Ataxia: Genetic Testing and Counseling

Genetic Tests
Genetic testing includes:

• Diagnostic testing—used to determine presence or absence of a disease gene in a patient with symptoms
• Predictive testing—used to determine if a non-symptomatic person at risk for a genetic disorder carries a disease gene (Only patients who reached the age of majority can be tested; for many reasons (best addressed by a genetic counselor), predictive testing of minors is not recommended
• Carrier testing—used to determine if a person carries an autosomal recessive disease gene, usually for family planning purposes
• Prenatal testing—used to determine the genetic status of a pregnancy at risk for a genetic disorder
• Preimplantation testing—used to determine the genetic status of an embryo before implantation in assisted reproduction
• Newborn screening—used to determine the presence or absence of one or more disease genes in a newborn, for purposes of early intervention

Genetic testing is available for many, but not all, genes that cause ataxia. Test availability may be limited by:

• Absence of known genetic cause
• Excess of causative mutations
• Rarity of disorder

Other tests may be offered by research groups in the context of ongoing research projects. As the techniques of genetic analysis advance, the number of commercially available tests will increase. An up-to-date list of tests and testing centers can be found at www.genetests.org.

Genetic Counseling
Genetic counseling is a critical accompaniment to genetic testing. Genetic counseling provides the patient and family:

• Medical information about the genetic condition, including inheritance, penetrance, and risk
• Counseling to allow the patient and family to make the best decisions regarding whether to test, and how to use the information gained from it.
• Information about the options available for family planning and other issues

Multiple issues arise in every genetic testing situation. These differ among diseases, and depend as well on the patient's age, marital status, current health, personal outlook, and many other factors.

Issues affecting the decision of whether to test may include:

• Availability of treatment
• Desire of the patient to know his or her prognosis
• Ability of the patient to handle life-transforming health information (whether the result is positive or negative)
• Concerns over confidentiality of results
• Concerns over implications of a test result for other family members
• Concerns over genetic discrimination in the workplace or for insurance
• For prenatal testing, acceptance by the parents of the option of pregnancy termination

It should be noted that information gained from testing one member of a family may necessarily provide some information to other members, who may not want this information, or want it to be shared with other family members. For example, if a presymptomatic individual learns she has inherited the SCA-1 gene, her children carry a 50% risk of having inherited the gene from her. Those children may not want to know their risk, or may be too young to make an informed decision about learning their genetic status. In such a case, the parent may choose to forego the test, or to keep the results confidential.

A positive test result obviously presents the patient and family with significant and potentially life-transforming information and post-test counseling is crucial in order that obtaining the test result remain a beneficial event for the patient.

A negative test result can also have profound consequences, and in some cases those consequences may be negative. A person whose life has been shaped by the potential of a late-onset disease such as an inherited ataxia may find it difficult to adjust to the new prospect of a long life with all its attendant responsibilities. A person not carrying a gene that affects or that will affect a sibling may feel "survivor's guilt," and have difficulty resolving those feelings without counseling.

	Spinocerebellar Ataxia 1 (SCA1)