Slow spike-wave activity in EEG and associated clinical features: often called 'Lennox' or "Lennox-Gastaut' syndrome.

Clinical features were studied in 83 patients with slow spike-wave activity in the EEG. Epileptic seizures, usually intractable, occurred in 82 patients. The majority had the onset of seizures during the first 2 years of life. Minor motor seizures alone or in combination with other types of seizures occurred in 80 percent, and most had more than one type of seizure. The combination of tonic-clonic, minor motor, and absence seizures was the commonest, occurring in 37 percent. Sixty-six patients were definitely retarded and 49 showed definite motor impairment. Etiologic factors responsible for cerebral insult were identified in 53 patients. Serial EEG studies showed a close relationship between the EEG patterns of hypsarrhythmia, independent multifocal spike discharges, and slow spike-wave activity. The eponym "Lennox-Gastaut" syndrome is appropriate for a patient who has slow spike-wave activity in the EEG, exhibits mental retardation, and has intractable seizures of various types. However, the syndrome does not imply a pathologic entity because many diverse processes, both static and progressive, can produce this syndrome.