Mutations of the CACNA1A gene, coding for the alpha subunit of Cav 2.1 channels, are the cause of two other allelic disorders, Spinocerebellar ataxia 6 (SCA6) and Familial Hemiplegic Migraine 1 (FHM1). The gene discussed is CACNA1A; the disease is familial or sporadic hemiplegic migraine.