CACNA1A and familial or sporadic hemiplegic migraine: Different types of monoallelic mutations in CACNA1A, which encodes the voltage‐gated P/Q‐type calcium channel subunit alpha‐1A, are associated with a number of different phenotypes, including SCA6 (OMIM# 183086),53 episodic ataxia type 2 (EA2; OMIM# 108500),54 familial hemiplegic migraine type 1 (FHM1; OMIM# 141500)55 with or without progressive cerebellar ataxia, benign paroxysmal torticollis of the infancy,56 early infantile epileptic encephalopathy,57 and paroxysmal head tremor.58