CACNA1A and migraine, familial hemiplegic, 1: Familial hemiplegic migraine 1 (FHM1) is in the majority of cases caused by a missense mutation of the CACNA1A gene that codes for the pore-forming subunit of the neuronal voltage-gated calcium channel Cav2.1, leading to gain-of-function effects that result in hyperexcitability [83, 91].