Episodic ataxia type 2 is a rare autosomal dominant paroxysmal ataxia syndrome caused by mutations in CACNA1A, the gene for the calcium channel. It is characterized by episodes of ataxia (poor coordination and balance), vertigo, nausea, vomiting, nystagmus, and dysarthria. Some individuals also experience diplopia, tinnitus, headache, weakness, or dystonia.

Attacks may be triggered by stress, exercise, caffeine, alcohol, or fever. Episodes typically last hours to days and can occur once a year to a few times per week. Onset is typically in childhood or adolescence. Although patients are largely normal between attacks initially, 50%-80% develop progressive ataxia and most display interictal nystagmus. Patients also have an increased risk of epilepsy, and about 50% suffer from migraines.