Autosomal dominant episodic ataxia: a heterogeneous syndrome.

We describe six kindreds with autosomal dominant episodic ataxia, apparently representing three distinct syndromes. Four kindreds were characterized by episodic ataxia and response to acetazolamide, and in three, interictal nystagmus. One kindred was characterized by paroxysmal ataxia and in one member, paroxysmal choreoathetosis. The last kindred had brief attacks of ataxia and interictal neuromyotonia. The age of onset and severity of the disorder varied within each kindred. These kindreds illustrate the heterogeneity of episodic ataxia as well as the variable expressivity within each kindred.