Focal epilepsy due to de novo SCN1A mutation

OBJECTIVE Our aim was to identify patients with SCN1A-related epilepsy with a phenotype of pure focal epilepsy. METHODS We conducted a retrospective study and a systematic review in Pubmed to identify patients with focal epilepsy associated with SCN1A pathogenic variants. RESULTS We found three patients among 1,191 in our rare epilepsy database in 2017. The literature search from January 2000 to September 2019 led to identification of four patients with limited data. Our three patients had a common phenotype with focal-onset seizures as the only seizure type. All patients showed normal psychomotor development in the first years of life, and no intellectual disability although they displayed some cognitive or behavioural problems. Fever or hyperthermia were triggers in all three patients. In addition, all had a history of brief recurrent febrile seizures in their first year, followed by a phenotype of pharmacoresistant focal epilepsy with normal brain imaging. Two of them were initially investigated for epilepsy surgery. Seizure precipitation by fever has also been reported in previously published patients. SIGNIFICANCE Focal epilepsy associated with SCN1A gene mutation should be recognized in patients with suggestive features, in particular among surgical candidates.