[Juvenile myoclonic epilepsy (Janz syndrome). A well-known epilepsy syndrome?].
Juvenile myoclonic epilepsy (JME) was described electroclinically by Janz and Christian in 1957 and consists of myoclonic jerks in varying combination with the absence of seizures and generalized tonic-clonic seizures, a typical circadian distribution on awakening, sleep deprivation, alcohol consumption and flickering stimuli as characteristic precipitating factors, typical EEG abnormalities with generalized epileptiform discharges, normal physical and neuroradiological findings, and often a family history of epilepsy. Although the misdiagnosis of this well-classified and easily treatable syndrome is supposed to occur rarely in Germany, we retrospectively investigated how often the wrong initial classification had been made among patients who were finally treated in our outpatient epilepsy unit. Between 1993 and 1995, 30 patients with a typical JME-like symptom constellation were identified who had been misdiagnosed initially. In all patients, localization-related epilepsy had been classified, although regional EEG abnormalities were rare (n = 5). All patients reported the typical circadian distribution, abnormal neuroradiological findings were absent, and typical EEG abnormalities were present in all cases. Under treatment with appropriate antiepileptic drugs 97% of the patients became almost completely seizure-free. Even 40 years after the first description of the syndrome, JME is an underdiagnosed illness. The generally positive course underlines the importance of its correct identification.