The Lennox-Gastaut syndrome: electroencephalographic characteristics, clinical correlates, and follow-up studies.

Electroencephalographic and clinical findings are reported for 100 patients with the Lennox-Gastaut (LGS) triad of slow bilateral spike and wave (BSW), retardation and multiple seizures. Neurological and mental deficits were frequently observed, especially in patients who developed seizures before age 1 yr. More than half of the patients had focal epileptiform discharges that peaked in occurrence at age 4-6 yrs. EEG follow-up showed that background frequency slowed when patients developed the LGS pattern, and increased after recovery. Only 2 patients developed normal EEGs on follow-up, although 22 patients no longer showed the LGS pattern after an average of 3 yrs 3 mos follow-up.