In 2 Italian sisters with familial hemiplegic migraine (141500) and late-onset cerebellar ataxia and cerebellar atrophy, Battistini et al. (1999) identified an arg583-to-gln (R583Q) mutation in a putative voltage sensor domain of the CACNA1A gene. The frequency and severity of the attacks increased near the sixth decade for both patients, when the cerebellar signs developed. Acetazolamide was effective prophylactic therapy.
Terwindt et al. (2002) studied 27 patients with sporadic hemiplegic migraine and found the R583Q mutation in a 16-year-old boy with no cerebellar signs.
In a large Portuguese family in which 17 patients over 4 generations were affected with hemiplegic migraine and/or progressive cerebellar ataxia-6 (SCA6; 183086), Alonso et al. (2003) found that all patients shared a common haplotype and carried the R583Q mutation. Mean age at onset for hemiplegic migraine symptoms was in the second decade and onset of cerebellar signs was approximately 20 years later. Four patients, all under the age of 18 years, had only hemiplegic migraine, 8 patients had isolated progressive cerebellar ataxia, and 5 patients had both hemiplegic migraine and cerebellar ataxia. Several patients reported symptoms triggered by minor head trauma. Alonso et al. (2003) postulated that the mutation, which occurs in a transmembrane segment of the voltage sensor of the channel, may cause a shift in the voltage dependence of the channel, leading to an increase in intracellular calcium. They suggested that episodic ataxia-2 (108500), SCA6, and familial hemiplegic migraine are not only allelic disorders, but may be the same disorder with great phenotypic variability.
De Vries et al. (2007) identified a 2021G-A transition in the CACNA1A gene, resulting in an R583Q substitution, in a patient who developed FHM at age 13 years. The mutation was also identified in his mother, who had migraine with aura. The findings suggested either reduced penetrance or a common pathogenetic mechanism for both hemiplegic and nonhemiplegic migraine.
