Definition:

Episodic ataxias (EAs) are a group of rare autosomal-dominant diseases characterized by recurrent, discrete episodes of ataxia, giddiness, and vertigo. EA1 and EA2 are the most widely recognized of the autosomal-dominant EAs and are caused by dysfunction of neuronal voltage-gated ion channels. There are central and peripheral nervous system manifestations in both conditions. The current classification is based on genetics and actually includes seven distinct subtypes. But these variants other than EA1 and EA2 are rare, some only occurring in single families, and gene mutations have not been identified in all. It is quite likely, however, that the number of phenotypes and mutated genes will grow further.