18. The electroencephalogram (EEG) in patients with Lennox–Gastaut syndrome continuing into adulthood

Abstract

Purpose: To study the long-term clinical and EEG evolution of Lennox–Gastaut syndrome, a chronic and severe epileptic encephalopathy. Methods: Patients presenting with seizure types and EEG discharges typical of LGS were diagnosed at the age 2–7 years and included in the follow-up extended to adulthood. Results: The study sample consisted of 23 patients (9 females and 14 males, mean age at onset 3.6 years, average follow-up period 19.8 years). Three main clinical and EEG stages were found: 1. Full-blown stage with intractable seizures or epileptic status and long bilateral slow spike-wave discharge, 2. Diminished seizure frequency and short, irregular EEG discharges, and 3. Seizure remission with low amplitude and slow EEG activity. At the end of follow-up, 5 patients were still in full-blown stage, 7 reached second stage, while a stable remission with persistent cognitive and mental disorders occurred in 11 patients. Long-lasting BSSWC episodes remitted at an earlier age than bilateral tonic spike discharges during sleep. Conclusion: Severe epileptiform EEG abnormalities were concomitant with high seizure frequency and severity, while scanty and slow EEG activity with rare or absent epileptiform abnormalities was associated with severe sequels of LGS.