Motor cortex excitability in seizure-free STX1B mutation carriers with a history of epilepsy and febrile seizures.

OBJECTIVE: Mutations in STX1B encoding the presynaptic protein syntaxin-1B are associated with febrile seizures with or without epilepsy. It is unclear to what extent these mutations are linked to abnormalities of cortical glutamatergic or GABAergic neurotransmission. We explored this question using single- and paired-pulse transcranial magnetic stimulation (TMS) excitability markers.

METHODS: We studied nine currently asymptomatic adult STX1B mutation carriers with history of epilepsy and febrile seizures, who had been seizure-free for at least eight years without antiepileptic drug treatment, and ten healthy age-matched controls. Resting motor threshold (RMT), and input-output curves of motor evoked potential (MEP) amplitude, short-interval intracortical inhibition (SICI, marker of GABAA ergic excitability) and intracortical facilitation (ICF, marker of glutamatergic excitability) were tested.

RESULTS: RMT, and input-output curves of MEP amplitude, SICI and ICF revealed no significant differences between STX1B mutation carriers and healthy controls.

CONCLUSIONS: Findings suggest normal motor cortical GABAA ergic and glutamatergic excitability in currently asymptomatic STX1B mutation carriers.

SIGNIFICANCE: TMS measures of motor cortical excitability show utility in demonstrating normal excitability in adult STX1B mutation carriers with history of seizures.