Initially, mutations in the CACNA1A gene were identified in patients with familial hemiplegic migraine (FHM) (MIM#141500) or episodic ataxia type 2 (MIM#108500) [4], in that phenotypes acetazolamide may prevent recurrence and improve symptoms [5]. The gene discussed is CACNA1A; the disease is episodic ataxia type 2.