Expanding the Genetic and Clinical Spectrum of SCN1A-Related Hemiplegic Migraine: Analysis of Mutations in Japanese

Familial Hemiplegic migraine (FHM) is characterized by repeated episodes of reversible localized neurological deficits, in addition to headache. The aura of HM includes visual, sensory, motor, and verbal symptoms. HM is classified into non-familial sporadic HM (SHM) and familial HM (FHM). Here, we analyzed the clinical symptoms and their relevance in four Japanese patients considered to have SCN1A mutations as a cause. Sequencing of SCN1A was performed using the Sanger method in 50 blood samples from clinically suspected patients with FHM. Subsequently, algorithm analysis, allele frequency determination, and three-dimensional structure analysis of the recognized variants were performed, and the recognized variants were evaluated. We found five heterozygous missense mutations (p.A23E, p.V250L, p.T398M, p.R1575C, p.L1660I) in SCN1A, three of which had not been reported. These five mutations may also affect the structure of the protein products, as assessed using a three-dimensional structural analysis. In all cases, the clinical symptoms included visual, sensory, motor, and verbal symptoms, which are forms of aura. Similarities were detected, such as the appearance of symptoms at a young age and other symptoms, such as hemiplegia after a headache attack. We report five missense mutations in SCN1A of Japanese cases.