STXBP1 as a Novel Gene for Sleep-Related Hypermotor Epilepsy: A Video-EEG Documented Case Report

Objectives:Sleep-related hypermotor epilepsy (SHE) is a rare syndrome that presents with hyperkinetic, asymmetric, tonic/dystonic seizures, mainly during sleep. Certainty of diagnosis can be categorized into 3 levels: witnessed (possible) SHE, video documented (clinical) SHE, and video-EEG documented (confirmed) SHE. The role of various genes has previously been reported. The STXBP1 gene is phenotypically associated with early infancy epileptic encephalopathy 4. It's also been linked to Ohtahara Syndrome, West Syndrome, and Dravet Syndrome. We present a patient with confirmed SHE who had a STXBP1 gene mutation. Case Report:A nine-year-old girl was admitted to our video-EEG unit for seizure and sleep disorder differentiation. She experienced rapid and aimless movements, particularly in her extremities, after waking up unexpectedly at night and rising in bed. Her seizures began at the age of five. While on antiepileptic medication, she reported an increase in seizures during the prior two months. In her video EEG recordings, the background rhythm was appropriate for her age, and ictal activity began in the left frontotemporal area. Her seizures were classified as focal onset impaired awareness hyperkinetic seizures. A heterozygous mutation in the STXBP1gene was detected by genetic analysis. This mutation, which is associated with Dravet Syndrome, was detected for the first time in a case of confirmed SHE. Discussion:Genetic causes are one of the identified SHE etiologies. The presented case extends the list of SHE-related genes to include STXBP1.The conventional phenotypic features caused by this gene mutation were more severe than our patient's. Future functional studies may reveal genotype-phenotype concordance.
Keywords: Sleep-related hyper motor epilepsy, sllep disorders, video-EEG