CACNA1A and familial or sporadic hemiplegic migraine: Heterozygous variants in CACNA1A were historically associated with three well-defined neurological phenotypes: familial hemiplegic migraine type 1 (FHM1), episodic ataxia type 2 (EA2), and spinocerebellar ataxia type 6 (SCA6) [2, 3].