Analytic study of epileptic absence seizures and effect of sodium valproate treatment

Two hundred and seventy eight absence seizures were recorded from 60 patients by an intensive monitoring device. They were divided into two subtypes, typical and atypical absences based on their ictal discharges whether the spike-wave rhythm was at 3 cps or not. These two absence seizures did not differ so much with regard to loss of consciousness except that: 1) the durations of discharge in atypical absences were longer than those of typical ones, 2) the recovery from clouded consciousness to a state of full-awareness was apparently delayed in atypical absences after the termination of epileptic discharges, 3) the oral automatisms were more associated with typical absences and the decreased postural tones with atypical absences. By a numerical analysis of two parameters of spike-wave, that is, its frequency ad rhythmicity, it was shown that absences with spike-waves slower than 30 cps and with poor rhythmicity which roughly corresponded with atypical absences were more therapy-resistant in comparison with those having 3 cps spike waves and good rhythm which were usually typical absences. Sodium valproate was more effective on typical absences, however, there was no difference between typical and atypical absences in the therapeutic maintenance concentrations of serum valproate acid. We would like to emphasize that the comparison of the symptomatology between typical and atypical absences is of significance not only for understanding the etiology of the epilepsies but for the guideline of practical pharmacotherapy.