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Episodic Ataxia Type 1.


GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2014.
2010 Feb 09 [updated 2012 Aug 16].



Episodic ataxia type 1 (EA1) is a potassium channelopathy characterized by constant myokymia and dramatic episodes of spastic contractions of the skeletal muscles of the head, arms, and legs with loss of both motor coordination and balance. During attacks some individuals may experience vertigo, blurred vision, diplopia, nausea, headache, diaphoresis, clumsiness, stiffening of the body, dysarthric speech, and difficulty in breathing. EA1 is associated with an increased incidence of epilepsy. Other findings can include delayed motor development, cognitive disability, choreoathetosis, and carpal spasm. Onset is in childhood or early adolescence.


Diagnosis is based on clinical findings and molecular genetic testing of KCNA1, the only gene in which mutations are known to cause EA1.


Treatment of manifestations: Acetazolamide (ACTZ), a carbonic-anhydrase (CA) inhibitor, may reduce the frequency and severity of the attacks in some but not all affected individuals. Antiepileptic drugs (AEDs) may significantly reduce the frequency of the attacks in some individuals. Prevention of primary manifestations: In addition to pharmacologic treatments, behavioral measures including avoidance of stress, abrupt movements, loud noises, and caffeine intake may be used to reduce disease manifestations both in a symptomatic or an asymptomatic person. Prevention of secondary complications: Joint contractures can be prevented by appropriate physiotherapy. Surveillance: Annual neurologic examination. Agents/circumstances to avoid: General anesthetics have occasionally been reported to precipitate or aggravate neuromyotonia.


EA1 is inherited in an autosomal dominant manner. Most individuals diagnosed with EA1 have an affected parent; to date, only one de novo mutation has been reported. Each child of an individual with EA1 has a 50% chance of inheriting the mutation. Prenatal diagnosis for pregnancies at increased risk is possible if the disease-causing mutation has been identified in an affected family member.

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