Steckley et al. (2001) presented a large Canadian kindred of Mennonite heritage with an autosomal dominant episodic ataxia clinically distinct from other reported episodic ataxias. Vestibular ataxia, vertigo, tinnitus, and interictal myokymia were prominent. Attacks were diminished by ... Steckley et al. (2001) presented a large Canadian kindred of Mennonite heritage with an autosomal dominant episodic ataxia clinically distinct from other reported episodic ataxias. Vestibular ataxia, vertigo, tinnitus, and interictal myokymia were prominent. Attacks were diminished by acetazolamide. At least 26 members of the family were affected; 12 described frequent bouts of interictal myokymia. Myokymia was visible in 1 patient upon examination. Steckley et al. (2001) distinguished the disorder in their family from the features of EA1 by noting the presence, in their family, of vertigo and tinnitus, neither of which is typical of EA1. Similarly, the absence of interictal nystagmus and shorter episodes distinguished this disorder from EA2 (108500). The variable age of onset contrasted with the typical EA1 onset of late childhood or early adolescence, and the typical childhood onset of EA2. Although vertigo and tinnitus were also prominent in periodic vestibulocerebellar ataxia (PATX; 606552), Steckley et al. (2001) noted that PATX differs in having abnormal eye movements, including abnormal smooth pursuit, nystagmus, and abnormal vestibuloocular reflex; no response to acetazolamide; and absence of interictal myokymia.