Effect of valproic acid treatment on spike-wave discharge patterns during sleep and wakefulness

7 patients suffering from absences were recorded before antiepileptic treatment, in the early phase of valproate monotherapy and after having reached steady state. Recordings made with the Oxford-Medilog 4-channel cassette recorder were analyzed visually as well as by a computerized s-w pattern recognition approach, the latter facilitating quantification of pattern characteristics (number, amplitudes and duration of spikes and waves). Measurements were made separately for epochs of wakefulness and sleep. Compared to the premedication phase the amount of s-w discharges in 24 h showed an average reduction of more than 90%. For the majority of the patients, 24-hour discharge profiles showed a maximum in the early morning. Duration and amplitude of both spike and wave elements was higher during sleep. For the waking state, the ratio wave amplitude/spike amplitude was found to be increased under medication.