Episodic Ataxia Type 2 (EA-2)

Inheritance
Autosomal dominant

Molecular genetics and pathogenesis
EA-2 is due to a loss-of-function mutation in a protein that controls electrical activity in brain cells.

The same gene is mutated in SCA 6, but with a CAG repeat expansion, and in familial hemiplegic migraine, with a missense mutation.

Clinical manifestations
The episodic ataxias are, as their name indicates, episodic rather than progressive. The ataxic spells are triggered by startle, fever, heat, or physical or emotional stress.

The ataxic spells of EA-2 are longer than those of EA-1, lasting days. Episodes may occur as often as several times per week or as infrequently as once or twice per year. In the spell-free interval, the patient may experience several types of ocular abnormalities. Migraine is also common. Patients in advanced stages of EA-2 may develop chronic ataxia.

Treatment
Acetazolamide is an effective treatment for many patients. Treatment typically begins at 125 mg/day, increasing as high as 500 mg twice daily.

4-aminopyridine has shown efficacy in small trials.

References
OMIM
http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=108500

Jen JC, Graves TD, Hess EJ, Hanna MG, Griggs RC, Baloh RW; CINCH investigators. Primary episodic ataxias: diagnosis, pathogenesis and treatment. Brain. 2007 Oct;130(Pt 10):2484-93.
PMID: 17575281

Strupp M, Zwergal A, Brandt T. Episodic ataxia type 2. Neurotherapeutics. 2007 Apr;4(2):267-73.
PMID: 17395137

	Friedreich Ataxia