Two novel SCN1A mutations identified in families with familial hemiplegic migraine.

Background: Familial hemiplegic migraine (FHM) is a rare monogenic subtype of migraine with aura, characterized by motor auras. The majority of FHM families have mutations in the CACNA1A and ATP1A2 genes; less than 5% of FHM families are explained by mutations in the SCN1A gene. Here we screened two Spanish FHM families for mutations in the FHM genes.

Methods: We assessed the clinical features of both FHM families and performed direct sequencing of all coding exons (and adjacent sequences) of the CACNA1A, ATP1A2, PRRT2 and SCN1A genes.

Results: FHM patients in both families had pure hemiplegic migraine with highly variable severity and frequency of attacks. We identified a novel SCN1A missense mutation p.Ile1498Met in all three tested hemiplegic migraine patients of one family. In the other family, novel SCN1A missense mutation p.Phe1661Leu was identified in six out of eight tested hemiplegic migraine patients. Both mutations affect amino acid residues that either reside in an important functional domain (in the case of Ile(1498)) or are known to be important for kinetic properties of the NaV1.1 channel (in the case of Phe(1661)).

Conclusions: We identified two mutations in families with FHM. SCN1A mutations are an infrequent but important cause of FHM. Genetic testing is indicated in families when no mutations are found in other FHM genes.