The voltage-dependent P/Q-type calcium channel subunit alpha-1A (CACNA1A) gene has been implicated in epileptic encephalopathy, familial hemiplegic migraine, episodic ataxia, and spinocerebellar ataxia [46] and has recently been reported in a small number of atypical Rett patients previously lacking known genetic mutations [47]. The gene discussed is CACNA1A; the disease is familial hemiplegic migraine.