Myoclonic status epilepticus in juvenile myoclonic epilepsy.

BACKGROUND: Myoclonic status epilepticus (MSE) is rarely found in juvenile myoclonic epilepsy (JME) and its clinical features are not well described. We aimed to analyze MSE incidence, precipitating factors and clinical course by studying patients with JME from a large outpatient epilepsy clinic.

METHODS: We retrospectively screened all patients with JME treated at the Department of Neurology, Medical University of Innsbruck, Austria between 1970 and 2007 for a history of MSE. We analyzed age, sex, age at seizure onset, seizure types, EEG, MRI/CT findings and response to antiepileptic drugs.

RESULTS: Seven patients (five women, two men; median age at time of MSE 31 years; range 17-73) with MSE out of a total of 247 patients with JME were identified. The median follow-up time was seven years (range 0-35), the incidence was 3.2/1,000 patient years. Median duration of epilepsy before MSE was 26 years (range 10-58). We identified three subtypes: 1) MSE with myoclonic seizures only in two patients, 2) MSE with generalized tonic clonic seizures in three, and 3) generalized tonic clonic seizures with myoclonic absence status in two patients. All patients responded promptly to benzodiazepines. One patient had repeated episodes of MSE. Precipitating events were identified in all but one patient. Drug withdrawal was identified in four patients, one of whom had additional sleep deprivation and alcohol intake. Two patients received inappropriate treatment (carbamazepine, phenytoin).

CONCLUSIONS: MSE is a rare event in JME. Precipitating factors are commonly identified and for such cases the treatment response and outcome are excellent, in contrast to other cases with unknown causes.