Benign myoclonic epilepsy in infants: electroclinical features and long-term follow-up of 34 patients.

Purpose: Benign myoclonic epilepsy in infants (BMEI) is a rare epileptic syndrome characterized only by generalized myoclonic seizures (MSs) in normal children during the first 2 years. Our aim was to assess the electroclinical features and the follow-up of this syndrome.

Methods: BMEI was confirmed by electroencephalogram (EEG) in four neuropediatric units in France between 1981 and 2002. Clinical and electroencephalographic findings at diagnosis and during the follow-up were collected. The Vineland scale or Wechsler scale or both were used to perform neuropsychological evaluations.

Results: We report 34 patients with BMEI characterized by MSs occurring many times a day. The ictal EEG showed a generalized discharge of polyspikes, polyspikes-and-waves, or spikes-and-waves. The interictal EEG was usually normal. A family history of febrile seizures (FSs) or epilepsy was noted in six patients. A history of FSs was noted in 11 patients. Eleven patients had reflex MSs. Monotherapy with valproic acid was effective in 23 of 30 treated patients. The onset of epilepsy was known in all patients. Four patients had seizures after the initial symptoms. Juvenile myoclonic epilepsy developed in two patients, and cryptogenic partial epilepsy in another. Neuropsychological outcome was evaluated in 20 patients (10 with Wechsler scales and 17 with the Vineland scale). Cognitive functions were normal in 17 patients, whereas developmental delay was observed in three others.

Conclusions: BMEI is clinically characterized by myoclonic seizures involving the upper part of the body, occurring many times a day. The ictal EEG showed a generalized discharge of polyspikes, polyspikes-and-waves, or spikes-and-waves. The interictal EEG was usually normal. Reflex MSs were frequently observed, suggesting that two distinctive syndromes are not necessary. BMEI may be followed by juvenile myoclonic epilepsy. Despite a generally favorable neuropsychological outcome, mental retardation can be observed more frequently than in the general population.