[Severe infant myoclonic epilepsy (author's transl)].

Twenty children (15 males and 5 females) suffering from a particular type of myoclonic epilepsy were submitted to a longitudinal study. All children were neurologically normal. Familial antecedents existed for epilepsy in 25% of the cases (5/20) and for febrile convulsions in 15% (3/20). The first fit appeared with fever at the mean age of 6 months in all cases but one of clonic type. Frequent similar febrile or afebrile clonic seizures recurred in all subjects before the age of 12 months. At this time the EEG was normal in 14 cases and brief discharges of generalized spike-waves during ILS or during sleep were present in 6 cases only. Later, frequent non-febrile clonic unilateral or generalized fits, frequent atypical 'absences' often accompanied by jerks, high photosensitivity and non-epileptic erratic myoclonias appear. Nevertheless, atomic and/or tonic seizures did not appear. The evolution is characterized by the persistence of fits and the appearance of severe language disorder and light cerebellar and pyramidal signs. The authors present their results and discuss the nosological problems of this severe infant myoclonic epilepsy.