CACNA1A and familial or sporadic hemiplegic migraine: However, heterozygous mutations in the CACNA1A gene have also been identified in spinocerebellar ataxia type 6 (SCA6, MIM 183086) and familial hemiplegic migraine type 1 (FHM1, MIM 141500), which share with EA2 the allelic autosomal dominant mode of inheritance [8,9].