De novo mutations in ATP1A2 and CACNA1A are frequent in early-onset sporadic hemiplegic migraine

Objective: Hemiplegic migraine (HM) is a rare subtype of migraine with aura that may occur as a familial (FHM) or sporadic condition (SHM). Screening of FHM genes in previous series of patients with SHM detected a very low proportion of mutated patients. In this study, we investigated the FHM genes in patients with an early onset sporadic form of HM (onset before 16 years). Methods: Twenty-five patients were included. Each one and his or her 2 parents were blood sampled. Mean age at diagnosis was 14.7 ± 8.2 years and mean age at clinical onset was 7.7 ± 3.4 years. Sequencing of ATP1A2 and CACNA1A was conducted in each proband and all identified variants were looked for in both parents. SCN1A was screened in all patients without CACNA1A or ATP1A2 de novo mutation. Results: Twenty-three different amino acid variants were identified in 23 of the 25 patients. The variants occurred de novo in 19 patients (76%), strongly in favor of their causal role. SCN1A analysis did not show any mutation. Among the 19 patients with a de novo mutation, 5 had a pure HM and 14 had associated neurologic signs such as ataxia, epilepsy, or intellectual disabilities. Conclusions: FHM genes are involved in early-onset SHM, in particular when associated with neurologic signs. Molecular analysis can be helpful in those cases. Our study identified 14 novel de novo mutations that will help to interpret genetic tests in molecular diagnosis practice.