Absence epilepsy with fast rhythmic discharges during sleep: An intermediary form of generalized epilepsy?

Purpose: To describe a particular form of absence epilepsy (AE) characteriz ed by an atypical EEG pattern (fast rhythmic discharges) during sleep and a n unfavorable course with the persistence of seizures at a late age and dru g resistance. Methods: We reviewed the medical files of 31 patients diagnosed with AE at our institution been 1995 and 1999 for whom an EEG during sleep had been re corded. Patients with fast rhythmic discharges during sleep were selected f ur the study. Results: Five patients showed the usual criteria of childhood absence epile psy (CAE) or juvenile absence epilepsy (JAE)but with fast discharges of rhy thmic spikes (10-15 Hz) during sleep, such as those typically observed in L ennox-Gastaut syndrome. Four patients were of adult age at the time of the last examination. Intellectual capacities were "borderline" in each case, w ith visible social and learning handicaps. Absences were the initial seizur e event in all patients, but four patients developed generalized tonic-clon ic seizures during the course of the disease. Treatment using a combination of antiabsence drugs such as valproate and lamotrigine led to only margina l improvement. Conclusions: These findings illustrate the utility of sleep EEG in detectin g the fast rhythmic discharges that are markers of drug resistance in AE an d suggest the existence of transitional forms of AE that are intermediate b etween idiopathic and cryptogenic/symptomatic generalized epilepsies.