Sleep-related hypermotor epilepsy and peri-ictal hypotension in a patient with syntaxin-1B mutation

STX1B is a gene that encodes syntaxin-1B. STX1B mutations have recently been implicated in fever-associated epilepsy syndromes. However, these have not previously been reported in sleep-related hypermotor epilepsy. A 20-year-old man with a strong family history of epilepsy was investigated in our epilepsy monitoring unit due to uncontrolled epilepsy, compatible with sleep-related hypermotor epilepsy. Electroclinical and polygraphic physiological recordings revealed left frontal epileptiform discharges and prominent peri-ictal hypotension. Normal MRI using an epilepsy protocol prompted a search for a genetic epilepsy, which revealed a likely pathogenic mutation in the STX1B gene. The patient remained seizure-free after treatment optimization with carbamazepine. This case suggests that a sleep-related hypermotor epilepsy phenotype can be associated with syntaxin-1B gene mutation, and testing for this gene should be considered in such patients. Furthermore, it may also be concluded that autonomic dysfunction, characterized by peri-ictal hypotension, can also occur in this discorder. [Published with video sequences on www.epilepticdisorders.com].