Clinical and electroencephalographic findings prior to the onset of juvenile myoclonic epilepsy: A case series.

OBJECTIVE: The purpose of this study was to investigate the timing of generalized electroencephalographic abnormalities in patients with juvenile myoclonic epilepsy who were followed up long-term before the onset of juvenile myoclonic epilepsy.

METHODS: We enrolled juvenile myoclonic epilepsy patients whose course of epilepsy had been observed for more than five years before the onset of juvenile myoclonic epilepsy, those who had undergone electroencephalogram recording more than twice before the onset of juvenile myoclonic epilepsy, and those who had terminated antiseizure medications for at least two years before the onset of juvenile myoclonic epilepsy. Patients who had transitioned from childhood absence epilepsy to juvenile myoclonic epilepsy were excluded. We retrospectively reviewed the medical records and neurophysiological data of the patients.

RESULTS: Four patients met the inclusion criteria. One patient was diagnosed with febrile seizures during childhood, and the remaining three had transitioned to juvenile myoclonic epilepsy from other epileptic disorders, such as self-limited epilepsy with autonomic seizures, genetic epilepsy with febrile seizure plus, or non-specific genetic generalized epilepsy. All patients exhibited generalized spike-wave discharges or photoparoxysmal responses for more than two years before the onset of juvenile myoclonic epilepsy.

SIGNIFICANCE: The four patients had transitioned to juvenile myoclonic epilepsy from other epileptological preconditions. Patients with juvenile myoclonic epilepsy may show generalized electroencephalographic abnormality many years prior to the onset of symptoms. Generalized spike-waves on electroencephalogram during the course of any type of epilepsy or febrile seizure may be a risk factor for developing juvenile myoclonic epilepsy.