[Familial hemiplegic migraine]

Familial hemiplegic migraine (FHM) is a rare subtype of migraine with aura. It is inherited as an autosomal dominant trait. A gene for FHM has been assigned to chromosome 19. This gene codes for a brain-specific calcium channel, and is responsible for FHM in 55% of the FHM families. Other FHM families have been linked to two different locations on chromosome 1. These locations contain possible candidate genes coding for calcium-and potassium channels. Thus FHM is a genetically heterogenous ion channel disorder, which is caused by at least three different genes. About 29% of the FHM families also have cerebellar ataxia, these families have all been linked to chromosome 19. The identification of the genes for FHM may be a key to the identification of the gene/genes for migraine with and without aura.