CACNA1A and familial hemiplegic migraine: CACNA1A mutations are the cause of episodic ataxia type 2 (EA2) (Ophoff et al., 1996), familial hemiplegic migraine (FHM) (Ophoff et al., 1996), and spinocerebellar ataxia type 6 (SCA6), a CAG triplet repeat expansion disorder (Zhuchenko et al., 1997).