ATP1A2 and familial or sporadic hemiplegic migraine: Moreover, about 25 mutations were diagnosed in sporadic cases of hemiplegic migraine, SHM, (with overlap in the case of G815R, R908Q, P979L, which were identified in different unrelated pedigrees or individuals) showing that mutations in the ATP1A2 gene locus substantially account for de novo mutations causing hemiplegic migraine.