily living.

Acute: Referring to symptoms of abrupt onset, often of marked severity or intensity.

Adenosine triphosphate (ATP): ATP is the molecule that provides the energy in the cells of all living things.

Adverse event: According to the United States Food and Drug Administration, an adverse event is any undesirable experience associated with the use of a medical product in a patient. The event is serious and should be reported when the patient outcome is death or is life-threatening; results in hospitalization, disability, or congenital anomaly; or requires intervention to prevent permanent impairment or damage.

Agonist: A muscle whose contraction executes an intended movement.

Akathisia: a neurologic condition of motor restlessness, manifested by a sensation of muscular quivering, an urge to constantly move about, and an inability to sit still.

Akinesia: Akinesia is an absence of movement. It comes from two Greek words—a and kinçsis—a means without, and kinçsis means movement.

Akinetic: Referring to absence or poverty of voluntary movement; loss of the ability to move all or part of the body.

Alpha 2-adrenergic agonist: A drug that reduces the activity of the neurotransmitter norepinephrine by stimulating certain receptors within the central nervous system (central presynaptic alpha 2-adrenergic receptors). The release of norepinephrine triggers action within the sympathetic nervous system. This part of the nervous system regulates certain involuntary activities during stress, such as increasing the heart rate, deepening breathing, and raising blood pressure. Norepinephrine also plays a role in regulating mood and emotion. The administration of alpha 2-adrenergic agonists may result in a reduced heart rate and lowered blood pressure and have depressive or sedative effects.

Alpha synuclein: Alpha synuclein is a protein found in the brain. Nobody knows what the function of the protein is. In some diseases it is found in large quantities clumped together. It is found in Parkinsons Disease, and other diseases like Lewy Body Dementia and Multiple Systems Atrophy.

Alzheimer disease: Alzheimer disease is a disease of the nervous system in which tangles and plaques of proteins develop in the brain, and brain tissue shrinks. The result is impaired abstract thinking and judgment, personality changes, abnormal behavior, and memory problems. Alzheimer disease is one of the leading causes of dementia.

Ambulant (ambulatory): Able to walk; may be used to describe patients who do not require a wheelchair or are not confined to bed.

Ambulation: The act of walking.

Amino acid: The chemical "building blocks" or basic structural units of proteins. All proteins in the body are formed from a "pool" of 20 different amino acids. Some are essential amino acids and must be supplied by the diet. The remainder are classified as "nonessential." These can be made by the body and need not come from the diet.

Amniocentesis: A screening or diagnostic procedure during which a sample of amniotic fluid surrounding the developing fetus is withdrawn by means of an ultrasound-guided needle. The amniotic sac is a fluid-filled membrane that surrounds and protects the developing fetus within the uterus. Amniotic fluid contains cells that may be used for DNA analysis, chromosomal testing, and enzyme studies. Such testing may detect certain genetic disorders, metabolic diseases, chromosomal abnormalities, or developmental defects. This procedure is typically performed between the 14th and 18th week of pregnancy.

Amplitude: the "size" or "height" of a tremor; the extend or breadth of a tremor's range.

Analog (Analogue): (1) A chemical compound or agent that is similar to another in structure yet differs concerning a particular element; it may have a similar or different mode of action. (2) A tissue, organ, or other bodily structure that has the same function or organization as another yet has a different evolutionary origin.

Animal model: An animal model is a laboratory animal that is used in research. Scientists can create an animal with specific characteristics or the animal may naturally have specific characteristics that resemble a human disease or condition.

Anosmia: Anosmia is a lack of sense of smell. People who have complete anosmia are not able to detect any odors. People who have partial anosmia are not able to detect one or more odors.

Antagonist: (1) A drug that blocks a receptor, preventing stimulation. (2) A muscle whose contraction opposes an intended movement.

Antibodies: Specialized proteins that function as an essential part of the immune system. Antibodies are produced by certain white blood cells (B cells) in response to the presence of specific, usually foreign proteins (i.e., antigens), helping the body to neutralize and destroy the invading microorganism, foreign tissue cell, or other antigen in question.

Anticholinergic agents: Anticholinergic medications are drugs that block the action of acetylcholine, a neurotransmitter with an effect opposite to that of dopamine. By blocking the action of acetylcholine, these drugs increase the ability of dopamine to control movement. Examples of anticholinergic drugs used in the treatment of Parkinson disease include trihexyphenidyl (Artane®), benztropine (Cogentin®), and ethopropazine (Parsidol®).

Anticholinesterase: An agent that inhibits action of acetylcholinesterase (AChE). AChE is an enzyme that inactivates acetylcholine, a neurotransmitter at the junctions of nerve and muscle cells (neuromuscular junctions) that regulates the delivery of messages from neurons to muscle fibers. By inhibiting the activity of AChE, such medications allow high levels of acetylcholine to accumulate, potentially enabling repeated stimulation of nerves at neuromuscular junctions.

Anticonvulsant medication: An agent that prevents or arrests convulsive seizures.

Antiemetic: A drug that reduces nausea and vomiting.

Antigen: Any substance that may trigger a particular immune response, such as the production of antibodies. Antigens may be foreign proteins of invading microorganisms (e.g., viruses, bacteria), toxins, or foreign tissue cells (e.g., used in transplantation).

Antihistamine: a drug that counters the effects of histamine, a compound that causes dilatation of capillaries, contraction of smooth muscle, and stimulation of gastric acid secretion and that is released during allergic reactions.

Antioxidants: Agents that inhibit or neutralize potentially harmful compounds known as free radicals. Free radicals are produced during metabolic activity. High levels of free radicals may eventually lead to impaired functioning and destruction of neurons and other bodily cells. Certain antioxidants are thought to neutralize free radicals before cellular damage occurs.

Aorta: The main artery of the body. The aorta receives oxygen-rich (oxygenated) blood from the lower left chamber (ventricle) of the heart for distribution to most arteries of the body, with the exception of the pulmonary artery, which distributes oxygen-deficient (deoxygenated) blood from the lower right ventricle to the lungs.

Apomorphine: Apomorphine is a type of drug that is being studied to treat severe Parkinson’s disease. It is made from morphine but does not actually contain morphine. It increases the levels of dopamine available in the brain.

Apoptosis: Cell death due to a programmed pattern of gene expression; a form of cell death in which certain enzymes activate to degrade DNA within the nucleus, resulting in cellular degeneration and loss.

Apraxia: Loss of the ability to sequence, coordinate, and execute certain purposeful movements and gestures in the absence of motor weakness, paralysis, or sensory impairments. Apraxia is thought to result from damage to the cerebral cortex, such as due to stroke, brain tumors, head injury, or infection. It may also occur as a result of impaired development of the cortex as in certain neurodevelopmental disorders, including Rett syndrome. Apraxia may affect almost any voluntary movements, including those required for proper eye gaze, walking, speaking, or writing.

Archimedes spirals: a relatively simple test used to evaluate tremor severity. During this test, the patient is asked to draw increasingly wider circles on a piece of paper.

Asterixis: involuntary, jerking or flapping movements, especially of the hands. Extending the patient's arm with the wrist bend in a backward position may induce this form of tremor, which may be associated with advanced liver disease.

Astrocyte: A type of glial cell. Glial cells are the connective tissue cells of the central nervous system (CNS), serving as the supportive structure that holds together and protects neurons. Astrocytes are relatively large glial cells with thread-like projections that connect with neurons and small blood vessels (capillaries). These projections form part of the so-called "blood-brain barrier." This barrier slows or prevents the passage of unwanted substances, such as harmful chemicals, infectious agents, etc., from the bloodstream into the brain. Astrocytes also accumulate in areas where nerves have been damaged (astrocytosis), sealing off these areas. An excess of astrocytes in damaged areas of the CNS is known as gliosis.

Ataxia: A condition characterized by an impaired ability to coordinate voluntary movements. Ataxia may result from damage to the cerebellum, cerebellar pathways, or the spinal cord due to various underlying disorders, conditions, or other factors. These may include infection, head injury, stroke, brain tumors, neurodegenerative disorders, alcohol or drug intoxication, or certain hereditary diseases (e.g., Friedreich's ataxia, ataxia-telangiectasia). Associated symptoms may vary, depending upon the site of damage within the central nervous system. However, the condition is often characterized by incoordination, postural imbalance, and a lurching, unsteady manner of walking (gait). Additional findings may include slurred speech (dysarthria); rapid, involuntary, rhythmic eye movements (nystagmus); and/or other abnormalities.

Ataxia-telangiectasia (AT): A hereditary, progressive disorder that typically becomes apparent in early childhood and is characterized by increasing neurodegenerative changes of the cerebellum, a brain region involved in producing coordinated voluntary movements, sustaining balance, and maintaining proper posture. Associated symptoms typically include delayed motor development; an unsteady, awkward manner of walking; drooling; impaired articulation of speech (dysarthria); dependence on thrusts of the head to achieve proper focusing of the eyes; and involuntary, rapid, jerky eye movements (nystagmus). Affected children may also develop involuntary, "shock-like" muscle spasms (myoclonus); sustained muscle contractions that result in repetitive twisting motions or unusual postures or positions (dystonia); or irregular, jerky, relatively rapid involuntary movements (chorea). AT is also typically associated with permanent widening (dilation) of groups of blood vessels (telangiectasias), particularly in sun-exposed skin regions of the face and the transparent membranes covering the whites of the eyes. In addition, AT is characterized by deficient functioning of the immune system (immunodeficiency), leading to recurrent respiratory and skin infections and an increased risk of certain malignancies (e.g., certain leukemias or lymphomas). The disorder, which is transmitted as an autosomal recessive trait, is thought to result from defective repair of DNA.

Athetosis: Involuntary, relatively slow, writhing movements that essentially flow into one another. Athetosis is often associated with chorea, a related condition characterized by involuntary, rapid, irregular, jerky movements. Although athetosis may be most prominent in the face, neck, tongue, and hands, the condition may affect any muscle group. Athetosis may occur in association with certain neurodegenerative diseases, such as Huntington's or Wilson's disease, or cerebral palsy (CP). It may also result from infections affecting the brain or the use of particular medications.

Atrophy: Wasting away or loss of a cell, tissue, or organ due to disease, malnutrition, insufficient blood supply, or other causes, such as loss of skeletal muscle mass due to peripheral nerve damage.

Attention-deficit/hyperactivity disorder: a diagnosis applied to children and adults who consistently display certain characteristic behaviors over a period of time. The most common behaviors fall into three categories: inattention, hyperactivity, and impulsivity.

Atypical: Irregular; not standard or characteristic; not conforming to type.

Atypical neuroleptics: Antipsychotic drugs that cause less parkinsonian side effects than older treatments for psychosis.

Auditory: Pertaining to the sense of hearing or the organs involved in hearing.

Augmentation: A phenomenon that may occur as a result of the use of certain medications (particularly levodopa). Augmentation is characterized by the emergence of worsening symptoms earlier in the day (e.g., early evening, afternoon, or morning). Many people who take levodopa and some who take other dopamingeric agents develop augmentation, especially those who have severe symptoms or are taking high doses of the drug.

Autoimmune: Referring to an immune response against one's own tissues or organs. Autoimmune diseases result from abnormal immune reactions in which the actions of certain white blood cells (T cells) are directed against "self proteins" (autoantigens) or normal tissue components (i.e., cell-mediated immune response)--or in which specialized proteins (antibodies) produced in response to specific, usually foreign proteins (antigens) improperly act against certain of the body's own cells (i.e., antibody-mediated immune response). In certain disorders, the autoimmune process may be primarily directed against one organ, such as the thyroid gland in Hashimoto's thyroiditis or the pancreas in insulin-dependent diabetes mellitus, or may involve multiple organs and bodily systems, such as associated with systemic lupus erythematosus (lupus or SLE).

Automatic behavior: Automatic behaviors are those during which a person performs a routine task without any awareness of doing so.

Autonomic dysregulation: malfunctioning of the autonomic nervous system, the portion of the nervous system that conveys impulses between the blood vessels, heart, and all the organs in the chest, abdomen, and pelvis and the brain (mainly the medulla, pons and hypothalamus).

Autonomic nervous system: The autonomic nervous system controls most of the involuntary reflexive activities of the human body. The system is constantly working to regulate the glands and many of the muscles of the body through the release or uptake of the neurotransmitters acetylcholine and norepinephrine. The autonomic nervous system is made up of two primary parts: the sympathetic and parasympathetic systems. The sympathetic nervous system prepares the body for emergencies or times of stress and is responsible for the body's "fight or flight" response when faced with a dangerous situation. During this response, the heart rate and blood pressure increase, the pupils of the eye dilate, and the digestive system slows down. The parasympathetic system helps the body's functions return to normal after they have been stimulated by the sympathetic nervous system and also has some responsibility for keeping the body's immune system properly functioning.

Autonomic testing: Your autonomic nervous system controls a variety of functions in your body, including blood pressure, heart and breathing rates, and sweating. Autonomic testing is used to see of your autonomic nervous system is working as it should be or if you have had damage to nerves in this system. Testing usually involves measuring your blood pressure, blood flow, heart rate, the amount of sweat you produce, and your skin temperature.

Autosomal dominant: Human traits, including eye color, hair color, and disorders, are passed down from one generation to the next through genes. A person has two genes for each trait—one from the father and one from the mother. In autosomal dominant disorders, it only takes one bad gene to have the disease. The bad gene dominates over the normal gene, which can cause the person to have the disease. If an individual has an autosomal dominant disease, each of his or her children has a 50% chance of having the disease.

Autosomal recessive trait: Human traits, including an individual's hair color, specific blood group, or expression of certain diseases, result from the interaction of one gene inherited from the mother and one from the father. With autosomal recessive disorders, two copies of the disease gene must be inherited in order for an individual to potentially develop the disease. If both the mother and father carry a copy of the disease gene, each child has a 25 percent risk of inheriting the two genes for the disease. There is a 50 percent risk that their children may inherit one copy of the disease gene and be carriers for the disease trait (heterozygous carriers). In addition, there is a 25 percent chance that the parents' offspring will inherit two normal copies of the gene and will not develop the disorder nor be carriers for this disease trait.

Axons: Nerve fibers. Axons are the relatively slender extensions of neurons that transmit nerve impulses away from nerve cell bodies. The ends of the axons or "terminals" release chemical substances known as neurotransmitters, enabling the transmission of nerve impulses to other neurons or effector organs. The whitish, fatty, protein-containing substance called myelin forms an insulating, protective, cylindrical sheath around some axons, serving to increase the speed and efficiency of nerve impulse transmissions.

Baclofen: A mainstay of antispastic drug therapy, baclofen is a GABA agonist that stimulates the GABAB autoreceptor. When stimulated, this autoreceptor inhibits muscle activity. In experimental systems, baclofen inhibits the release of noradrenaline, and acetylcholine from peripheral nerve endings, and acetylcholine, noradrenaline, dopamine, serotonin, and glutamate from CNS neurons.

Ballismus: An abnormal neuromuscular condition that is generally considered a severe form of chorea. Involvement of the upper muscles of the arms and legs results in uncontrolled, violent, flinging or throwing actions. These swinging or jerky movements may be sporadic or continuous and, in some patients, restricted to one side of the body (hemiballismus). Ballismus often occurs in association with other abnormal involuntary movements, including athetosis, chorea, and dystonia.

Basal ganglia: The basal ganglia are structures located deep inside the brain. It is responsible for normal movement, such as walking. It is made up of three parts—the caudate nucleus, putamen, and globus pallidus.

Behavior therapy: Behavior therapy is a method of treating psychiatric disorders that focuses on getting rid of abnormal or maladaptive behavior by reinforcing desired behavior and extinguishing undesired behavior.

Benign myoclonus of infancy: A neurologic condition that typically becomes apparent by approximately 4 months of age. Affected infants and children experience relatively short, mild episodes of myoclonus, or sudden, involuntary, "shock-like" spasms of muscles, particularly of the head, neck, trunk, and arms. Development is typically normal, and myoclonus usually ceases by age 2 or 3.

Benzodiazepines: A class of medications that act upon the central nervous system to reduce communication between certain neurons, lowering the level of activity in the brain. Benzodiazepines are effective in reducing anxiety, stress, or agitation; promoting sleep; alleviating restlessness; and relaxing muscles.

Beta-adrenergic receptor: a specialized molecular structure on the surface membrane of a neuron that selectively receives the neurotransmitter norepinephrine. Reception of this neurotransmitter causes changes in the neuron that increase its likelihood of "firing" or sending its own signal to other neurons. The activities of norepinephrine affect that part of the nervous system involved in the control of some involuntary body functions, such as blood pressure regulation, etc. (sympathetic nervous system).

Bilateral: Having or affecting two sides.

Biosynthesize: To form or produce (during normal physiologic functions) a chemical compound in the body.

Biphasic: having two distinct stages or phases.

Blood-brain barrier: The brain is a very important and delicate organ in the body. The blood-brain barrier protects the brain from being damaged by anything that can get into the blood system. The barrier keeps chemicals and toxins out. Many drugs that people take get into the blood system but cannot reach the brain unless they are specifically designed to do so.

Body mass index: The body mass index is a measure of body fat that is based on a person’s height and weight.

Botulinum toxin (BTX): Any of a group of toxins, designated as A through G, produced by Clostridium botulinum bacteria. Localized injection of minute amounts of commercially prepared BTX may help to relax an overactive muscle by blocking the release of acetylcholine, a neurotransmitter responsible for the activation of muscle contractions.

Bowel: The bowel is the last part of the digestive tract. It is also called the intestines. There is both a large and small bowel. Nutrients and water are absorbed from the small bowel into the body. The left over waste moves through to the large bowel. It is stored here until the waste is emptied from the body by a bowel movement in to form of stool or feces.

Bradykinesia: Bradykinesia simply means abnormally slow movement. It comes from two Greek words—bradys and kinçsis—bradys means slow or slowly, and kinçsis means movement.

Brainstem: The region of the brain consisting of the medulla oblongata, pons, and midbrain. The brainstem primarily contains white matter interspersed with some gray matter. This area of the brain serves as a two-way conduction path, conveying nerve impulses between other brain regions and the spinal cord. In addition, most of the 12 pairs of cranial nerves from the brain arise from the brainstem, regulating breathing, digestion, heartbeat, blood pressure, pupil size, swallowing, and other basic functions.

Branched-chain amino acids: the essential amino acids, isoleucine, leucine, and valine.

Bruxism: Involuntary grinding, clenching, or gnashing of the teeth, particularly during sleep or times of stress. Without appropriate protection, such as the use of night guards that cover the teeth, severe dental problems may result. Bruxism may also be a feature of certain neurologic movement disorders, including dystonia of the jaw, mouth, and lower face (oromandibular dystonia [OMD]), Rett syndrome, or tardive dyskinesia.

Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS): The BFMDRS is a weighted scale that measures the severity and provoking factors for dystonia in 9 body areas, including the eyes, mouth, speech or swallowing, neck, right and left arms, trunk, and right and left legs

Cabergoline: Cabergoline is an ergotamine-based dopamine-receptor agonist with a half-life of 65 hours. In the United States, it is marketed as Dostinex for the treatment of the rare disorder, hyperprolactinaemia, or high levels of the hormone prolactin.

Carbidopa: Carbidopa is a drug that, when combined with levodopa, slows the peripheral breakdown of the levodopa, thereby allowing more of the levodopa to enter the brain.

Carbonic anhydrase inhibitors: A class of medications that inhibits activity of the enzyme carbonic anhydrase. This zinc-containing enzyme is present in red blood cells and the renal tubules. These tubules form part of the filtering units of the kidneys. Carbonic anhydrase activity serves to accelerate the transfer of carbon dioxide from tissue to the blood and on to the lungs. By restricting carbonic anhydrase activity, these agents decrease hydrogen ion concentrations in the renal tubules, increasing excretion of sodium, potassium, bicarbonate, and water. Certain carbonic anhydrase inhibitors are prescribed to promote urinary production and excretion (i.e., as diuretics) or to lower fluid pressure within the eyes for those with glaucoma. They are also used to treat other conditions including epilepsy or certain neurologic movement disorders.

Carnitine: A natural substance found in skeletal and cardiac muscle and the liver. Carnitine serves to transport fatty acids across mitochondrial membranes, thereby playing an important role in energy production and the metabolism of fatty acids.

Cataplexy: Cataplexy is a sudden loss of voluntary muscle control, usually triggered by emotions such as laughter, surprise, fear or anger. Cataplexy occurs most often during times of stress or tiredness. The loss of muscle control may vary from a feeling of weakness to total body collapse. Although people having a cataplectic attack may appear to be asleep, they are actually awake, just unable to move.

Catecholamine: any of a group of hormones that are catechol derivatives, e.g., adrenaline and noradrenaline.

Caudate: One of the three major substructures that, together with the globus pallidus and putamen, form the basal ganglia. The caudate nuclei and putamen, which are relatively similar structurally and functionally, are collectively known as the striatum. Specialized clusters of nerve cells or nuclei within the caudate receive input from certain regions of the cerebral cortex. This information is processed and then relayed (by way of the thalamus) to areas of the brain responsible for controlling complex motor functions. The caudate nuclei are specifically thought to process and transmit cognitive information that influences the initiation of complex motor activities.

Caudate nuclei: One of the 3 major substructures that, together with the globus pallidus and putamen, form the basal ganglia. The caudate nuclei and putamen, which are relatively similar structurally and functionally, are collectively known as the striatum. Specialized clusters of nerve cells or nuclei within the caudate receive input from certain regions of the cerebral cortex. This information is processed and then relayed (by way of the thalamus) to areas of the brain responsible for controlling complex motor functions. The caudate nuclei are specifically thought to process and transmit cognitive information that influences the initiation of complex motor activities.

Central nervous system (CNS): The central nervous system (CNS) is made up of the brain and spinal cord. It coordinates and controls the entire body. It does this by sending signals to the body to move and receives signals from the body about the surrounding environment.

Central oscillators: nerve cells that discharge signals that result in alternating fluctuations of electrical impulses along certain tracts of the central nervous system.

Cerebellum: A two-lobed region of the brain located behind the brainstem. The cerebellum receives messages concerning balance, posture, muscle tone, and muscle contraction or extension. Working in coordination with the basal ganglia and thalamus, the cerebellum integrates, adjusts, and refines messages transmitted to muscle groups from the cerebral cortex (i.e., motor cortex). Thus, the cerebellum plays an essential role in producing smooth, coordinated voluntary movements; maintaining proper posture; and sustaining balance.

Cerebral cortex: The outer region of the brain's cerebral hemispheres. Comprised of gray matter, the cerebral cortex contains several deep folds (gyri) and grooves (sulci or fissures). Two sulci divide the surfaces of both cerebral hemispheres into four distinct lobes that are named for overlying bones of the skull. These include the frontal, temporal, occipital, and parietal lobes. The cerebral hemispheres are joined by a thick band of nerve fibers known as the corpus callosum. The cerebral cortex is responsible for integrating higher mental functioning and conscious thought, sensations, and general movements.

Cerebrospinal fluid (CSF): The fluid that flows through and protects the 4 cavities (ventricles) of the brain, the spinal cord's central canal, and the space (known as the subarachnoid space) between the middle and inner layers of the membrane (meninges) enclosing the brain and spinal cord. Laboratory analysis of CSF, usually obtained via lumbar puncture, may help to diagnose central nervous system infections, certain tumors, or particular neurologic disorders. During lumbar puncture, CSF is removed from the spinal canal via a hollow needle inserted between certain bones of the spinal column within the lower back (i.e., usually the third and fourth lumbar vertebrae).

Chemodenervation: Interruption of a nerve impulse pathway via administration of a chemical substance, such as botulinum toxin (BTX). For example, intramuscular injections of BTX produce local relaxation of treated muscles by inhibiting the release of acetylcholine, a neurotransmitter that is present at the junctions of nerve and muscle cells and that regulates the delivery of messages from neurons to muscle fibers.

Chorea: Jerky, irregular, relatively rapid involuntary movement that primarily involves muscles of the face or extremities. Choreic movements are relatively simple and discrete or highly complex in nature. Although involuntary and purposeless, these movements are sometimes incorporated into deliberate movement patterns. When several choreic movements are present, they often appear relatively slow, writhing, or sinuous, resembling athetosis. Chorea may occur in association with certain neurodegenerative diseases, including Wilson's disease and Huntington's disease, or systemic disorders, such as lupus. In addition, chorea is a dominant feature in Sydenham's chorea or may result from the use of certain medications, such as particular anticonvulsant or antipsychotic agents.

Chorionic villus sampling (CVS): A screening and diagnostic procedure performed during which tissue samples are obtained from a portion of the placenta using a specially guided needle via ultrasound. The placenta is the organ attached to the lining of the uterus that links the blood supplies of the developing fetus and the mother. The tissue sample is obtained from the layer from which the chorionic villi develop. Blood from the fetus flows through the umbilical cord to the placenta and enters minute blood vessels arranged in multiple "thread-like" projections or chorionic villi surrounded by maternal blood. Tissue samples obtained during chorionic villus sampling are analyzed to detect certain genetic or chromosomal abnormalities.

Chromosome: A chromosome is a thread-like structure made up of DNA and proteins. Each chromosome is like a string of beads, where each bead represents a different gene. There are 46 chromosomes, 23 pairs, in the nucleus of human cells.

Circadian: A rhythm of biological functions occurring in a 24-hour periodic cycle (e.g., sleeping, eating, etc.).

Clinical Global Impression (CGI): The CGI is a scale to assess s patient’s response to treatment. At baseline, the doctor rates how much the disease or illness impacts a patient’s life. The patient receives the treatment, or, in some cases, a certain amount of time passes, and the doctor again rates the impact of the disease or illness, this time as very much improved, much improved, minimally improved, no change, minimally worse, much worse, or very much worse.

Clinical trial: A clinical trial is a research study that tests how safe or how well a drug or treatment works in humans.

Clonus: movements characterized by alternate contractions and relaxations of a muscle, occurring in rapid succession. Clonus is frequently observed in conditions such as spasticity and certain seizure disorders.

Co-contraction: The simultaneous contraction of agonist and antagonist muscles.

Cognition: Cognition involves thinking skills such as perception, memory, awareness, reasoning, judgment, intellect, and imagination.

Cognitive impairment: Cognitive impairment is a decrease in the ability to process, learn, and remember information.

Cognitive therapy: Cognitive therapy is a method of treating psychiatric disorders that focuses on revising a person's thinking, perceptions, attitudes, and beliefs.

Cogwheel rigidity: Cogwheel rigidity is stiffness of muscles around a joint. If a person has Cogwheel rigidity, and another person tries to bend and straighten his elbow, it will not move smoothly. It will be a jerky movement. Imagine the wheels of a clock moving against each other. They don’t glide past each other. Instead they move one notch at a time, and then stop. This is what Cogwheel rigidity looks like. It is a motor symptom of Parkinson’s disease.

Complementary and alternative medicine: Complementary and alternative medicine, as defined by National Institutes of Health, is a group of diverse medical and health-care systems, practices, and products that are not presently considered to be part of conventional medicine

Composite Autonomic Scoring Scale: The Composite Autonomic Scoring Scale is a battery of validated, sensitive, and specific tests for the assessment of autonomic nervous systems, resulting in a 10-point composite score.

Computerized tomography (CT) imaging or scanning: An advanced diagnostic scanning technique during which cross-sectional images of tissues and organs are produced by passing x-rays through the body at various angles. In some cases, a contrast medium, which is opaque on x-rays, may be injected intravenously to produce enhanced images of certain tissues, organs, or blood vessels.

COMT inhibitors: Drugs that block catechol-O-methyltransferase, an enzyme that breaks down dopamine. COMT inhibitors include entacapone (Comtan®) and tolcapone (Tasmar®).

Congenital: Existing at birth.

Constipation: Constipation is a change in bowel movements from normal. Bowel movements are infrequent or the stool becomes hard and dry. It becomes difficult to pass the stool.

Contractures: Fixed resistance to passive stretching of certain muscles due to shortening or wasting (atrophy) of muscle fibers or the development of scar tissue (fibrosis) over joints.

Contralateral: the opposite side. For example, during brain surgery for essential tremor, if the surgery is performed on the right side of the brain, the left side of the body will be affected.

Controlled-release formulation: A form of a drug (e.g., L-dopa) that is absorbed slowly by the digestive system, prolonging the duration of effect of each dose.

Conversion disorder: A conversion disorder is a condition in which people have neurologic symptoms such as numbness, paralysis, or seizures, but no neurologic cause of the symptoms can be found. These problems arise in response to difficulties in the person's life. A conversion disorder is considered to be a psychiatric disorder.

Corticobasal degeneration (CBD): A slowly progressive disorder characterized by neurodegenerative changes of certain brain regions, including the cerebral cortex (particularly the frontal and parietal lobes) and parts of the basal ganglia. Most patients initially develop symptoms in their 60s or 70s. Primary findings may include stiffness (rigidity); slowness of movement (bradykinesia); loss of the ability to coordinate and execute certain purposeful movements of the arms or legs (limb apraxia); the sensation that a limb is not one's own ("alien limb phenomenon"); and other sensory abnormalities. Affected individuals may also develop slurred, labored speech (dysarthria); dystonia; and irregular, involuntary, "shock-like" contractions of certain muscle groups, particularly of the hands and forearms, that may be provoked or aggravated by voluntary movement and certain external stimuli (action and reflex myoclonus).

Corticospinal: Referring to or connecting the outer region of the brain (cerebral cortex) and the spinal cord.

Corticosteroid agents: Synthetic medications similar to corticosteroid hormones, which are naturally produced by the outer regions of the adrenal glands (adrenal cortex). Corticosteroid agents may be prescribed to treat inflammatory conditions; as long-term therapy to suppress the immune system (immunosuppressive therapy) in order to prevent rejection of a transplanted organ; as hormone replacement therapy for those with insufficient levels of natural corticosteroid hormones; or as therapy for other conditions. High dose, long-term corticosteroid therapy may result in various adverse effects, including an increased susceptibility to infection; osteoporosis, a bone disorder characterized by a progressive loss of bone mass; high blood pressure (hypertension); tissue swelling (edema); or retarded bone growth in children.

Cranial: Of or from the cranium or skull.

Cranial nerve nuclei: Specialized groups of nerve cells (nuclei) that give rise to and convey or receive impulses from sensory and motor constituents of the cranial nerves, which are the 12 pairs of nerves that emerge from the brain. These nerve pairs convey sensory impulses for various functions including taste, smell, hearing, and vision; motor impulses involved in controlling eye movements, chewing, swallowing, facial expressions, etc.; and impulses for transmission to certain organs and glands for regulation of various involuntary or autonomic activities.

Cranial neuropathy: Disease or damage of a cranial nerve or nerves. The cranial nerves are the 12 nerve pairs that arise directly from the brain and are involved in conveying impulses for various functions including smell, hearing, vision, and taste; pupil contraction; eye movements; facial expressions; movements of the tongue, head, and shoulders; etc. Cranial neuropathy may result in associated muscle weakness; abnormal sensations, such as numbness, tingling, or pain; or other findings. Specific symptoms depend upon the specific nerve(s) affected.

Creutzfeldt-Jakob disease (CJD): A rare, degenerative, life-threatening brain disorder characterized by severe, progressive dementia; visual disturbances; muscle weakness; and abnormal involuntary movements, such as sudden, brief, "shock-like" muscle spasms (myoclonus), tremor, and relatively slow writhing motions that appear to flow into one another (athetosis). Although CJD usually appears to occur sporadically, about 10 percent of cases are familial, potentially suggesting a hereditary predisposition to the disease. In rare cases, CJD may also result from exposure to contaminated surgical instruments during brain surgery and was reported in the past due to therapy with pituitary-derived human growth hormone. In addition, a variant form of CJD (V-CJD) has been reported primarily in the United Kingdom; V-CJD has been potentially linked to consumption of beef from cows with bovine spongiform encephalopathy or BSE (so-called "mad cow disease"). Evidence suggests that CJD may be caused by mutations in the human prion* protein gene or contamination with abnormal prion protein. (*The term "prion" was named for "protein infectious agent.") Changes in the prion protein appear to lead to distinctive neurodegenerative abnormalities, i.e., relatively small, round, "sponge-like" (spongiform) cavities or gaps in certain brain regions. CJD and BSE belong to a group of related neurodegenerative disorders categorized as "transmissible spongiform encephalopathies."

Crossreact: Refers to the interaction of an antibody with an antigen that did not specifically or originally trigger its production. For example, in an abnormal autoimmune reaction, an antibody that was initially formed in response to an invading bacterium may inappropriately react against certain of the body's own tissues that contain some of the same amino acid sequences as within the microorganism.

Cytokine: Cytokines are small proteins that regulate the body’s immunity, inflammation, and blood-cell production responses.

Cytoplasm: The cytoplasm is the part of the cell that surrounds the nucleus.

DC inhibitors: Drugs that block decarboxylase, one type of enzyme that breaks down dopamine. Also called AADC inhibitors, they include carbidopa and benserazide.

Decarboxylase: Decarboxylase is a type of enzyme that removes a part of chemicals. This stops the chemical from working. Decarboxylase breaks down Levodopa in the body, keeping it from working in the brain. Carbidopa stops the decarboxylase from working. This allows Levodopa to get to the brain without being broken down.

Deep brain stimulation: Deep brain stimulation (DBS) involves an operation in which a neurosurgeon (a medical doctor who specializes in surgery on the brain, spine, and other parts of the nervous system) places very thin wires through tiny holes in the skull into the area of the brain that controls movements. These wires, called leads or electrodes, are connected to an insulated wire (extension) that is tunneled under the skin and connected to a battery-operated device called a neurostimulator. The surgeon sews the neurostimulator, which is about the size of a stopwatch, under the skin of the chest or abdomen. The device sends electrical pulses or signals through the wires to targeted areas in the brain, thereby blocking the abnormal nerve signals that cause the symptoms of Parkinson disease, essential tremor, or dystonia. A physician or nurse uses a remote controller to transmit radio signals to adjust the electrical pulses generated by the neurostimulator.

Degenerative: Marked by or pertaining to deterioration; particularly, deterioration of the function or structure of tissue or changes from a higher to a lower or less functionally active form.

Delirium: A state of frenzied excitement or wild enthusiasm.

Delusion: A delusion is a false belief that a person has either about himself or the world. The key to a delusion is that the person believes it no matter what. Even when someone shows evidence that the belief is not true, it doesn’t change the person’s belief.

Dementia: Dementia is not a disease but a group of symptoms. It is a loss of mental processes such as memory, language, or the ability to think. The loss is significant enough to cause problems with daily or social function, and becomes worse over time. Dementia is also characterized by personality changes.

Dendrites: The relatively narrow, branching projections that extend from the cell bodies of neurons. Nerve cells may contain multiple dendrites, which are stimulated by neurotransmitters, receive impulses from the nerve fibers (axons) of other neurons, and convey them toward their nerve cell bodies.

Dentatorubropallidoluysian atrophy: A rare genetic disorder that is most commonly described in Japan. Associated symptoms may become apparent in adolescence or adulthood. Early-onset disease may be characterized by rapidly progressive neurodegenerative changes, including seizures, cognitive impairment, and brief, "shock-like" muscle spasms of certain muscles or muscle groups (myoclonus). Late-onset disease may be associated with progressively impaired control of voluntary movement (ataxia) and symptoms often seen in Huntington's disease (HD), including chorea and gradual loss of thought processing and acquired intellectual abilities (dementia). Brain imaging studies typically reveal degenerative changes of the globus pallidus and specialized nerve cell clusters within the cerebellum (dentate nucleus). Similar to HD, the disorder may result from abnormally long sequences or "repeats" of particular coded instructions (unstable expanded CAG repeats) within a gene (located on chromosome 12).

Depression: Depression is a disease. A person with depression cannot talk themselves out of the disease. Depression is characterized by many symptoms including either a depressed mood or loss of interest in things that normally give pleasure. A person with depression also experiences weight loss or gain, fatigue, and feelings of worthlessness or guilt. Depression also causes a person to sleep and move around either too much or not at all.

Detoxification: Detoxification is the process of removing or neutralizing toxins in the body

Diaphragm: The dome-shaped muscle that separates the chest and abdomen. The diaphragm plays an essential role in breathing, contracting when air is drawn into the lungs and relaxing upon exhalation.

Differential diagnosis: Distinguishing between two or more diseases and conditions with similar symptoms by systematically comparing and contrasting their clinical findings, including physical signs, symptoms, as well as the results of laboratory tests and other appropriate diagnostic procedures.

Diuretics: Medications that promote the excretion of urine. Such medications are often prescribed to help reduce excess fluid levels in the body, such as associated with chronic heart failure, high blood pressure (hypertension), or certain kidney (renal) or liver (hepatic) disorders. Diuretics help to remove excess water from the body by increasing the amount that is excreted as urine.

DNA: Deoxyribonucleic acid. DNA is a spiraling, ladder-like (helical) molecule that is the carrier of the genetic code. Nucleic acids are the primary components of the chromosomes within the nuclei of cells. DNA is also found in mitochondria, the rod-like structures outside the nuclei of cells that function as a primary source of cellular energy.

Dopamine: Dopamine is a type of neurotransmitter--a chemical that nerve cells use to communicate with other nerve cells. Dopamine is especially important in nerve cells that send messages about movement.

Dopamine agonist (DA): A dopamine agonist is a substance that acts like dopamine. It can be a medication that produces the same effects in the brain that dopamine does.

Dopamine autoreceptor: A type of dopamine receptor that acts like a thermostat, preventing excess dopamine release as levels rise.

Dopamine receptor: A molecule on a receiving nerve cell (neuron) that is sensitive (or receptive) to stimulation (arousal) by dopamine or a dopamine agonist. At least five types have been identified including D1, D2, D3 receptors and the dopamine autoreceptor.

Dopamine receptor antagonist: A pharmacologic agent that binds to and blocks the action of dopamine receptors, essentially hindering receptor activity by preventing stimulation by dopamine.

Dopamine transporter: Dopamine is a chemical in the body that allows one nerve cell to send a message or signal to another nerve cell and helps to control movement. After dopamine finishes sending its message, a substance called a dopamine transporter carries the dopamine back from the nerve ending to the cell that produced it so that the dopamine can be reused. The number of dopamine transporters is a sign of the number of nerve endings that produce or release dopamine.

Dopaminergic: Dopaminergic is a word used to describe a chemical or a drug that either acts like or involves dopamine.

Dopaminergic drug: A dopaminergic drug is any drug that has the effect of dopamine. Levodopa is converted in the body to dopamine, and dopamine agonists mimic the effects of dopamine at the receptors.

Dopaminergic dysfunction: Malfunction of dopamine receptors.

Double-blind trial: A double-blind trial is a clinical experiment in which neither the patients nor the researchers are aware of which patients are receiving an active treatment and which, if any, are receiving placebo.

Duodenum: The duodenum is the part of the small intestine that is connected to the stomach.

Dysarthria: Dysarthria means difficulty forming words or speaking them. It could be caused by a problem in the brain or with the muscles used for speech. As a result, speech can be slurred or slowed and difficult to understand.

Dysesthesias: Unpleasant sensations that are produced in response to normal stimuli.

Dyskinesias: Dyskinesia, from the Greek words—dys (difficulty) and kinçsis (movement)—technically means any difficulty with movement. In Parkinson disease, the term refers to a jerky dancelike movement of the head and arms that may occur after several years or more of treatment with levodopa.

Dyskinesias while awake (DWA): Uncontrolled, sporadic movements of the legs and, in some cases, the arms. These movements may be very rapid (myoclonic) or quite slow and prolonged (dystonic); they usually disappear upon voluntary action. Some researchers suspect that these movements may represent a wakeful form of periodic limb movements in sleep (PLMS).

Dysphagia: Difficulty in swallowing. Dysphagia may be associated with esophageal obstruction as well as certain neurodegenerative or motor disorders involving the esophagus.

Dyspraxia: Partial loss of the ability to coordinate and perform certain purposeful movements and gestures in the absence of motor or sensory impairments.

Dystonia: Dystonia is a neurologic movement disorder characterized by lasting muscle tightening, or contractions. The contractions result in repeated twisting or writhing movements and unusual postures or positioning that the person with dystonia cannot control. Dystonia may be limited to specific muscle groups (focal dystonia), such as dystonia affecting muscles of the neck (cervical dystonia or spasmodic torticollis) or the eyes, resulting in closure of the eyelids (blepharospasm). Dystonia is associated with certain underlying genetic disorders, such as dystonia musculorum deformans, dopa-responsive dystonia, and paroxysmal kinesigenic and paroxysmal non-kinesigenic dystonic choreoathetosis. The condition may result from the use of certain medications, lack of oxygen during or immediately after birth, or other causes of brain trauma.

Dystonic: Referring to dystonia; sudden jerky or repetitive movements and muscle spasms due to impaired muscle tone and abnormal muscle rigidity.

DYT-1 dystonia: The DYT-1 gene regulates or "encodes" production of a protein called torsinA. Although its specific function is not know, torrsinA appears to be related to a class of proteins that enable cells to recover from injury or stress. The change, or mutation, that causes DYT-1 dystonia involves one of a pair of three basic chemical "building blocks" of DNA. These are called guanine, adenine, and guanine, or "GAG" trinucleotides and are part of the genetic code within the DYT-1 gene. The specific mutation that occurs in DYT-1 dystonia is an absence, or deletion, of GAG. This relatively tiny change in the blueprint for torsinA apparently causes critical changes in the function of the protein and may lead to the symptoms of dystonia.

Echocardiogram: An echocardiogram is a medical test that is used to study the structure and function of the heart. A computer captures echoes that are created from sound waves (ultrasound).

Economic burden: Economic burden involves both direct medical costs such as expenditures for drugs, physicians, and institutions, as well as indirect costs due to lost wages from illness, premature death, and disability.

Edema: Fluid accumulation in the tissues causing swelling

Edentulousness: lack of permanent teeth.

Effector organs: Organs that produce a nerve-stimulated effect, such as a muscle contraction or glandular secretion.

Electrical stimulation (ES): A test in which a small electrical charge is applied to a muscle via a needle to determine the level of muscle responsiveness.

Electrocardiogram (ECG, EKG): A noninvasive, diagnostic test that assesses the electrical activity of the heart muscle (myocardium). The heart's conduction system transmits electrical impulses that serve to coordinate contractions of the heart. During an ECG, the electrical activity of the cardiac conduction system is translated into recordings that assist in evaluating any abnormal alterations. The test may be administered while a patient is at rest or performing certain designated exercises. ECGs may help to detect or characterize cardiac conduction defects, abnormal heart rhythms (arrhythmias), enlargement (cardiac hypertrophy), or localized damage in heart muscle.

Electroencephalography (EEG): A noninvasive, diagnostic technique that records the electrical impulses produced by brain cell activity. An EEG reveals characteristic brain wave patterns that may assist in the diagnosis of particular neurologic conditions, such as seizure disorders, impaired consciousness, and brain lesions or tumors.

Electromyography (EMG): A diagnostic test that records the electrical responses of skeletal muscles while at rest and during voluntary action and electrical stimulation. During this test, a small needle is inserted into a muscle to record the level of activity.

Electron microscopy: An electron microscope beams electrons, instead of light beams, to magnify an object, providing very detailed images that are approximately 1000 times the magnification of a typical light-beam microscope.

Electrophysiologic recording : Electrophysiologic recordings include the study of the electrical activity associated with a specific body function (e.g., electromyogram [muscles], electroencephalogram [brain waves], etc.).

Electrophysiologic studies: The study of the electrical activity associated with a specific body function (e.g., EMG, EEG, etc.).

Encephalitis: Inflammation of the brain. Encephalitis is most commonly caused by certain viral infections or may occur subsequent to prior infection due to immune reactions that indirectly result in inflammation (postinfectious encephalitis). Although associated symptoms and findings may be variable, features may include fever, headache, irritability, listlessness (lethargy), and weakness. Some affected individuals may also develop confusion, disturbances of speech and memory, abnormal involuntary movements, paralysis of one side of the body, seizures, and/or coma. For those with involvement of the protective membranes enclosing the brain and spinal cord (meningitis), characteristic findings may include nausea, vomiting, stiffness of the neck, abnormal sensitivity to light (photophobia), and/or other symptoms.

Encephalopathies: Any abnormal conditions or diseases of the structure or function of the brain, particularly chronic, degenerative conditions.

Endogenous opiate system: A morphine-like substance that is produced within the body.

Endoplasmic reticulum (ER): The ER consists of a membrane system that branches out through the cytoplasm and includes rough ER, which is found in eukaryotic cells and contains ribosomes, and smooth ER, which is biochemically similar to rough ER but lacks ribosomes.

Endoscopy: A study in which the doctor looks inside the stomach or intestine using a hollow, thin, flexible tube that has a lens or miniature camera on the end of it.

Endotoxin: An endotoxin is a poisonous substance that is released from bacteria after the bacteria die or break apart.

Enzyme: An enzyme is a protein made by the body’s cells. There are chemical reactions that occur all the time in the body. Enzymes either speed up or slow down these reactions. Enzymes are not used up or permanently changed during the process.

Epidemiological study: examination of the distribution of disease as well as the determining factors related to specific diseases or health-related problems in a specific population.

Epidemiology : Epidemiology is the study of the patterns and causes of disease in groups of people.

Epworth Sleepiness Scale (ESS): The ESS is a paper-and-pencil test. In this test, you record how likely you are to fall asleep in seven different situations: sitting and reading, watching TV, sitting inactive in a public place (such as at a theater or in a meeting), as a passenger in a car for an hour without a break, Lying down to rest in the afternoon when circumstances permit, sitting and talking with someone, sitting quietly after a lunch without alcohol, while driving a car, while stopped for a few minutes in traffic.

Eradication: Eradication is the process of permanently eliminating something.

Ergot: A plant alkaloid produced by the fungus Claviceps purpurea.

Ergot-derived medication: A medication that has a chemical structure based on ergot, a plant alkaloid produced by a fungus called Claviceps purpurea. Permax® and Parlodel® are examples of ergot-derived medications that may be used to treat certain neurologic movement disorders.

Esophageal atony: Lack of normal muscle tone within the esophagus, the muscular tube that transports food from the throat to the stomach.

Essential tremor (ET): A common, slowly and variably progressive neurologic movement disorder characterized by involuntary, rhythmic, "back and forth" movements (i.e., tremor) of a body part or parts. In ET patients, tremor is primarily a "postural" or "kinetic" tremor or may be a combination of both types: i.e., tremor occurs while voluntarily maintaining a fixed position against gravity (postural tremor) and/or when conducting self-directed, targeted actions (kinetic intention tremor). In many individuals with ET, both hands are affected, although the condition may sometimes initially be noted in the dominant hand. ET also frequently affects the head, with tremor occurring in a "no-no" horizontal pattern in about three quarters of patients and the remainder affected by vertical "yes-yes" tremors. Less commonly, patients have tremor involving the voice, tongue, or roof of the mouth (palate), leading to impaired articulation of speech (dysarthria). Rarely, tremor may affect the trunk or lower limbs, particularly with advanced stages of disease. ET may appear to occur randomly for unknown reasons (sporadically) or be transmitted as an autosomal dominant trait.

Estrogen: (1) Any of several, naturally occurring female sex hormones that promote the development of female secondary sexual characteristics and the proper functioning of the reproductive system; (2) synthetically produced agents used in birth control pills (oral contraceptives) or in the treatment of symptoms of menopause; osteoporosis, which is a bone disorder characterized by a progressive loss of bone mass; particular types of advanced postmenopausal breast cancer and prostate cancer; and other conditions.

Eukaryotic: Meaning literally "true nucleus," eukaryotic organisms include protists, plants, animals and fungi, all of which have separate membrane-bound nuclei that contain genetic material (mDNA).

Excessive Daytime Sleepiness (EDS): EDS is more than the normal amount of sleepiness during the day, along with a lack of energy, even after a normal night's rest. EDS may be measured using the Epworth Sleepiness Scale.

Executive function: Executive function refers to a person’s ability to establish a goal and then make decisions and put into action activities to meet that goal.

Exon: An exon is a region of a gene that contains part of the code for producing the gene's protein. Each exon codes for a specific portion of the complete protein. Exons are separated by long regions of DNA (called introns or sometimes "junk DNA") that have no apparent function.

Extrapyramidal system: Refers to central nervous system structures (i.e., outside the cerebrospinal pyramidal tracts) that play a role in controlling motor functions. The extrapyramidal system includes substructures of the basal ganglia and the brainstem and interconnections with certain regions of the cerebellum, cerebrum, and other areas of the central nervous system. Extrapyramidal disturbances may result in postural and muscle tone abnormalities as well as the development of certain involuntary movements.

Fatigue: Fatigue is a feeling of tiredness or a sense of having low energy that may lead to a decrease in a person's ability to perform work or daily activities.

Feldenkrais: Feldenkrais is a method of improving the body’s ability to function, learn, and change by increasing awareness of movement, posture, and breathing.

Ferritin: A serum ferritin level is a blood test that measures the amount of ferritin in your cells. Ferritin is a protein that stores iron inside your cells so that your body can use the iron when it is needed. The amount of ferritin stored, or your serum ferritin level, reflects the amount of iron that is stored in your body. Symptoms of RLS have been shown to be increased in people who have low ferritin levels.

Festinating Gait: A person with a festinating gate will take very small steps. His feet never come all the way off the floor, so it looks like the person is shuffling along. The person cannot control the shuffling or take bigger steps.

Fibrosis: Build-up of fibrous tissue in an abnormal place in the body

First-, second- and third-degree relatives: First-degree relatives include your mother, father, sisters, brothers, sons, and daughters. Second-degree relatives are your aunts, grandmothers, uncles, and grandfathers. Third-degree relatives include your great-grandmothers, great-aunts, great-uncles, and first cousins.

First-degree relatives: First-degree relatives include a person’s mother, father, brothers, sisters, sons, and daughters who are related by blood and not through adoption or marriage.

Flexion: The act of bending (as opposed to extending) a joint.

Focal dystonia: Focal dystonia is a type of dystonia that is limited to a specific group of muscles. Some types of focal dystonia involve muscles that control movement of the neck (cervical dystonia), eyes (blepharospasm), hand (writer’s cramp or musician’s dystonia), or vocal cords (spasmodic dysphonia).

Food and Drug Administration (FDA): The FDA is a federal agency charged with ensuring that the food supply in the United States is safe and wholesome, that cosmetics are not harmful, and that medicines, medical devices, and radiation-emitting consumer products are safe and effective.

Free radicals: Unstable molecular fragments that can damage cells. One hypothesis holds that free radical formation in the substantia nigra causes the loss of nigral cells (leading to Parkinson's disease).

Freezing: Freezing is when motion is halted. It looks like the person is nailed to the floor and can’t move forward.

Frequency: number of cycles or repetitions within a fixed unit of time such as the number of cycles per second (Hertz or Hz). For example, essential tremor is typically 4 to 12 Hz.

Friedreich's ataxia: Friedreich's ataxia is the most common autosomal recessively inherited type of ataxia. Like the autosomal dominant spinocerebellar ataxias, the main symptoms are loss of coordination and unsteadiness of gait. Other systems may also be affected and people with Friedreich's ataxia should be monitored for heart disease and diabetes. The affected protein is called frataxin, and is thought to be involved in iron metabolism.

Froment's sign: Increased resistance to passive movements of a limb that may be detected upon voluntary activity of another body part.

Functional Magnetic Resonance Imaging (fMRI): A noninvasive, diagnostic scanning procedure that produces detailed, computerized images. The use of a "contrast agent" or dye enhances the detail of the images. Sequencing of these images may help physicians visualize the body's functioning, thus aiding differential diagnosis.

Gait: Gait is the style or manner of walking. Gait disturbances may be associated with certain neurologic or neuromuscular disorders, orthopedic conditions, inflammatory conditions of the joints (i.e., arthritic changes), or other abnormalities.

Gait apraxia: Loss of the ability to consciously sequence and execute the movements required to coordinate walking. Gait apraxia may result in unsteady walking patterns; "toe-walking"; a widely based, jerky gait; and balance difficulties.

Gamma knife radiosurgery: a highly specialized technique using a device that produces ionizing radiation to produce a lesion in the target tissue. This device focuses a beam of high intensity irradiation to a targeted area and is used as localized therapy to treat individuals with certain brain diseases (e.g., brain tumors, certain movement disorders, etc.).

Gamma-aminobutyric acid (GABA): An amino acid neurotransmitter that inhibits or decreases the electrical activities of nerve cells. GABA is the primary inhibitory neurotransmitter in the brain.

Gastroesophageal reflux: Backflow of stomach contents into the esophagus. This condition may be chronic and cause weakness of the lower esophageal sphincter, the ring-shaped muscle located at the junction of the esophagus and stomach.

Gastrointestinal: Gastrointestinal refers to the stomach and small and large intestines, as well as to the mouth, esophagus, anus, and related organs.

Gastrostomy tube: A plastic tube inserted into the stomach through a surgical incision in the abdomen. A gastrostomy tube is used to deliver liquified food to the digestive system when swallowing becomes dangerous or difficult.

Gene: Genes are the smallest units of heredity. The information from all the genes, taken together, makes up the blueprint or plan for the human body and its functions. A gene is a short segment of DNA, which is interpreted by the body as a plan or template for building a specific protein.

Generic drug: A generic drug is a drug that has the same active ingredients as the brand-name drug. It works the same way a brand-name drug works, but is usually less expensive. Generic drugs meet the same FDA standards as brand-name drugs.

Genetic anticipation: A phenomenon in which the onset of symptoms of a hereditary disease appears to occur at a progressively earlier age in successive generations. Genetic anticipation has been demonstrated in a number of hereditary disorders (such as Huntington's disease, dentatorubropallidoluysian atrophy, etc.) in which the gene mutation consists of abnormally long sequences or "repeats" of particular coded instructions (e.g., unstable expansion of CAG repeats). With other disorders in which genetic anticipation has previously been suggested (e.g., essential tremor), studies have indicated that increased awareness of the condition in affected families may be responsible for earlier recognition of symptom onset.

Genetic heterogeneity: Manifestation of similar or the same observable characteristics or traits (i.e., phenotype) resulting from different genetic mechanisms, such as changes (mutations) of different genes or a combination of genes.

Germline mosaicism: The presence of a gene mutation for a disease trait in some yet not all of an individual's sexual reproductive cells (germ cells) within the ovaries or testes (gonads). Germline mosaicism is sometimes suspected when parents have more than one child with a genetic disorder transmitted as a dominant trait yet neither parent appears to be affected by the condition.

Gland: A gland is a structure or organ that makes a substance, such as a hormone or chemical, that is used elsewhere in the body. Some of these hormones and chemicals are insulin, bile, growth hormone, estrogen, and testosterone.

Gliosis: A proliferation of astrocytes in damaged areas of the central nervous system (CNS). Astrocytes are relatively large glial cells, which are the connective tissue cells of the CNS. Astrocytes have various functions, including accumulating in areas where nerve cells (neurons) have been damaged. Gliosis and neuronal loss in certain brain regions are findings seen in various neurodegenerative disorders.

Globus pallidus: A major substructure of the basal ganglia deep within the brain. Specialized groups of nerve cells in the globus pallidus function as an "intermediate relay system." This system processes and transmits information from the basal ganglia by way of the thalamus to areas of the brain that regulate complex motor functions (e.g., motor cortex, premotor area of frontal lobe).

Glottis: The slit-like opening between the vocal cords; the region of the voice box (larynx) consisting of the vocal cords and the opening between them.

Glutamate: An amino acid that is a primary excitatory neurotransmitter in the central nervous system. This chemical agent plays an essential role in initiating and transmitting nerve impulses, crossing synapses to stimulate postsynaptic neurons.

Gram staining: Gram staining is a method used to classify bacteria. In the first step of the process bacteria are stained with gentian violet and then treated with Gram solution (named after Dr. Gram, the inventor of the technique). After the bacteria have been decolorized with alcohol and treated with safranine, a red organic dye, and washed in water, those bacteria that keep the gentian violet are gram-positive and those that do not are gram-negative.

Gray matter: Nerve tissue that primarily consists of nerve cell bodies, dendrites, and unmyelinated axons, thus having a gray appearance. In contrast, white matter predominantly contains myelinated nerve fibers.

Half life: The half life of a drug is the time it takes for the blood level to decrease by half after a drug is stopped.

Hallervorden-Spatz disease: A slowly progressive hereditary disorder characterized by abnormal accumulations of iron pigments in certain regions of the basal ganglia (e.g., globus pallidus and substantia nigra). This autosomal recessive disorder typically becomes apparent during late childhood or adolescence. Associated symptoms may include progressive stiffness and resistance to movement (rigidity); increasing difficulties speaking and eating; sustained muscle contractions that result in repetitive twisting motions or unusual postures or positions (dystonia); the presence of multiple, irregular, jerky motions that may combine to appear flowing or writhing in nature (choreoathetosis); and/or other abnormalities.

Hallucination: A hallucination is something that a person sees, smells, touches, hears, or tastes but it is not really there. The hallucination is only present in the mind of the person. No one else experiences a hallucination because it is not a part of the environment.

Heat pain: Heat pain arises from warm or hot temperatures.

Hemichorea: Irregular, abrupt, relatively rapid involuntary (i.e., choreic) movements that are unilateral or involve muscle groups on one side of the body.

Hemidystonia: Hemidystonia is a form of dystonia that affects one side of the body or is characterized by unilateral involvement of the upper and lower limbs.

Hemizygote: Refers to a cell, organism, or individual with only one of a pair of genes for a specific trait. This term is often used to describe males who inherit one copy of an X-linked disease trait. It may also refer to the state in which genetic material is deleted from one member of a chromosomal pair.

Hereditary: Inherited; inborn; referring to the genetic transmission of a trait, condition, or disorder from parent to offspring.

Heredodegenerative: Pertaining to genetically transmitted (hereditary) neurologic disorders characterized by progressive neuronal loss and other neurodegenerative changes (e.g., associated gliosis). For example, the term "heredodegenerative dystonias" is used to refer to several, usually hereditary disorders in which neurodegenerative changes may lead to dystonia as a primary feature and other neurologic symptoms are typically present. However, in some patients with such disorders, dystonia may not always develop and other neurologic features may be primary findings. Disorders that have been categorized as heredodegenerative dystonias include ataxia-telangiectasia, Hallervorden-Spatz disease, Huntington's disease, Parkinson's disease, progressive supranuclear palsy, neuroacanthocytosis, and Wilson's disease.

Hertz (Hz): cycles per second.

Heterogeneity: comprising unrelated or differing parts or elements.

Heterozygous carriers: The term "heterozygosity" refers to the state of having different genes that occupy the same position (locus) on one or more paired chromosomes. "Heterozygous carriers" describes individuals who carry a single copy of a mutated gene for a disease trait, such as females who have a copy of a disease gene for an X-linked disorder. Because females have two X chromosomes yet only one functioning copy is necessary, a percentage of X chromosomes with the mutated gene may not be expressed, typically in a random pattern (known as "random X chromosome inactivation"). Therefore, females who are heterozygous for an X-linked disease trait often have no disease manifestations or less severe symptoms than affected males. However, because males have one X chromosome from the mother and one Y chromosome from the father, males who carry an X-linked disease trait will typically fully express the mutated gene. Rarely, females who are heterozygous for an X-linked disease trait may manifest symptoms with about the same severity as affected males.

Hoehn and Yahr Scale: The Hoehn and Yahr Scale is a commonly used physician-administered rating of the global severity of the motor symptoms of Parkinson's disease. Scores range from 0, no signs of disease, to 5, wheelchair bound or bedridden without assistance.

Homeopathy: Homeopathy is a system of medicine that is based on the Law of Similars, a belief in which substances that cause healthy people to exhibit symptoms can, conversely, be used to restore the body to health.

Homeostasis: Homeostasis exists when an organism’s internal state of being is in balance even when the external environment is changing.

Homocystinuria: A metabolic abnormality characterized by excessive amounts of the amino acid homocystine in the urine. Homocystinuria, which may be transmitted as an autosomal recessive trait, may result from deficient activity of certain enzymes involved in the metabolic conversion of the amino acid methionine to cysteine. Associated symptoms and findings often include developmental delay; dislocated lens of the eyes (ectopia lentis); thin, weak muscles; progressive mental retardation; psychiatric abnormalities; skeletal defects; blockage of a blood vessel by a piece of a blood clot (thrombus) carried in the bloodstream (thromboembolism); and/or other abnormalities.

Huntington disease: Huntington disease (HD) causes a specific type of nerve cells in the brain to die off. In the early stages of the disease, symptoms may include slight personality changes, forgetfulness, clumsiness, and "fidgeting" movements of the fingers, eyes, or toes. As HD becomes worse, it may cause memory, thinking, behavior, and planning problems, as well trouble talking, swallowing, and walking. HD is an autosomal-dominant inherited condition, meaning that if one of your parents has HD, you have a 50-50 chance of getting it. A blood test can tell you if have the HD gene and will develop the disease. Genetic counseling can help you weigh the risks and benefits of taking the test. There is no cure for HD, but some medicines may help with the symptoms.

Huntington’s Disease-like 2 (HDL2): This rare disease strongly resembles Huntington’s disease in its inheritance and symptoms, which include abnormal movements, personality changes, and changes in the ability to think and process information. HDL2 is due to damage to the same parts of the brain as in HD; however, it is caused by mutation of a different gene, and also has an increased number of repeats. To date, almost all affected families have been of African ancestry. The other “Huntington’s disease-like” disorders (types 1, 3, and 4) are even rarer and have only been reported in one family each.

Hyperglycemia: An abnormally high level of the simple sugar glucose in the blood.

Hyperkalemic: Pertaining to hyperkalemia, a condition characterized by unusually high concentrations of potassium in the blood. Potassium, a positively charged ion, helps to regulate water balance, nerve conduction, and muscle contraction. Hyperkalemia may lead to various signs and symptoms, such as diarrhea, nausea, abdominal cramps, weakness, and, with increasing severity, abnormal heart rhythms and muscle paralysis.

Hyperkinetic: Characterized by excessive movement because of abnormally increased motor activity or function. Certain movement disorders are termed "hyperkinetic" such as tics or essential tremor.

Hypertension: Hypertension, also referred to as high blood pressure, is an abnormal increase in the pressure of blood against the walls of the arteries. Hypertension may be essential, meaning that it has no known cause, or may be related to another disease such as kidney disease or diabetes.

Hyperthyroidism: a condition caused by the effects of too much thyroid hormone on tissues of the body.

Hyperventilation: Abnormally rapid breathing usually accompanied by air swallowing. Hyperventilation results in excessive intake of oxygen and increased elimination of carbon dioxide, which may eventually lead to a disturbance in the body's acid-base balance.

Hypnagogic hallucinations: Hypnagogic hallucinations are vivid, realistic, often frightening dreams that occur while the person is falling asleep or immediately upon awakening.

Hypocretin: Hypocretin (also known as orexin) 1 and 2 are neuropeptides. These protein-like molecules are found in the brain and act as hormones or neurotransmitters. They are involved in the regulation of sleep and wakefulness.

Hypokalemic: Referring to hypokalemia, which is characterized by abnormally low potassium levels in the blood. Potassium, the primary positively charged ion (cation) of muscle, plays an important role in regulating muscle contraction, nerve conduction, and other bodily functions. Hypokalemia may result in confusion, fatigue, weakness, and, in severe cases, paralysis and heart rhythm abnormalities.

Hypokinesia: Hypokinesia is decreased movement. It comes from two Greek words—hypo and kinçsis—hypo means decreased, and kinçsis means movement.

Hypomimia: Hypomimia is reduced facial expressions. This can be caused by weakness or paralysis of facial muscles.

Hypoparathyroidism: An endocrine condition characterized by insufficient secretion of parathyroid hormone due to injury, disease, or congenital abnormalities of the parathyroid glands. Parathyroid hormone plays an essential role in regulating calcium balance in the body. Hypoparathyroidism results in low calcium blood levels (hypocalcemia), leading to various symptoms and findings. For example, hypoparathyroidism may cause a condition known as tetany in which increased excitability of nerves and muscles results in uncontrollable, painful muscle spasms and cramping; abnormal involuntary movements resembling chorea; spasmodic closure of the larynx (laryngospasm); and other findings. Hypoparathyroidism may also lead to seizures; abnormal calcium deposits (calcifications) in the basal ganglia; loss of transparency of the lenses of the eyes (cataracts); dry, scaly skin; weakened tooth enamel; and/or other abnormalities.

Hyposmia: Hyposmia refers to a decreased sense of smell.

Hypotension: Hypotension is low blood pressure. It comes from two Greek words—hypo and tension—hypo means low and tension means pressure.

hypoxia: abnormally low levels of oxygen

Iatrogenic: a disease or disorder that is induced inadvertently by a physician or surgeon or by medical treatment or diagnostic procedures.

Idiopathic: A disorder or condition of spontaneous origin; self-originated or of unknown cause. The term is derived from the prefix "idio-" meaning one's own and "pathos" indicating disease.

Idiopathic epilepsy: Recurrent seizures of unknown origin or cause; repeated episodes of uncontrolled electrical activity in the brain that occur in the absence of detectable brain lesions. Also known as essential or primary epilepsy, these conditions are often thought to have a genetic component. This may suggest that affected individuals have an inherited predisposition for recurrent seizures.

Illusions: Illusions occur when a person sees something that is real but misinterprets what it is.

Immunofluorescence: This technique uses antibodies linked to a light-emitting or fluorescent dye in order to study foreign substances in a tissue sample.

Immunogenicity: The ability to or the degree to which a particular substance may provoke an immune response; having the properties of an antigen or any substance that may trigger a particular immune reaction, such as the production of antibodies.

Implantable Pulse Generator (IPG): A device that is placed under the skin near the collarbone as part of a surgical procedure known as deep brain stimulation. Wire leads from electrodes implanted in the brain are connected to the pulse generator, which then delivers continuous high frequency electrical stimulation to the thalamus via the implanted electrodes. This form of stimulation probably "jams" the nucleus and therefore modifies the message in the movement control centers of the brain, serving to suppress tremor.

Incontinent: Incontinent usually refers means that a person has lost control over his or her bladder. It can also, however, mean that she has lost control of her bowel as well. A person will urinate or dribble urine when not using the toilet.

Inflammation: Inflammation is the body’s first response to injury or irritation. The classic signs of inflammation are pain, heat, redness, swelling, and loss of function.

Inheritance patterns: Each person inherits two copies of almost every gene, one from the mother and one from the father. Some diseases develop when only one copy of a gene is changed or mutated, even if the other copy is completely normal. Such a gene is passed from parent to child in an autosomal dominant inheritance pattern. A parent who has the mutation is probably affected by the disease. Each child of that parent has a 50% chance of inheriting the mutation and, thus, developing the disease. Other diseases develop only when both copies of a gene are mutated. In this case, the mutated gene is passed from both parents in an autosomal recessive inheritance pattern. Parents carrying one copy of the mutated gene are unaffected by the disease. Each parent must contribute one mutated gene to a child for the child to develop the disease. Each child has a 25% chance of inheriting both mutations and developing the disease.

Inhibition: The restraint, suppression, or arrest of a process or the action of a particular cell or organ; the prevention or slowing of the rate of a chemical or an organic reaction. The term "reciprocal inhibition" refers to the restraint or "checking" of one group of muscles upon stimulation (excitation) and contraction of their opposing (antagonist) muscles.

Inhibitor: A substance that blocks, restricts, or interferes with a particular chemical reaction or other biologic activity.

Innervate: To supply a body part, tissue, or organ with nerves or nervous stimulation.

Insidious: Of subtle, gradual, or imperceptible development; referring to the development of symptoms that may not be recognized by an affected individual until the disorder in question is established.

Insomnia: Insomnia is not being able to fall asleep or stay asleep for the night.

Intestine: The intestine is sometimes called the bowel or the gut. It is the part of the digestive system that extends from the stomach to the rectum. It is made up of the small and large intestines and serves to absorb water and nutrients from the food and liquids that we drink and eat. The small intestine extends from the stomach to the large intestine and is made up of three segments: the duodenum, the jejunum, and the ileum.

Intravenous: Within a vein or veins, as in introducing certain substances, such as fluids, nutrients, or medications, directly into a vein.

Involuntary: Involuntary means that a person does not have control over something. In the body, it means the things that a person does not have conscious control over.

Ion: An electrically charged atom or group of atoms due to the loss or gain of one or more electrons. Positively charged ions, known as cations, include potassium, calcium, sodium, hydrogen, ammonium, and magnesium. Negatively charged ions, called anions, include chloride, phosphate, and bicarbonate. The transfer of ions across cellular membranes plays an essential role in vital bodily processes, including enzyme activation, protein metabolism, acid-base balance, nerve impulse transmission, and muscle contraction.

Ischemia: Ischemia occurs when the flow of oxygen-rich blood to tissue in the body is reduced or stopped.

Isoleucine: an essential amino acid.

Jejunostomy tube: The jejunostomy tube is similar to a gastrostomy tube, although this tube is longer and is inserted through the abdominal wall into the jejunum, the middle section of the small intestine.

Joint contractures: Permanent flexing or extension of joints in fixed postures due to shortening of muscle fibers. Contractures, abnormal fixation of the limbs, and associated deformity may result from prolonged immobility of developing joints.

Juvenile myoclonic epilepsy: A form of idiopathic epilepsy or recurrent seizures of unknown origin, with symptom onset typically occurring from approximately 12 to 16 years of age. The condition is characterized by sudden, involuntary, "shock-like" muscle jerks (myoclonus) that primarily occur during the morning or with stress, fatigue, or alcohol consumption. Patients may later develop generalized tonic-clonic seizures associated with loss of consciousness and rhythmic contraction and relaxation of all muscle groups.

Kinesigenic: Caused by sudden voluntary movement; movement induced. More specifically, this term is often used to describe abrupt episodes of involuntary movement that are provoked by sudden motions or unexpected stimuli.

Lafora's disease: A progressive myoclonic encephalopathy (PME) that is inherited as an autosomal recessive trait. Associated symptoms typically begin in childhood or early adolescence and include frequent seizures characterized by loss of consciousness and rhythmic contraction and relaxation of all muscle groups (generalized tonic-clonic seizures); sudden, involuntary, "shock-like" muscle jerks (myoclonus); and rapidly progressive deterioration of thought processing and acquired intellectual abilities (dementia). Removal and microscopic examination of minute tissue samples (e.g., muscle fibers, liver cells, etc.) reveal abnormal, characteristic deposits of complex proteins and carbohydrates within the fluid portion of cells (intracytoplasmic inclusions known as "Lafora bodies").

Lance-Adams syndrome: Also known as "posthypoxic" or "postanoxic action myoclonus," this condition is characterized by the development of chronic action myoclonus due to a temporary lack or inadequate supply of oxygen to the brain (cerebral hypoxia or anoxia). Patients with action myoclonus experience sudden, involuntary, "shock-like" muscle contractions that may be triggered or aggravated by voluntary movement. Lance-Adams syndrome is also often associated with cerebellar ataxia or lack of coordination, postural imbalance, and other associated findings.

Laryngoscope: A laryngoscope is a long, thin, flexible tube that has a light and a small camera attached to the end. A doctor uses a laryngoscope to look at the larynx, or voice box.

Lateral: Sideways; of, on, from, or toward the side.

Leigh disease: A disorder of mitochondrial function that typically becomes apparent during infancy. Also known as subacute necrotizing encephalomyelopathy, the disorder may be characterized by feeding and swallowing difficulties, vomiting, muscle weakness, low muscle tone (hypotonia), and delayed acquisition of motor and language skills. Affected infants and children may also develop seizures; an impaired ability to coordinate voluntary movements (ataxia); involuntary, rapid, rhythmic eye movements (nystagmus); tremor; dystonia; and/or other abnormalities. The disorder, which has a number of underlying causes, may occur randomly for unknown reasons (sporadically) or be transmitted as an autosomal recessive or X-linked trait. Leigh disease is associated with characteristic changes of the central nervous system (CNS), including symmetric regions of localized tissue loss (necrosis) and neurodegenerative changes of the basal ganglia, thalamus, brainstem, spinal cord, and other regions of the CNS.

Leucine: an essential amino acid.

Levodopa: Levodopa is a drug used to treat Parkinson's disease. It is also called L-dopa and, in the United States, is sold as Sinemet. Levodopa crosses the blood-brain barrier and is converted by the body to dopamine. A loss of dopamine-producing nerve cells in the part of the brain that controls movements leads to the symptoms of Parkinson's disease.

Lewy body: A Lewy body is a mass of protein found in dying nerve cells in the brain.

Lewy Body Disease: Also called diffuse Lewy body disease, Lewy body dementia. Lewy body disease is a common cause of dementia, accounting for approximately 15%-20% of all cases. The age of onset is typically in the late 50s through the 70s. It is more common in men than women. Lewy Body Disease is characterized by more daily fluctuations in symptoms than Alzheimer's disease, as well as more prominent psychosis. Patients are prone to have adverse reactions to antipsychotics. Patients also have parkinsonian features early in the disease, including slowed movements and rigidity, though usually without tremor. The Lewy body is a protein aggregate found in dying neurons in the brain. In Lewy body disease, the Lewy bodies are most prominently found in the cortex, or surface of the brain, versus in the midbrain for Parkinson's disease.

Lipopolysaccharide: A lipopolysaccharide is a molecule made up of a lipid (a fat) with a polysaccharide (a complex sugar). In most circumstances, the terms lipopolysaccharide and endotoxin can be used interchangeably.

LRKK2: LRRK2 (pronounced as lark-two) stands for leucine-rich repeat kinase 2. It is the name of a gene that is responsible for providing instructions for making a protein called dardarin. The gene is thought to be active in the brain. Although little is known about the LRRK2 gene or dardarin protein, researchers do know that part of the LRRK2 gene provides instructions to make a protein segment that is rich in a protein building block (amino acid) called leucine. Proteins with leucine-rich regions appear to play a role in activities that require protein-protein interactions, such as transmitting signals or helping to assemble the cell's structural framework (cytoskeleton). Other parts of dardarin, such as a region called the WD40 domain, also indicate that dardarin is capable of multiple protein-protein interactions. Researchers also suspect that the dardarin protein has an enzyme activity known as kinase. Proteins with kinase activity assist in the transfer of a phosphate group (a cluster of oxygen and phosphate atoms) from the energy molecule ATP to amino acids in certain proteins. This phosphate transfer is called phosphorylation, and it is a necessary step in turning on and off many cell activities.

Lumbar puncture: A procedure during which a sample of fluid (i.e., cerebrospinal fluid [CSF]) is removed from the spinal canal for diagnostic or therapeutic purposes. During the procedure, CSF is obtained via a hollow needle inserted between two bones of the spinal column within the lower back (i.e., usually the third and fourth lumbar vertebrae). Laboratory analysis conducted on CSF may help to diagnose central nervous system infections, certain tumors, or particular neurologic disorders. In some cases, lumbar puncture may also be performed to inject certain medications into the CSF, such as particular anticancer (chemotherapeutic) agents.

Lysosomal: Referring to lysosomes, which are membrane-bound bodies (organelles) outside the nuclei of cells that contain various enzymes engaged in intracellular digestion.

Lysosomal storage diseases: Inborn errors of metabolism in which deficiency or impaired functioning of particular lysosomal enzymes leads to an abnormal accumulation of certain substances (e.g., fats, complex carbohydrates) within particular cells, progressively affecting multiple bodily tissues and organs. (Lysosomes are membrane-bound, enzyme-containing bodies within cells that engage in digestive processes; enzymes are proteins that accelerate the rate of certain chemical reactions in the body.) Most lysosomal storage disorders (e.g., mucolipidoses, mucopolysaccharidoses, lipidoses, etc.) are thought to be inherited as autosomal recessive traits.

Machado-Joseph disease: Machado-Joseph disease, also known as spinocerebellar ataxia (SCA) type III, is probably the most common autosomal dominant SCA. This disorder was previously known as Azorean disease, as a large number of Portuguese families from the Azores Islands were found to be affected; however, SCA type III has now been reported in many other ethnic groups. In addition to unsteadiness of gait (ataxia), symptoms may involve parkinsonism, dystonia, and chorea. The affected protein is called ataxin-3; however, its function is not yet known.

Magnetic resonance imaging (MRI): A diagnostic scanning technique during which radio waves and an electromagnetic field are used to help create detailed, cross-sectional images of specific organs and tissues. MRI is often considered a particularly valuable imaging technique for studies of the brain and spinal cord because of the MRI’s ability to scan images from various angles and provide strong contrast between healthy and abnormal tissues.

MAO inhibitors: MAO inhibitors are drugs that inhibit or prevent the action of an enzyme called monoamine oxidase (MAO). This enzyme helps to break down dopamine. When MAO is inhibited, the amount of time that dopamine acts in the brain is lengthened. Examples of MAO inhibitors that are used in the treatment of Parkinson disease include rasagiline, (Azilect®) and selegiline (Eldepryl®, Zelapar®).

MAO-B inhibitors: Inhibitors of the enzyme monoamine oxidase B. MAO-B helps break down dopamine; inhibiting it prolongs the action of dopamine in the brain.

Matched control subjects : Matched control subjects are people who have similar characteristics, such as age, height, weight, education, sex, or other characteristics, as the patients being studied, but they do not have the disease. In this study, the control subjects were matched with regard to age and sex to each person who had PD. The control subjects did not have PD, parkinsonism, or any other form of tremor.

Mean: An average; intermediate or middle position in value, quantity, or degree. The "arithmetic mean" is a statistical measure derived by adding a set of values and dividing the total by the number of values.

Mechanical pain: Mechanical pain arises from pressure or touch.

Media impression: A media impression is the interaction between a web site, radio spot, television program, or newspaper or magazine article and a single member of the audience who is exposed to that medium.

Medially: Toward the middle; closer to or oriented toward the midline or median plane of a body or structure. The "median plane" refers to the imaginary plane that divides a body into symmetrical parts.

Medication: Medication is a drug that has an effect on the body. It is usually used to treat a certain illness or condition.

Melanoma: Melanoma is the most serious life-threatening type of skin cancer. The tumor cells develop in the melanocytes, the cells that give skin its color.

Membrane: A membrane is a thin film that allows only some substances to pass through it or that prevents the mixing of two substances.

Membrane lipid peroxidation: the oxidative deterioration of polyunsaturated fatty acids in which polyunsaturated fatty acids are converted to lipid hydroperoxides.

Memory: Memory is how information is processed. It requires that a person is able to gather information. That information then has to be stored and held onto for a period of time. The final step is to recall the information when the person wants it.

Meningitis: Meningitis is an infection of the meninges, the thin three-layer membranes that cover and protect the brain and spinal cord.

MERFF syndrome (myoclonus epilepsy with ragged-red fibers): A rare hereditary disorder characterized by neurologic and muscle abnormalities due to defects of genetic material (DNA) in mitochondria, the rod-like structures outside the nuclei of cells that serve as a primary source of cellular energy. Removal and microscopic examination of minute samples of muscle fibers reveal structurally abnormal mitochondria (a finding known as "ragged-red fibers"). Associated symptoms include muscle weakness; sudden, involuntary, "shock-like" muscle contractions induced by voluntary movements or in response to external stimuli (action or reflex myoclonus); repeated seizures (epilepsy); progressively impaired coordination of voluntary movements (ataxia); and/or gradual deterioration of intellectual functioning (dementia). Some affected individuals may also have additional abnormalities, such as hearing loss; degeneration of the nerves (i.e., optic nerves) that convey impulses from the retinas to the brain (optic atrophy); short stature; heart muscle disease (cardiomyopathy); or other findings.

Metabolism: Refers to the ongoing chemical processes of cells of the body, including catabolism and anabolism. Catabolism or so-called "destructive metabolism" is the breakdown of complex chemical compounds into simpler substances, typically liberating or releasing energy. In contrast, anabolism or "constructive metabolism" refers to the "building up" or conversion of simple substances into more complex chemical compounds, requiring energy consumption (provided by catabolic processes).

Methylphenidate: Methylphenidate is a drug that is used as a central nervous system stimulant. A common trade name is Ritalin®. This drug is usually used to treat symptoms of attention-deficit/ hyperactivity disorder or narcolepsy. It acts like caffeine but has a more powerful alerting effect and is not as potent as amphetamines.

Metoclopramide: Metoclopramide is a medication used to treat nausea and vomiting or migraine and to help with emptying the stomach for people with specific medical conditions. It works by blocking dopamine receptors.

Micrographia: Micrographia is small writing. It comes from two Greek words—micro and graph—micro means small, graph means to write.

Mini-Mental State Examination : This short clinician-administered test measures cognitive status (the ability to think, calculate, and reason) in adults. This test is used to measure the presence of impaired cognition or a change in cognition over time.

Mitochondrial: Referring to mitochondria or rod-like structures inside cells of the body whose primary functions include the production and regulation of energy.

Mitochondrial dysfunction: Mitochondria are the main energy source of cells. Mitochondria convert nutrients into energy and also perform many other specialized tasks. Dysfunction means that something is not working or functioning in the correct way. Therefore, mitochondrial dysfunction refers to a situation in which the mitochondria are not working properly.

Monoamine: A molecule containing one amine group. An amine is an organic compound containing nitrogen. The so-called "biogenic monoamines" are natural, biologically active compounds that often function as neurotransmitters, including dopamine, serotonin, noradrenaline, and epinephrine.

Monotherapy: A drug used alone to treat a disease (opposite of combination therapy).

Mood or bipolar disorder: Mood or bipolar disorder is a mental illness in which people have wide mood swings. The moods include mania, during which the person has lots of energy or is excessively irritable, and depression, during which the person feels sad and hopeless. The person with bipolar can have normal moods between the swings but may also switch quickly between the highs and lows. Psychosis: Psychosis is a thought disorder characterized by impaired ability to distinguish reality from unreality, personality changes, and deterioration of normal social functioning. People with psychosis may experience hallucinations, illusions, or delusions, or they may be paranoid or have distorted thinking.

Motor fluctuations: Motor fluctuations occur when levodopa is used to treat Parkinson’s disease. As the disease becomes worse, the number of cells in the brain that store dopamine decreases, the symptoms of Parkinson’s disease worsen, and levodopa is not as effective in controlling the symptoms. When this happens, a person is said to have “off” episodes.

Motor symptoms: The motor symptoms of Parkinson's disease include tremor, stiffness (called rigidity), slowness or absence of movement (called bradykinesia or akinesia, respectively), and difficulty maintaining balance or unstable posture.

Multiple sclerosis (MS): A progressive disease of the central nervous system characterized by destruction of myelin (demyelination), the fatty substance that forms a protective sheath around certain long nerve fibers (axons). Myelin serves as an electrical insulator, enabling the effective transmission of nerve signals. Patients with MS may develop paresthesias, such as numbness or tingling; muscle weakness and stiffness; impaired coordination; abnormal reflexes; an inability to control urination (urinary incontinence); slurred speech; visual disturbances; and/or other symptoms and findings.

Multiple Sleep Latency Test (MSLT): The MSLT is used to measure how likely a person is to fall asleep. The test takes place over a seven-hour period during the day. Every two hours, for 20 minutes, the patient lies in a quiet dark room and is hooked up to a machine that measures brain waves, heart rate, muscle activity, and eye movements. This recording allows the doctor to see how quickly the patient falls asleep in this situation or if the patient falls asleep at all.

Multiple System Atrophy: A neurodegenerative disorder characterized by parkinsonism, ataxia, and dysfunction of the autonomic nervous system

Muscle tone: The low level of contraction in a muscle not being intentionally contracted.

Mutated: Altered; a mutation is a change in a gene

Mutation: A change in a gene, such as loss, gain, or substitution of genetic material, that alters its function or expression. This change is passed along with subsequent divisions of the affected cell. Gene mutations may occur randomly for unknown reasons or may be inherited.

Myelin: The whitish, fatty substance forming the segmented, multilayered wrappings or "sheaths" around certain long nerve fibers or axons. Myelin sheaths electrically insulate axons, serving to speed the transmission of nerve signals (action potentials).

Myelinated: Referring to long nerve fibers (axons) that have myelin sheaths. Consisting of segmented, multilayered wrappings of myelin, a whitish protein, myelin sheaths wrap around certain nerve fibers, providing electrical insulation and serving to speed the transmission of nerve signals.

Myoclonic: Pertaining to myoclonus or irregular, involuntary, shock-like contractions or spasms of a muscle or muscle group.

Myoclonus: A neurologic movement disorder characterized by brief, involuntary, twitching or "shock-like" contractions of a muscle or muscle group. These jerk-like movements may be accompanied by periodic, unexpected interruptions in voluntary muscle contraction, leading to lapses of sustained posture (known as "negative myoclonus"). So-called "positive" and "negative" myoclonus are often seen in the same individuals and may affect the same muscle groups. Myoclonus is often a nonspecific finding, meaning that it may occur in the setting of additional neurologic abnormalities and be associated with any number of underlying conditions or disorders. In other patients, myoclonus appears as an isolated or a primary finding. Depending on the underlying cause and other factors, the shock-like muscle jerks may occur repeatedly or infrequently; may tend to appear under specific circumstances (e.g., with voluntary movements or in response to specific external sensory stimuli); and may affect any body region or regions.

Narcolepsy: Narcolepsy is a sleep disorder marked by sudden, uncontrollable urges to sleep that cause a person to fall asleep at inappropriate times.

Nasoduodenal tube: A nasoduodenal tube is a flexible rubber tube that is inserted through the nose and into the duodenum (the section of the small intestine closest to the stomach) via the esophagus and stomach. It can be used to remove the contents of or decompress the small intestine or to provide nutrition support or medication.

Nasolaryngoscopy: Nasolaryngoscopy is a procedure done to look at the larynx, or voice box. During this procedure, the doctor inserts a laryngoscope through the patient’s nose into the throat.

National Institutes of Health (NIH): The NIH is one of the world’s foremost medical research centers and the federal focal point for medical research in the United States. The NIH, comprising 27 separate Institutes and Centers, is one of eight health agencies of the Public Health Service that, in turn, is part of the U.S. Department of Health and Human Services.

Nausea: Nausea in Greek means sea-sickness. Nausea is a feeling of discomfort in the stomach that precedes vomiting. A person does not have to vomit though in order to have nausea.

Necrosis: Cell death. Loss of cells, tissues, or parts of a structure or organ due to the progressively degrading actions of certain enzymes, such as the degradation of DNA within the nucleus of dying cells. Necrosis may result from a loss of blood supply (ischemia), infection, excessive exposure to ionizing radiation, certain chemicals, or extreme temperatures.

Neoplastic: Relating to the formation of a neoplasm (tumor) or a new, abnormal growth characterized by uncontrolled, progressive multiplication of cells. Neoplasms may be benign or malignant.

Nerve conduction velocity (NCV) test: A diagnostic study during which both sensory and motor nerves are repeatedly stimulated in order to measure the speed at which nerve impulses are conducted. Unusually slow conduction velocities suggest damage to nerve fibers (e.g., loss of the protective covering surrounding certain nerve fibers [demyelination] or other disease process).

Nervous system: The nervous system of the human body is divided into two interconnected systems: the central nervous system, which is made up of the brain and spinal cord, and the peripheral nervous system. The peripheral nervous system is further divided into the somatic nervous system (made up of peripheral nerve fibers that send sensory information to the central nervous system and motor nerve fibers that project to skeletal muscle) and the autonomic nervous system.

Neuroacanthocytosis: Also known as choreoacanthocytosis, this is a genetic disorder that most often becomes apparent between the ages of 25 to 45 years. The disorder is usually transmitted as an autosomal recessive trait. Associated symptoms may include generalized chorea; dystonia affecting muscles of the mouth and tongue; potentially mutilating lip- and tongue-biting; and sudden, involuntary, repetitive muscle movements (motor tics) and vocalizations (vocal tics). Patients may also develop personality changes and cognitive decline, seizures, parkinsonism, atrophy of muscle tissue (amyotrophy), and difficulties speaking and swallowing. Neuroimaging studies may reveal atrophy of certain regions of the basal ganglia (e.g., caudate nuclei and putamen [striatum]). The disorder may be confirmed by blood tests revealing the presence of abnormal circulating red blood cells that have spur-like or thorny projections (acanthocytosis).

Neurochemical: Referring to the chemistry or biochemical processes of the nervous system, such as activities involving naturally produced chemicals (i.e., neurotransmitters) that enable nerve cells (neurons) to communicate.

Neurodegenerative: Marked by or pertaining to neurologic degeneration; deterioration of the structure or function of tissue within the nervous system.

Neuroimaging: The production of detail, contrast, and clearness in images of the brain and spinal cord (central nervous system) through the use of computed tomography (CT) scanning, magnetic resonance imaging (MRI), positron emission tomography (PET) scanning, or other imaging techniques to assist in diagnosis, treatment decisions, or research.

Neuroleptic: a drug used to treat psychotic behavior.

Neuroleptic malignant syndrome: a life-threatening neurologic disorder most often caused by an adverse reaction to neuroleptic or antipsychotic drugs. Symptoms include high fever, sweating, unstable blood pressure, stupor, muscular rigidity, and autonomic dysfunction. In most cases, the disorder develops within the first 2 weeks of treatment with the drug; however, the disorder may develop any time during the therapy period. The syndrome can also occur in people taking anti-parkinsonism drugs known as dopaminergics if those drugs are discontinued abruptly.

Neurologic: Neurologic refers to the nervous system. The nervous system is made up of the brain, spinal cord and nerves throughout the body. It can also refer to neurology. This is the medical specialty that deals with disorders of the nervous system.

Neurologist: A neurologist is a doctor who diagnoses and treats diseases of the nervous system. The nervous system is made up of the brain, spinal cord, and all the nerves in the body.

Neuron: A neuron is a nerve cell. It is the smallest unit within the nervous system, which is made up of the brain, spinal cord, and all the nerves in the body. A neuron can send and receive information by using either electrical or chemical signals. This information is passed from one neuron to another neuron or to a body part using these signals.

Neuronal: Pertaining to a neuron or neurons.

Neuropathology: Neuropathology is the study of diseases in the nervous system. The nervous system is made up of the brain, spinal cord, and all of the nerves in the body.

Neuroprotection: Neuroprotection includes strategies to protect nerve cells from injury or degeneration.

Neuroreceptor: Specific sites on the surface of a nerve cell to which certain special substances (neurotransmitters) bind, initiating the conduction of impulses (or signals) to other nerve cells.

Neurotoxin: Neurotoxin is a substance that interferes with the electrical activity or functioning of nerve cells (neurons), preventing them from communicating with each other.

Neurotransmitter: A neurotransmitter is a chemical made in the body that allows nerve cells to communicate. It is the messenger sent from one nerve cell to another

Nigrostriatal system: Referring to the substantia nigra, the striatum, and the connection between them.

Nocardia asteroides: Nocardia asteroides are gram-positive bacteria that are found throughout the world in the soil. Localized infections usually occur in the skin following contamination of a scrape or scratch, and disseminated infections typically occur when a person with a compromised immune system inhales the bacteria. The primary site of disseminated infection is typically the lungs, where abscesses form, but the infection may spread to other parts of the body, including the brain, liver, and kidneys.

Nocturnal Sleep Dysfunction: Nocturnal means at night. Sleep dysfunction refers to basically anything that affects or interrupts sleep. Nocturnal sleep dysfunction can be caused by symptoms of PD, such as tremor or rigidity, drooling, or needing to get up to go to the bathroom at night. It can also be caused by sleep disorders such as insomnia, restless legs syndrome, rapid eye movement sleep behavior disorder, or sleep apnea.

Nomenclature: System of names used in a particular scientific discipline to consistently and methodically designate certain classifications and avoid confusion or ambiguity.

Non-ergotoline medication: A dopamine agonist medication that has action similar to that of pergolide (Permax®) and bromocriptine (Parlodel®) but is not derived from an ergot. Examples of nonergotoline medications that are used to treat some neurologic movement disorders include pramipexole (Mirapex®) and ropinirole (Requip™.)

Non-kinesigenic: Not induced by movement; provoked by factors other than sudden motions. This term often refers to abrupt episodes of involuntary movement that occur spontaneously or may be worsened by fatigue, stress, alcohol or caffeine intake, heat or cold, fasting, or other factors.

Nonmotor symptoms: Nonmotor signs and symptoms of Parkinson disease include apathy, anxiety, bladder problems, constipation, dementia, depression, fatigue, hyperhidrosis (excessive sweating), numbness, pain, psychosis, sexual dysfunction, sialorrhea (excessive drooling), and sleep disorders.

Noradrenaline (norepinephrine): A vasoconstrictor whose release triggers action within the sympathetic nervous system, the part of the nervous system that regulates certain involuntary responses during times of stress. Noradrenaline serves as a neurotransmitter that stimulates receptors (alpha- and beta-adrenergic receptors) at effector organs supplied or innervated by certain sympathetic nerve fibers (postganglionic adrenergic fibers). In addition to its production by neurons, noradrenaline is also secreted by the inner region of the adrenal glands (adrenal medulla). The release of noradrenaline serves to deepen breathing, raise blood pressure, and increase the heart rate. It also plays a role in regulating mood.

NREM sleep: Non-REM (nonrapid eye movement) sleep, which is the normal period of dreamless, lighter sleep as compared to the deeper REM sleep. NREM sleep accounts for the major portion of sleep.

Nuclear envelope: The nuclear envelope is a membrane that surrounds the nucleus in eukaryotic cells, separating the DNA in the nucleus from the rest of the cell.

Nucleic acids: Nucleic acids are molecules that carry human genetic information. The most common nucleic acids are DNA and RNA. These molecules were named nucleic because scientists first found them in the nucleus of the cell. More recently, however, scientists have also found these molecules outside the nucleus of cells.

Nucleus: The nucleus is the part of the cell that contains the genetic material; it is surrounded by the nuclear envelope.

Obsessive-compulsive behaviors: The performance of certain repetitive actions or rituals in response to persistent thoughts or impulses. For example, obsessions may consist of repeated doubts, such as wondering whether the stove was left on; a need for routine; or impulses to perform certain inappropriate actions. Compulsions frequently include repeated checking and rechecking, such as ensuring that the stove is indeed off; touching particular objects in a specific pattern or sequence; repetitive hand washing; or other repetitious behavior performed in an attempt to prevent or relieve anxiety, distress, or a feeling of dread.

Obstructive sleep apnea: A sleep disorder characterized by episodes of temporary cessation of breathing due to obstruction of the airway.

Oculomotor: Relating to or causing movement of the eyes.

Off episodes: This term refers to the times when people with Parkinson's disease have a decrease in the ability to move (hypomobility) and other symptoms that cause difficulty rising from a chair, speaking, walking, or performing their usual activities. Off episodes occur because the person's dose of levodopa has worn off too soon or has suddenly and unexpectedly stopped providing benefit.

Off time: This term refers to the times when people with Parkinson's disease have a decrease in the ability to move (hypomobility) and other symptoms that cause difficulty rising from a chair, speaking, walking, or performing their usual activities. Off episodes occur because the person's dose of levodopa has worn off too soon or has suddenly and unexpectedly stopped providing benefit.

Olivopontocerebellar atrophy (OPCA): A group of rare hereditary disorders characterized by neurodegenerative changes of certain brain regions, including the cerebellum and specialized groups of nerve cells (nuclei) in the brainstem (e.g., olivary and pontine nuclei). With most forms of the disorder, initial symptoms become apparent from adolescence to mid-adulthood; however, a rare form has been identified that may be evident at birth. Depending upon the type of OPCA, symptoms may include progressively impaired coordination, postural instability, slurred speech (dysarthria), and other associated findings (i.e., cerebellar ataxia); parkinsonism; rapid, involuntary, rhythmic eye movements (nystagmus); and/or retinal degeneration. Some affected individuals may also have additional symptoms and findings, such as involuntary, rapid, jerky movements (chorea); relatively slow, writhing motions that appear to "flow" into one another (athetosis); increased muscle stiffness (rigidity) with associated twisting or distorted posturing of affected muscles (dystonia); and/or other abnormalities. Most forms of OPCA are inherited as autosomal dominant traits; however, autosomal recessive forms have also been identified.

On time: Motor fluctuations occur when levodopa is used to treat Parkinson’s disease. As the disease becomes worse, the number of cells in the brain that store dopamine decreases, the symptoms of Parkinson’s disease worsen, and levodopa is not as effective in controlling the symptoms. When this happens, a person is said to have “off” episodes. The times in which the levodopa is effective and the person with Parkinson’s disease is able to function normally is called “on time.”

On-off phenomenon: ON-OFF phenomenon or effects refer to the unpredictable response to levodopa medication for the treatment of Parkinson disease. A sudden change can occur in a person’s ability to move around, with the person being able to move with ease (that is, ON) and then, for no apparent reason, having difficulty with movement (OFF).

Opiate: Any preparation or derivative of opium.

Opioids: Means "like or similar to opium" and refers to medications with opium-like effects. This term is used to describe any synthetic drug that possesses the characteristic properties of opiate narcotics but is not derived from opium.

Organic: An organic disease or disorder is caused by a problem with the function or structure of tissue or one or more organs of the body.

Orthostatic hypotension: Orthostatic hypotension is a particular kind of blood pressure drop. It happens when a person is lying or sitting down. When the person stands up then, the blood pressure drops a lot. This can cause dizziness or even fainting.

Otolaryngology: Otolaryngology is a medical specialty that studies and treats diseases of the ear, nose, and throat.

Oxidative stress: Oxidative stress is a process in which substances called free radicals build up in the cells as the cells convert nutrients into energy. The free radicals damage different parts of the cells in a process that is similar to the way in which rust builds up on metal. The free radicals can be counteracted by antioxidants, but if your cells do not have enough antioxidants, the free radicals accumulate and cause damage. Coenzyme Q10 acts as a scavenger of free radicals.

Palate: The bony and muscular structure that forms the roof of the mouth and separates the oral and nasal cavities.

Pallidotomy: A pallidotomy is a surgical procedure that destroys the globus pallidus, a structure in the brain. The thalamus is found deep inside the brain. Pallidotomy can be used to treat tremor and rigidity in Parkinson’s disease. It is rarely recommended anymore, and has been replaced by deep brain stimulation.

Parallel-group study: In a parallel-group study, each participant is assigned to receive a single treatment. This is opposed to a cross-over study, in which participants receive some or all of the treatments.

Paranoia: Elaborate and overly suspicious thoughts and feelings of persecution

Parasympathetic nervous system: Part of the nervous system that, together with the sympathetic nervous system, forms the autonomic nervous system (ANS). The ANS controls the functioning of involuntary structures, including the heart, glands, and smooth muscle. The parasympathetic nervous system regulates nerve transmissions to certain effector organs under normal conditions, as opposed to times of stress. It serves to "steady" involuntary activities and conserve or restore energy. Parasympathetic responses may include slowing of the heart and breathing rates, contraction of the pupils, an increase in glandular activity, and an acceleration in the rate of peristalsis.

Parathyroid glands: Two pairs of endocrine glands located in the neck at the back of the thyroid gland. The parathyroid glands produce parathyroid hormone, which increases blood calcium levels by causing bones to release calcium into the blood, the kidneys to conserve calcium, and the intestines to increase calcium absorption from food. When blood calcium levels are high, the parathyroid glands reduce their production of parathyroid hormone, essentially reversing the process.

Paresthesias: Abnormal sensations occurring spontaneously or in response to stimulation. Paresthesias may include prickling, tingling, burning, or tickling feelings; numbness; "pins and needles"; or cramp-like sensations. Various neurologic movement disorders may be characterized by paresthesias, including restless legs syndrome (RLS), paroxysmal kinesigenic dyskinesia (PKD), and paroxysmal non-kinesigenic dyskinesia (PNKD).

Parkinson's disease (PD): A slowly progressive degenerative disorder of the central nervous system characterized by slowness or poverty of movement (bradykinesia), rigidity, postural instability, and tremor primarily while at rest. Additional characteristic findings include a shuffling, unbalanced manner of walking; forward bending or flexion of the trunk; a fixed or "mask-like" facial expression; weakness of the voice; abnormally small, cramped handwriting (micrographia); depression; or other symptoms and findings. Such abnormalities are thought to result from progressive loss of nerve cells within a certain region of the substantia nigra of the brain and the associated depletion of the neurotransmitter dopamine.

Parkinsonism: Parkinsonism is a term that refers to a group of symptoms: tremor, rigidity, bradykinesia, and postural instability. These are usually seen in Parkinson’s disease, but there are other diseases that cause parkinsonism. Certain drugs can also cause this, and are usually reversible once the drug is stopped.

Paroxysmal: Pertaining to or occurring in paroxysms or sudden, recurrent episodes. The term paroxysms often describes transient episodes of abnormal involuntary movements (e.g., chorea, athetosis, dystonia, and/or ballismus) or ataxia, which is characterized by an impaired ability to coordinate voluntary movements.

Paroxysmal movement disorders: Certain neurologic movement disorders characterized by abrupt, transient episodes of abnormal involuntary movement, such as chorea, athetosis, dystonia, and/or ballismus (i.e., the paroxysmal dyskinesias) or impaired coordination of voluntary actions and other associated findings (i.e., paroxysmal ataxias). Depending upon the specific disorder present, episodes may be precipitated or worsened by different factors. As examples, in those with paroxysmal kinesigenic dyskinesia (PKD), episodes may be triggered by sudden voluntary movements. In non-kinesigenic dyskinesia (PNKD), episodes occur spontaneously and may be worsened by caffeine or alcohol consumption, stress, fatigue, or other factors. In patients with paroxysmal kinesigenic ataxias, episodes may be triggered by sudden voluntary movements or postural changes. These disorders may be familial, appear to occur randomly for unknown reasons (sporadically), or occur secondary to other underlying conditions or disorders (symptomatic).

Pathogenesis: the origination and development of a disease.

Pathophysiology: The effects of disease on body functions; the physiology of altered function seen in disease. ("Patho-" is a combining form denoting any disease state, and "physiology" refers to the study of the processes and functioning of the human body.)

Patient registry: A patient registry is a list of people who have a specific disease. This list allows researchers and doctors to contact people who have an illness or disease to see if they want to participate in clinical studies. The information on a patient registry is not available to anyone other than the researchers, and patient privacy is always protected.

Penetrance: The regularity or frequency with which a specific gene yields its effect or "is expressed." For example, if a specific gene produces a disease in all individuals who carry the gene, it is termed 100% penetrant. If a gene produces the disease less than 100% of the time, it is not fully penetrant.

Peptide: Peptides are short chains of amino acids.

Pericardium: The pericardium is the two-layered sac that surrounds and protect the heart. If the pericardium becomes fibrotic or filled with fluid, it limits the motion of the heart and, therefore, the ability of the heart to pump efficiently.

Periodic apnea: Episodes of the temporary cessation of spontaneous breathing. Periodic apnea may be characterized by absence of airflow, absence of chest wall movements, or airway obstruction that may result from poor control of tongue movements, impaired coordination of upper airway muscles, or other abnormalities.

Periodic limb movements in sleep (PLMS): Periodic limb movements of sleep are regular rhythmic twitches of the limbs that occur during sleep. The twitches usually affect the legs but they also sometimes affect the arms. The twitches usually last between half a second and five seconds and usually occur every five to 90 seconds. The diagnosis of periodic limb movement disorder is based on the results of an overnight sleep study. If the person has five or more series of limb movements per hour of sleep, a diagnosis of periodic limb movement disorder is made.

Perioperative setting: The perioperative setting is the time before, during, and after an operation.

Peripheral edema: unusual fluid accumulation, resulting in swelling of the arms or legs.

Peripheral nervous system: The peripheral nervous system is that portion of the nervious system outside of the brain and spinal cord (central nervous system)

Peripheral neuropathy: Inflammation, degeneration, or damage of nerves of the peripheral nervous system (PNS). The PNS includes nerves that extend from the brain and spinal cord (central nervous system) to various parts of the body. Peripheral neuropathy may involve motor nerves, causing muscle weakness, and/or sensory nerves, resulting in pain, abnormal sensations, such as numbness or tingling, or other findings.

Peristalsis: Rhythmic, wave-like contractions of smooth or involuntary muscle fibers that propel food through the digestive tract.

Phenomenology: classification based on a scientific explanation.

Phenylalanine: an essential amino acid that is converted in the body to tyrosine.

Phenylketonuria: an inherited disorder that, if untreated, causes profound mental retardation as well as other medical problems.

Phonation: The production of speech; utterance of sounds through use of the vocal cords.

Physiatrist: a physician specializing in physical medicine and rehabilitation.

Physiologic tremor: A form of rapid tremor that may occasionally occur in any individual. Physiologic tremor is typically the result of fear, anxiety, or excitement. Physiologic tremor may affect the arms, legs, and, in some patients, the face or neck.

Pill-rolling tremor: To understand what a pill-rolling tremor looks like, imagine a person holding a pill between her first finger and thumb. You can get an idea by extending your first finger and your thumb and holding them together at the first joint of each. Slide the finger away from your hand and your thumb toward your hand—in opposition. Now reverse the movement, sliding your finger toward your hand and your thumb away from your hand. Slowly repeat these movements and you will have an idea of what the pill-rolling tremor looks like. People with Parkinson disease have this type of tremor when their hands are at rest. At first, it may affect only one hand, but over time, it may affect both hands or may alternate, at times affecting one and then the other hand.

Pittsburgh Sleep Quality Index: This 24-item self-administered questionnaire is designed to provide a brief clinically useful assessment of a variety of sleep disturbances that might affect sleep quality.

Placebo: A placebo is a substance that appears to be identical to the treatment under study but that has no effects on the test subject. The placebo is given to members of the control group during experimental trials that test the effects of a drug or other substance.

Placebo-controlled trial: A placebo-controlled trial is a clinical experiment in which patients have been randomly assigned to receive either the treatment under study or placebo, an alternative that has no effects.

Pleura: The pleura are the two-layer membranes that cover the outside of the lungs and line the chest cavity.

Polymerase chain reaction (PCR): A highly sophisticated technique during which a known sequence of DNA is copied rapidly over a short period, such as millions of copies over a few hours. PCR testing assists in diagnosing certain genetic disorders, helps identify individuals through analysis of a single cell or so-called "DNA fingerprinting," or characterizes certain strains of infectious microorganisms.

Positron emission tomography (PET): An advanced, computerized imaging technique that uses radioactively-labels substances (e.g., glucose) to demonstrate chemical and metabolic activities in the brain as well as track other brain functions. Brain structures are also visualized on PET scans.

Positron emission tomography (PET) scanning: A noninvasive, diagnostic procedure used to record the uptake and distribution of certain substances in the tissues and organs of the body. Thus, PET assists in evaluating various metabolic and physiological activities in the body. During this procedure, three-dimensional, color-coded images are created based upon the detection of positively charged particles (positrons). The positrons are produced by certain biochemicals (e.g., glucose) carrying radioactive substances that have been introduced into the body (via intravenous injection). PET scanning may help to detect abnormal biochemical patterns associated with certain neurologic conditions, such as Parkinson’s disease, brain tumors, seizure disorders, and psychiatric abnormalities.

Postural instability: Postural instability is a difficulty with balance.

Postural tremor: Any tremor that is present while an individual voluntarily maintains a position against gravity, such as holding the arms outstretched.

Precursor: Literally a "forerunner," such as a substance that precedes another in a biochemical reaction.

Prenatally: Before birth.

Prevalence: Prevalence refers to the number of people in a given group or population who have a disease.

Probe: A genetic probe is a single strand of DNA or RNA with a specific base sequence used to detect the corresponding base sequence by hybridization—which is the process of joining two complementary strands of DNA or one each of DNA and RNA to form a double-stranded molecule. The single strand is either radioactively or immunologically labeled.

Progressive supranuclear palsy (PSP): A progressive neurological disorder characterized by neurodegenerative changes of certain brain regions, including particular areas of the basal ganglia and the brainstem. Symptom onset most often occurs in the sixth decade of life. Associated findings may include balance difficulties, sudden falls, stiffness (rigidity), slowness of movement (bradykinesia), an impaired ability to perform certain voluntary eye movements, and visual disturbances. Affected individuals may also develop slurred speech; swallowing difficulties; personality changes; dystonia; sudden, involuntary, "shock-like" muscle contractions (myoclonus); or other abnormalities. The disorder usually appears to occur randomly for unknown reasons (sporadically); however, there are some reports of families with multiple affected members, suggesting a possible hereditary component to the disease.

Prophylactic: Referring to preventive treatment (i.e., prophylaxis); a medication, procedure, or device that serves as a preventive against disease.

Prophylaxis: Protection from or the prevention of disease; preventive (i.e., prophylactic) therapy; often refers to the use of a drug, mechanical agent, or procedure to prevent infection with certain microorganisms (e.g. bacteria).

Proteasome inhibitor: A proteasome inhibitor is a chemical that interferes with, or inhibits, the action of proteasomes—the recyclers of proteins in the cells.

Protein: Proteins are large complex molecules made up of amino acids. Each protein starts out as a chain of amino acids. Determined by the sequence of the base pairs in the gene that encodes it, the protein then folds itself into its unique shape. Proteins serve many different roles within the body, including providing structure (collagen), allowing movement (actin and myosin), increasing the rate of a chemical reaction (enzymes), transporting substances (hemoglobin); regulating processes within the cells (insulin); and responding to the stimuli (receptor proteins on surface of all cells).

Proxy: A proxy is someone who is authorized to act on behalf of another person. This person may be a relative or friend, for example.

Psychogenic: A psychogenic disorder has a mental or emotional origin. Psychogenic also refers to a symptom, condition, or disorder that is caused by mental, psychological, or emotional factors rather than physical illness.

Psychosis: Psychosis is a thought disorder characterized by impaired ability to distinguish reality from unreality, personality changes, and deterioration of normal social functioning. People with psychosis may experience hallucinations, illusions, or delusions, or they may be paranoid or have distorted thinking.

Pulmonary: Referring to the lungs.

Pulmonary fibrosis: Pulmonary fibrosis is a condition in which excessive scar tissue forms in the lungs, making them stiff, decreasing the amount of surface area that is available to provide gas exchange, and interfering with their function.

Putamen: One of the 3 major brain regions that, together with the caudate nuclei and the globus pallidus, comprise the basal ganglia. Relatively similar in function and structure, the putamen and the caudate nuclei are collectively referred to as the striatum. Specialized groups of nerve cells within the putamen receive input from various regions of the cerebral cortex. The messages are processed and relayed by way of the thalamus to the motor cortex, influencing voluntary movement.

Randomized controlled : In a randomized controlled trial or study, participants are randomly assigned to different treatments or conditions to study the effectiveness of the treatment or condition.

Range of motion (ROM): The extent of a joint's free movement. The normal ROM of the elbow, for instance, carries the forearm through a half-circle. Passive ROM is tested while the limb is relaxed. Active ROM is movement controlled by the patient.

Receptor: A receptor is one end of the nerve cell that receives messages from other nerve cells. These messages are usually neurotransmitters sent by other nerve cells. Drugs, however, can affect receptors directly without using neurotransmitters.

Reduced penetrance: Reduced expression of a genetic disorder. The term penetrance refers to the frequency with which a specific genetic mutation produces its typical effect in those with the genetic abnormality. For example, if fewer than 100 percent of individuals who inherit a gene mutation for an autosomal dominant disorder develop the disease, the specific trait is said to have "reduced penetrance."

Reflex: Involuntary, predictable response to a particular stimulus.

Refractory: Resistant to or not readily yielding to treatment.

Regurgitation: In reference to the heart, regurgitation is the backward flow of blood through a defective valve.

REM sleep: Rapid Eye Movement (REM) sleep is one part of a sleep cycle. The eyes move around quickly, hence the name. This is the phase where dreaming occurs. During this phase, the body is paralyzed so that a person does not act out his dreams. Adults spend about 20% of their time in this phase.

REM sleep behavior disorder (RBD): During REM sleep, a person is normally paralyzed while dreaming. In RBD, a person is not paralyzed so he acts out his dreams. This can put the person or bed partner in danger of injury.

Restless legs syndrome (RLS): A neurologic movement disorder characterized by unusual, uncomfortable sensations (paresthesias/dysesthesias) deep within the calves and/or thighs, resulting in an irresistible urge to move the legs, and motor restlessness in response to or in an effort to alleviate discomfort. In some patients, the arms may also be affected. Symptoms become obvious or worse during periods of relaxation or inactivity; occur most frequently during the evening or the early part of the night; and may be temporarily relieved by voluntary movements of the affected area. Most patients experience associated sleep disturbances, including difficulties drifting off to and remaining asleep. RLS is also often associated with periodic limb movements of sleep (PLMS) or repeated, stereotypic, upward extension of the great toe and foot, potentially followed by flexion of the knee, hip, or ankle. Episodes of PLMS typically occur during periods of lighter (i.e., non-REM) sleep.

Restorative sleep: A refreshing sleep, i.e., receiving a sufficient amount of rest to feel refreshed and to engage in the activities of daily living without experiencing excessive daytime sleepiness (EDS).

Retina: The nerve-rich membrane that forms the innermost region of the eye. As light passes through other areas of the eye (including the cornea, pupil, and lens), it is bent or refracted to focus on the retina, which contains nerve cells that respond to light (photoreceptors). Images formed on the retina are converted into nerve impulses that are transmitted to the brain via the optic nerve (second cranial nerve).

Retinal: Referring to the retina, which is the nerve-rich membrane forming the innermost region of the eye. As light passes through the eye, it is bent (refracted) to focus on the retina, which contains photoreceptors or specialized nerve cells that respond to light. Images formed on the retina are converted into nerve impulses, which are then transmitted to the brain by the optic nerve (also known as the second cranial nerve).

Retrocollis: spasmodic torticollis in which the head is drawn directly backward.

Retroperitoneum: The retroperitoneal area is the area behind peritoneum, the covering of the intestines. The kidneys and the adrenal glands lie in the retroperitoneal area.

Reye syndrome: A potentially life-threatening disease characterized by sudden inflammation and swelling of the brain (acute encephalopathy) and rapid fat accumulation within certain internal organs (viscera), particularly the liver, occurring subsequent to certain viral infections, such as chickenpox or upper respiratory tract infections (e.g., influenza B). Reye syndrome primarily occurs in children and adolescents, although it has sometimes been reported during infancy or young adulthood. About a week after the onset of a viral infection, patients may develop uncontrollable vomiting, followed by a rapid onset of listlessness, confusion, and memory loss, a state of unconsciousness (coma), seizures, and/or other findings, potentially leading to life-threatening complications. Evidence suggests that the use of aspirin-containing preparations (salicylates) as a treatment for particular viral infections plays a role in the development of Reye syndrome. Therefore, experts advise that such medications be avoided for the treatment of viral infections during infancy, childhood, adolescence, and young adulthood.

Rhythmical myoclonus: Involuntary, shock-like contractions or spasms of a muscle or muscle group that occur in a rhythmical pattern. This usually occurs as a result of a lesion in the central nervous system.

Ribonucleic acid (RNA): RNA is a chemical that is found in the nucleus and cytoplasm of cells; it plays an important role in protein synthesis and other chemical activities of the cell.

Ribosomes: Ribosomes are small structures within a cell that are the site of protein synthesis.

Rigidity: Rigidity is stiffness or resistance to movement. It is one of several motor symptoms in Parkinson’s disease.

Rush Hallucination Inventory: This standardized clinician-administered questionnaire assesses the presence or absence of false visual (see), auditory (hear), tactile (touch), or gustatory (taste) experiences in the setting of a clear sensorium.

Sandhoff's disease: A neurodegenerative metabolic disorder that is characterized by symptoms and findings similar to those associated with Tay-Sachs disease as well as possible, moderate enlargement of the liver and spleen (hepatosplenomegaly). Sandhoff's disease is a lysosomal storage disease in which deficiency of the enzymes hexosaminidase A and B results in an abnormal accumulation of certain fats (i.e., gangliosides) in particular tissues of the body. The disorder is transmitted as an autosomal recessive trait and affects only non-Jewish individuals (as opposed to Tay-Sachs disease, which primarily occurs in individuals of Ashkenazi Jewish ancestry).

Schizophrenia: a psychiatric disorder characterized by hallucinations, delusions, disordered thinking, unusual speech or behavior and social withdrawal that impair the affected person’s ability to interact with others.

Scoliosis: Lateral or "sideways" curvature of the normally vertical line of the spine. Progressive spinal deformity may be associated with numerous neuromuscular and neurodevelopmental disorders (neurogenic scoliosis), such as cerebral palsy, spinal muscular atrophy, and Rett syndrome. The severity of the deformity varies, depending upon the degree of weakness, the nature and progression of the underlying disorder, or other factors.

Seborrhea: Seborrhea is an increased amount of the oily substance that is produced in the sweat glands of the skin. It causes the skin to glisten or appear shiny.

Sedation: An induced state of quiet or sleep

Seizures: Episodes of uncontrolled electrical activity in the brain. These abnormal electrical disturbances may lead to involuntary jerking, spasms, or rhythmic contraction and relaxation of certain muscle groups and impaired control of involuntary functions such as breathing or bladder or bowel control. There may also be loss of consciousness or sensory or behavioral abnormalities.

Sensorimotor: Pertaining to both the sensory and motor aspects of a bodily function.

Sequelae: Plural of sequela, which is any abnormal condition that occurs subsequent to and/or is caused by disease, injury, or treatment.

Sequence: As a noun, a sequence is a series of chemical bases—adenine (A), thymine (T), cytosine (C) and guanine (G)—in DNA or a string of amino acids in a protein. As a verb, sequence refers to the process of determining the order of the bases or amino acids.

Serotonin (3-[2-aminoethyl]-5-indolol): A vasoconstrictor found in many tissues of the body that is present in relatively high concentrations in portions of the central nervous system (e.g., hypothalamus, basal ganglia, etc.). Serotonin functions as a neurotransmitter, regulating the delivery of messages between nerve cells (neurons). This neurotransmitter is thought to play some role in regulating consciousness and mood states. Serotonin is also present in other tissues of the body such as the intestines and blood platelets.

Sexual dysfunction: Sexual dysfunction is any problem with sexual activity. It could be a problem with desire, arousal, or orgasm. In men, it usually means having problems with erections.

Sialidosis: A lysosomal storage disease in which deficiency of the enzyme neuraminidase leads to abnormal accumulation of certain complex carbohydrates (sialyloligosaccharides) in particular tissues and organs. There are different variants of the disorder, based upon age of onset, severity, and other factors. Sialidosis type I, also known as "cherry-red-spot myoclonus syndrome," usually becomes apparent during the second decade of life. Associated symptoms include the development of characteristic, cherry-red circular areas within the middle layers of the eyes; gradual loss of visual clarity; and sudden, involuntary, "shock-like" contractions (myoclonus) of muscles of the arms and legs. The myoclonus is progressive in nature and may be triggered by voluntary movements (action myoclonus) or certain external stimuli, such as sound (reflex myoclonus). Sialidosis is inherited as an autosomal recessive trait.

Sialorrhea: Sialorrhea means having too much saliva. It causes a person to drool. It could be because a person makes too much saliva. It could also be because a person has problems swallowing, and the saliva stays in the mouth.

Side effect: An effect of a drug that is not the main or intended effect. Side effects may be of no concern, or they may be bothersome or even dangerous, in which case they may limit the upper dose a patient can tolerate. Side effects are also called adverse effects.

Single photon emission computed tomography (SPECT): SPECT is a noninvasive scanning procedure during which a radioactive substance known as a radionuclide is introduced into the body to help evaluate the function and structure of certain organs or tissues. The amount of the substance taken up by particular tissues may depend upon the amount of blood flow within such regions. For example, absence of radionuclide uptake in a targeted region may indicate a lack of blood flow in certain areas. Following intravenous administration of the radioactive compound, a specialized rotating camera detects the radiation emanating from the radionuclides in the form of particles known as protons. The recorded images may produce colorized, horizontal and vertical cross-sections and may be reconstructed by computer to create three-dimensional images. By evaluating the blood supply to particular tissues, SPECT may be particularly helpful in detecting certain changes within the brain, spinal cord, or heart.

Sinus bradycardia: an abnormally slow heart rate (i.e., of less than 60 beats per minute).

Sleep fragmentation: Sleep fragmentation is a continual disruption of sleep, which often leads to excessive daytime sleepiness. This disruption can occur as the result of a variety of factors, including sleep disorders, the need to get up to use the bathroom, pain, and a noisy or uncomfortable sleeping environment.

Sleep latency: The interval of time between "settling in" to go to sleep and the onset of sleep.

Sleep maintenance: Once asleep, the ability to remain asleep.

Sleep paralysis: Sleep paralysis is a total inability to move that occurs while the person is falling asleep or immediately upon awakening.

Sodium Oxybate: Sodium oxybate is also known as gamma hydroxybutyrate or GHB. This clear odorless liquid was approved by the US Food and Drug Administration in 2002 for the small number of people who have narcolepsy with cataplexy. Because of the high potential for abuse and misuse, the drug is only available from a single central pharmacy and its distribution is tightly controlled.

Somatization disorder: A person with a somatization disorder has symptoms that mimic or look like those of a disease or injury but for which there is no physical cause. Although somatization disorders are likely caused by a psychological factor, they are not the result of the person deliberately producing or exaggerating symptoms.

Spasm: A spasm is an uncontrollable sudden tightening of a muscle or group of muscles.

Spasmodic dysphonia (SD): A manifestation of dystonia. SD involves the muscles of the larynx and surrounding muscles and therefore involves speech. In individuals with SD, speech in blocked by intermittent spasms of the voice box (larynx).

Spasmodic torticollis (ST): A form of dystonia involving the muscles of the neck, and therefore called "cervical dystonia." As a result of the abnormal involuntary contractions of the neck muscles, the head may be rotated, tilted, flexed, extended, or any combination of these postures. The movements may be quick, sustained, or patterned and, therefore, may be associated with tremor.

Spasmolytic: Antispasmodic; referring to agents that may eliminate or relieve spasms, typically of involuntary (i.e., smooth) muscle, such as within the arteries, the intestine, the ring-shaped muscles around certain natural openings or passages (sphincters), the bladder, the muscular tubes that carry urine from the kidneys to the bladder (ureters), etc.

Spasticity: An abnormal increase in muscle tone that may be caused by certain types of damage to the nerve pathways regulating muscles. Spasticity is a common complication of cerebral palsy, brain injuries, spinal cord injuries, multiple sclerosis, and stroke. Spasticity can lead to incoordination, loss of function, pain, and permanent muscle shortening, or contracture.

Speech pathologist: A speech pathologist is a person who diagnoses and treats problems with speech and language. This could be a problem with the voice, swallowing, or communication.

Speech therapist: A speech therapist is a professionally trained person. The speech therapist helps people with speech, language, communication, and swallowing problems.

Spinal cord: The cylindrical structure of nerve tissue that, together with the brain, comprises the central nervous system. The spinal cord is an extension of the medulla oblongata--which is part of the lowest region of the brain (brainstem)--and is contained within a central canal in the spinal column. The spinal cord and the brain are surrounded by a protective, 3-layered membrane (meninges). Cerebrospinal fluid (CSF) flows through the cavities (ventricles) of the brain, the spinal cord's central canal, and the space between the middle and inner layers of the meninges (subarachnoid space). The spinal cord consists of an inner core of gray matter and surrounding areas of white matter, composed of bundles of myelinated nerve fibers (axons) known as spinal tracts. These include ascending tracts that carry sensory impulses up the spinal cord to the brain and descending tracts that transmit motor impulses from the brain down the spinal cord. Nerves emerge from both sides of the spinal cord (i.e., spinal nerves) through the narrow gaps (foramina) between bones of the spinal column (vertebrae). The spinal nerves, which are attached to the spinal cord by specialized nerve bundles (spinal nerve roots), contain both motor and sensory neurons.

Spinocerebellar ataxias (SCA): This group of disorders, of which there are now 17 genetically identified types, are inherited as an autosomal dominant genetic trait and appear to be mostly due to increased numbers of repeats in the various genes involved (as in HD). All types of SCA involve degeneration of the cerebellum, causing impaired balance, walking, and coordination. Each type of SCA has its own typical pattern of symptoms; however, these may vary greatly from person to person. Some forms of SCA affect eye movements, swallowing, thinking, reflexes, or cause parkinsonism, chorea, or dystonia. In most types of SCA, the onset of symptoms occurs during adulthood; symptoms slowly become worse over the years.

Sporadically: Occurring intermittently, randomly, or in isolation.

SSRIs: Selective serotonin reuptake inhibitors. Drugs belonging to this class are antidepressant agents that selectively inhibit the absorption of serotonin at certain nerve membranes (e.g., presynaptic neuronal membranes). These drugs increase the concentration of serotonin within the central nervous system and enhance serotonin's neurotransmission activities.

Statistician: A statistician is a mathematician who studies data, analyzes it, and interprets it. This allows people to make sense of information collected.

Stereotactic: refers to use of precise coordinates to identify deep structures of the brain. The coordinates may be obtained by fitting a patient's head with a special frame and taking a CT or MRI scan. The position of the brain structures relative to the frame permits fine localization of the deep brain structures. Stereotactic methods are used during brain surgery for tremor, Parkinson's disease, and dystonia. These brain structures are located with precise, three-dimensional coordinates.

Stereotypic: Inappropriate, persistent repetition of particular bodily postures, actions, or speech patterns. These are typically involuntary, rhythmic, coordinated, and purposeless movements, postures, or vocalizations that may appear ritualistic or purposeful in nature. Stereotypies may be associated with a variety of neurologic and behavioral disorders, such as Tourette syndrome, obsessive-compulsive disorders, Rett syndrome, restless legs syndrome, schizophrenia, and autism.

Stereotypical: Conforming to a repetitive pattern as in repetition of particular movements or gestures.

Stimulus: A stimulus is something that creates a response in a muscle, nerve, gland or other excitable tissue or organ of the body. The plural is stimuli.

Stretch reflex: Contraction of a muscle stimulated by rapid stretching.

Stretch-loop circuits: Pathways of electrical impulses along specific nerve fibers (alpha motoneurons) that result in a "stretch" reflex in a muscle.

Striatum: An area of the brain that controls movement and balance. It is connected to and receives signals from the substantia nigra.

Study group: A study group can also be called a working group. The members of the study group meet regularly to discuss a specific topic--in this case, spasmodic dysphonia. They also work together to design research studies.

Substantia nigra: A dark band of gray matter deep within the brain where cells manufacture the neurotransmitter dopamine for movement control. Degeneration of cells in this region may lead to a neurologic movement disorder such as Parkinson's disease.

Substrate: A chemical substance that is acted upon by an enzyme is called a substrate.

Subthalamic nucleus: The subthalamic nucleus is an oval mass of gray matter located beneath the thalamus.

Sydenham's chorea: A usually self-limited condition in which chorea develops in association with an inflammatory disease caused by certain strains of streptococci bacteria. This disease, known as rheumatic fever, is characterized by the sudden onset of fever and joint pain, with subsequent inflammation of the heart (carditis), chest pain, skin rash, and other symptoms. If rheumatic fever involves the nervous system, Sydenham’s chorea may develop. This condition commonly affects children aged 5 to 15 or women during pregnancy. Sydenham's chorea involves involuntary, uncontrollable, jerky movements that gradually worsen in severity, potentially affecting arm movements, the manner of walking (gait), and speech. In most patients, the condition spontaneously resolves in weeks or months.

Sympathetic nervous system: Part of the nervous system that along with the parasympathetic nervous system forms the autonomic nervous system (ANS). The ANS regulates the functioning of involuntary structures, such as the glands, smooth muscle, and heart. The sympathetic nervous system regulates certain involuntary responses during times of strong emotion, such as fear or anger; exercise; or other forms of stress. These responses, sometimes referred to as the "fright-or-flight response," include widening of the pupils; increased heart and breathing rates; constriction of most blood vessels, raising blood pressure; widening of those blood vessels that supply skeletal muscles; and reduction in the rate of peristalsis.

Synapse: The junction between two neurons or between a neuron and an effector organ. As a nerve impulse reaches a synapse, the terminal or end of the "presynaptic" neuron's axon releases neurotransmitters, which diffuse across the gap and bind to receptors of the "postsynaptic" neuron or the effector organ (i.e., muscle or gland). As the electrical impulse is conducted across the gap, electrical changes are triggered that serve to continue or hinder transmission of the impulse.

Synthesis: The formation of a complex chemical compound through the union of simpler substances.

Systemic lupus erythematosus: an autoimmune disease involving multiple organ systems that is defined clinically and associated with antibodies directed against cell nuclei.

Tardive dyskinesia: A movement disorder that may result from extended therapy with certain antipsychotic medications such as haloperidol. The condition is characterized by involuntary, rhythmic movements of the face, jaw, mouth, and tongue, such as lip pursing, chewing movements, or protrusion of the tongue. Facial movements are sometimes accompanied by involuntary, jerky or writhing motions (choreoathetoid movements) of the trunk, arms, and legs. In some patients, symptoms discontinue months or years after withdrawal of antipsychotic therapy. However, in others, the condition may not be reversible.

Tardive dystonia: A form of tardive dyskinesia characterized by chronic dystonia due to administration of medications that block dopamine D2 receptors (dopamine receptor antagonists), such as certain antipsychotic agents. (Dopamine receptors are molecules on the surfaces of receiving nerve cells that are sensitive to stimulation by dopamine, a neurotransmitter that controls movement and balance. Several types of dopamine receptors have been identified, including D1, D2, and D3.) Dystonia is a neurologic movement disorder characterized by sustained muscle contractions that often result in repetitive twisting motions or unusual postures or positions. Tardive dystonia is the most common form of secondary dystonia--i.e., dystonia that results from certain environmental factors or "insults" that affect the brain. In adults, tardive dystonia often initially affects facial or neck muscles. Dystonia may remain limited to such regions or extend to affect adjacent muscles of the trunk and arms. Children are more likely to be affected by generalized dystonia that involves muscles of the trunk and legs.

Tauopathy: Tauopathy refers to any group of diseases that cause dementia related to a problem with tau, a protein that is important in maintaining the structure of brain cells.

Tay-Sachs disease: A progressive neurodegenerative metabolic disorder that belongs to a group of diseases called lysosomal storage diseases. Also known as GM2 gangliosidosis type I or infantile type, Tay-Sachs disease results from deficiency of the enzyme hexosaminidase A, which leads to an abnormal accumulation of certain fats (i.e., gangliosides) in particular tissues, particularly nerve cells of the brain. An autosomal recessive disorder, Tay-Sachs disease primarily affects individuals of northeastern European Jewish (Ashkenazi Jewish) ancestry. Symptom onset typically begins from about 3 to 6 months of age. Associated symptoms may include an exaggerated startle response, increasing listlessness, loss of previously acquired skills (psychomotor regression), severely diminished muscle tone (hypotonia), and the development of characteristic, cherry-red circular areas within the middle layers of the eyes (Tay's sign). With disease progression, affected infants and children may develop increasing muscle stiffness or rigidity; seizures; sudden, involuntary, "shock-like" contractions of multiple muscle groups in response to certain stimuli (generalized, stimuli-sensitive myoclonus); enlargement of the brain (metabolic megalencephaly); deafness; blindness; and dementia. Life-threatening complications may develop between 2 to 5 years of age.

Tendon: A tough fibrous cord of tissue that attaches muscle to bone (or other structures of the body).

Teratogenic: Possessing the ability to disrupt normal fetal development and causing fetal abnormalities.

Thalamotomy: A thalamotomy is a surgical procedure that destroys the thalamus, a structure in the brain. The thalamus is found deep inside the brain. Thalamotomy can be used to treat tremor and rigidity in Parkinson’s disease. It is rarely recommended anymore, and has been replaced by deep brain stimulation.

Thalamus: An area of the brain consisting of 2 relatively large masses of gray matter. The thalamus relays information from most sensory organs to the outer region of the cerebrum or cerebral cortex; receives and processes messages from the body concerning heat, cold, pain, pressure, and touch; and influences motor activity of the cerebral cortex.

Threshold: A pain threshold is the point at which a feeling or sensation becomes painful.

Tics: Involuntary, compulsive, stereotypic muscle movements or vocalizations that abruptly interrupt normal motor activities. These repetitive, purposeless motions (motor tics) or utterances (vocal tics) may be simple or complex in nature; may be temporarily suppressed; and are often preceded by a "foreboding" sensation or urge that is temporarily relieved following their execution. Simple tics include abrupt, isolated movements, such as repeated facial twitching, blinking, or shoulder shrugging, and simple sounds, including grunting, throat clearing, or sighing. Complex tics may involve more sustained, complex movements, such as deep knee bending or leg kicking, or complex vocalizations, including repeating another person's words or phrases (echolalia) or, rarely, explosive cursing (coprolalia). Tourette syndrome is defined as the presence of multiple motor and vocal tics for at least one year, changes in the nature of the tics (e.g., complexity, severity, anatomical location) during the course of the disorder, and symptom onset before age 21.

Tone: Resistance or tension in a muscle when a limb or other body part is moved passively and in a relaxed state about a joint. A state of muscle tension balanced by partial contraction or alternate contraction and relaxation.

TorsinA: TorsinA is a protein that, when defective, may cause DYT-1 dystonia. Although its exact function is not known, TorsinA is believed to be related to a series of compounds that enable cells to recover from stress and injury.

Total Functional Capacity: The Total Functional Capacity Scale is a tool that clinicians use to assess the function of people with Huntington disease. The scale includes five domains: workplace, finances, domestic chores, activities of daily living, and the need for skilled or unskilled care.

Toxic metabolites: Potentially harmful substances formed as the result of normal body functions.

Toxin: A toxin is a poisonous substance that is produced by a plant or animal

Transdermal: Transdermal means, literally, through the skin.

Transient: Temporary; transitory; not lasting or enduring.

Tremor: A tremor is a rhythmic motion involving a specific part of the body--the hands, arms, neck, head, vocal cords, trunk or legs. The motion involves the muscles going back and forth, like a rocking chair. A person with a tremor cannot control it.

Tropical spastic paraparesis (HTLV-1-associated myelopathy): A rare disorder characterized by slowly progressive weakness (paraparesis), stiffness (rigidity), and spasticity of the leg muscles due to infection with the human T-cell lymphotropic virus-1 (HTLV-1). Modes of transmission include sexual contact, mother-to-child transmission (e.g., via breastfeeding), and blood transfusion.

Tryptophan: an essential amino acid.

Tyrosine: an aromatic nonessential amino acid that is a metabolic precursor of thyroxine, the pigment melanin, and other biologically important compounds.

Unified Parkinson Disease Rating Scale (UPDRS): The UPDRS is the most commonly used to tool to rate the symptoms of Parkinson disease. This scale is intended to be used to follow the course of Parkinson disease in patients over a period of time. It is made up of four parts: (1) mentation (the process of thinking), behavior, and mood; (2) activities of daily living; (3) motor symptoms, and (4) complications of therapy.

Unilateral: Affecting, pertaining to, or confined to one side only.

Unverricht-Lundborg's disease (Baltic myoclonic epilepsy): A form of progressive myoclonic encephalopathy (PME) characterized by the development of repeated seizures or episodes of uncontrolled electrical activity of the brain (epilepsy); sudden, "shock-like" muscle contractions that may be induced by voluntary movements or in response to certain external stimuli (action or reflex myoclonus); and eventual impairment of coordination, postural instability, and other associated findings (i.e., cerebellar ataxia). Although mental deterioration may also be associated with the disorder, it is typically milder than that seen with Lafora's disease (another form of PME). Unverricht-Lundborg's disease is thought to be inherited as an autosomal recessive trait. Symptom onset typically begins from about age 6 to 13. The disorder is slowly progressive; however, the degree of disease progression and disability may be extremely variable among affected family members.

Upper motor neurons: Nerve cells extending from the brain to the spinal cord that control movement.

Vaginosis: Bacterial vaginosis involves the abnormal increased growth of certain bacteria in the vagina.

Valine: an essential amino acid.

Variable expressivity: Varying manifestation of a genetic trait. The term "expressivity" refers to the degree to which a hereditary trait appears in an individual. Thus, in individuals with a gene mutation for an autosomal dominant disorder that has variable expressivity, the specific characteristics that are manifested may vary in range and degree from mild to severe.

Vascular: Pertaining to or containing blood vessels.

Vasoconstrictor: A chemical substance whose actions result in the narrowing of blood vessels.

Vasodilator: A chemical substance whose actions cause an increase in the diameter of blood vessels.

Vasomotor: Pertaining to the muscles and nerves that control blood vessel diameter, thereby regulating or modulating blood pressure.

Ventral intermediate (VIM) nucleus: A specific region of the thalamus. This area of the brain is involved in the control of movement and is the "target" area for thalamotomy and deep brain stimulation when treating patients with tremor.

Ventriculography: Brain imaging method that uses an injected dye and X-rays to visualize the brain's ventricles (cavities)

Virulent: Referring to or characterized by virulence or the degree to which an invading microorganism, such as a bacterium or virus, is able to produce disease. Measures of virulence may be based upon the microorganism's ability to invade bodily tissues and the severity of the disease produced.

Visual-analog scale: This linear scale allows responses on a continuum.

Wearing off: The wearing-off phenomenon is a decrease in how long levodopa works. Over time, the ON state (the time in which the levodopa is effective) becomes shorter. The person returns to the OFF state (when the drug is not effective) more quickly after having taken levodopa. Wearing off is usually related to how long a person has been taking levodopa.

Wearing-off phenomenon: Wearing-off phenomenon is a decrease in how long Levodopa works. Over time, the ON state is shortened. The OFF state comes back quicker the more time a person takes the drug.

White matter: Bundles of myelinated nerve fibers or axons. These nerve fibers have a creamy white appearance due to myelin, a whitish substance that primarily contains fats and proteins. Myelin forms a protective, insulating sheath around certain axons, functioning as an electrical insulator and ensuring efficient nerve conduction. The breakdown, destruction, or loss of myelin from a nerve or nerves (demyelination), such as seen in certain neurodegenerative diseases, results in impaired nerve impulse transmission.

Wilson disease: A rare genetic disorder of copper metabolism, leading to an excessive accumulation of copper in certain tissues and organs, including the liver, brain, kidneys, or corneas of the eyes. Without prompt, appropriate treatment, the disorder may result in progressive liver disease, degenerative changes of the brain, psychiatric abnormalities, and other symptoms. Neurologic findings may include tremor; involuntary, rapid, jerky movements combined with relatively slow, writhing movements (choreoathetosis); impaired muscle tone and sustained muscle contractions, producing repetitive movements and abnormal posturing; increasingly slurred speech; and difficulties swallowing. Some patients may also experience increasing irritability, anxiety, severe depression, unusual behaviors, or other psychiatric problems.

X-linked dominant trait: Human traits, such as an individual's specific blood group, eye color, or expression of certain diseases, result from the interaction of one gene inherited from the mother and one from the father. In X-linked dominant disorders, the gene mutation for the disease trait is transmitted as a dominant gene on the X chromosome and therefore may "override" the instructions of the normal gene on the other chromosome, resulting in expression of the disease. Because females have two X chromosomes yet only one functioning copy is necessary, a percentage of X chromosomes with the mutated gene may not be expressed (random X chromosome inactivation). As a result, females often have less severe symptoms than affected males. In contrast, because males have one X chromosome from the mother and one Y chromosome from the father, those who inherit an X-linked dominant disease trait typically fully express the mutated gene on the X chromosome, causing a more severe form of the disorder that may result in lethality before or shortly after birth. Fathers with an X-linked dominant trait transmit the gene to their daughters but not to their sons. Mothers with a single copy of an X-linked dominant gene have a 50 percent risk of transmitting the gene to their daughters as well as to their sons.

X-linked recessive trait: Human traits, such as a person's eye color, specific blood group, or expression of certain diseases, result from the interaction of one gene inherited from the mother and one from the father. In X-linked recessive disorders, the gene mutation for the disease trait is located on the X chromosome. Because females have two X chromosomes yet only one functioning copy is necessary, a percentage of X chromosomes with the mutated gene may not be expressed (random X chromosome inactivation). However, because males have one X chromosome from the mother and one Y chromosome from the father, those who inherit an X-linked recessive disease trait typically fully express the mutated gene on the X chromosome. Some females who carry a single copy of the disease gene (heterozygous carriers) may have certain symptoms associated with the disorder; however, such findings are usually more variable and less severe than those seen in affected males. Fathers with an X-linked recessive trait may transmit the gene to their daughters but not to their sons. Mothers with an X-linked recessive gene have a 50 percent risk of transmitting the gene to their daughters and their sons.

Zydis: Unlike drugs that are incorporated into pills or capsules that must be swallowed, Zydis drugs are incorporated into fast-dissolving freeze-dried wafers that "melt" on the tongue. The term Zydis refers to the vehicle that is used for drug delivery and not to the drug itself.