[Polygraphical sleep study on typical absence: relationship between the effect of sodium valproate and nigrostriatal...

In order to clarify the mechanism of the effect of sodium valproate (VPA) on absence seizures, we performed sleep polygraph recordings in 10 patients with typical absence. VPA was effective in six cases (group A), partially effective in two (group B), and ineffective in two (group C). In 5 of 9 cases, the tonic sleep components were abnormal. In 4 cases, the percentage of slow wave sleep increased before administration of VPA, and did not change remarkably by its administration. In group A and B, twitch movements (TM), one of the phasic sleep components detected in the mentalis muscle on surface EMG, decreased or were unchanged after administration of VPA, especially during the REM period. In contrast, TM increased in group C. We speculate that the changes of TM (especially in the REM periods) after administration of VPA are well related to its effectiveness. Since TMs are thought to be controlled by the nigrostriatal dopaminergic pathway, the different response of basal ganglia to VPA among cases with absence epilepsy would have some relation to the different effectiveness of VPA in controlling seizures.