Aetiology

The gene for familial hemiplegic migraine is on chromosome 19 and codes for the neuronal P/Q voltage-gated calcium channel (VGCC).

Diseases caused by dysfunction of ion-channel proteins are characterised by fluctuation in severity and are termed channelopathies.

Antibodies to VGCC are seen in the Eaton-Lambert myasthenic syndrome. Mutations in the VGCC are also seen in episodic ataxia type 2.

Notes:

• other cases of familial hemiplegic migraine have been found to be caused by mutations in the ATP1A2 gene, which encodes the alpha2 subunit of the Na+/K+ pump, and in the SCN1A gene for the neuronal voltage-gated sodium channel (2)

Reference:

1. Ophoff RA, Terwindt GM, Vergouwe MN, van Eijk R et al. . Familial hemiplegic migraine and episodeic ataxia type-2 are caused by mutations in the calcium channel gene CACNLA4. Cell 1996;87: 543-52.
2. BMJ 2006 Jan 7;332(7532):25-9.