Severe myoclonic epilepsy in infancy: evolution of seizures.

Changes in seizure type of severe myoclonic epilepsy (SME) in infancy were reviewed retrospectively in 14 patients (11 males and 3 females) who were followed-up to the age of 7 years or more. The observation period ranged from 5 to 16 years with a mean of 10 years. During the follow-up, three or four types of seizures were seen per patient, but the pattern of appearance and disappearance of each seizure type varied considerably among the patients. Tonic-clonic convulsion, either generalized or unilateral, was seen most consistently through the entire course, and it continued to the end of follow-up in 11 patients (79%). On the contrary, myoclonic seizure, complex partial seizure, and atypical absence often disappeared and reappeared repeatedly during the course. In SME, seizure symptoms varied widely among patients in comparison with other neurological symptoms, and the most consistent core seizure type was tonic-clonic convulsions.