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Episodic Ataxia Type 2.


Spacey S1.


GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2019.
2003 Feb 24 [updated 2015 Oct 15].

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Division of Neurology, University of British Columbia, Vancouver, British Columbia, Canada



Episodic ataxia type 2 (EA2) is characterized by paroxysmal attacks of ataxia, vertigo, and nausea typically lasting minutes to days in duration. Attacks can be associated with dysarthria, diplopia, tinnitus, dystonia, hemiplegia, and headache. About 50% of individuals with EA2 have migraine headaches. Onset is typically in childhood or early adolescence (age range 2-32 years). Frequency of attacks can range from once or twice a year to three or four times a week. Attacks can be triggered by stress, exertion, caffeine, alcohol, fever, heat, and phenytoin; they can be stopped or decreased in frequency and severity by administration of acetazolamide or 4-aminopyridine. Between attacks, individuals may initially be asymptomatic but commonly develop interictal findings that can include nystagmus, pursuit and saccade alterations, and ataxia.


The diagnosis of EA2 is established by identification of a heterozygous pathogenic variant in CACNA1A.


Treatment of manifestations: Acetazolamide is effective in controlling or reducing the frequency and severity of attacks in most individuals; typical starting dose is 125 mg a day given orally, but doses as high as 500 mg twice a day may be required. Acetazolamide is generally well tolerated; the most common side effects are paresthesias of the extremities, rash, and renal calculi. Acetazolamide does not appear to prevent the progression of interictal symptoms. Studies have also demonstrated that 4-aminopyridine in doses of 5-10 mg/3x/day can also be effective in reducing attack frequency and duration. Surveillance: Annual neurologic examination. Agents/circumstances to avoid: Phenytoin has been reported to exacerbate symptoms.


EA2 is inherited in an autosomal dominant manner. Most individuals with a diagnosis of EA2 have an affected parent. The proportion of cases caused by de novo pathogenic variants is unknown. Offspring of affected individuals have a 50% chance of inheriting the pathogenic variant. Prenatal testing is possible for pregnancies at increased risk for EA2 if the pathogenic variant has been identified in the family.

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