Antiepileptic drug effects on somatosensory evoked potentials

Abstract

Some evoked potential changes have been documented in chronic phenytoin (PHT), valproate (VPA), or benzodiazepine therapy, whereas other studies have suggested little change with carbamazepine (CBZ) or phenobarbital (PB). We recorded median and posterior tibial nerve somatosensory evoked potentials (SEPs) in complex partial seizure patients taking PHT, CBZ, or VPA in monotherapy with stable therapeutic serum levels and no toxic symptoms. Ten patients each were studied with PHT, CBZ, and VPA and were compared with age-matched controls. Median nerve responses were recorded at Erb's point, cervical spine, and contralateral cerebral sites; tibial nerve evoked potentials were recorded from popliteal fossa, lumbar, cervical spine, and midline scalp electrodes. Epileptic patients and controls did not differ in SEP latency, amplitude, or central condition time. PHT prolonged Erb's point and popliteal fossa latencies, but not central conduction time. CBZ had no effect on latencies or amplitudes. Evoked potential amplitudes were reduced by VPA, and cortical response latencies were minimally prolonged. Chronic antiepileptic therapy without toxicity had little effect on SEPs. PHT may have a slight effect on peripheral nerve conduction, and VPA may have an effect on amplitude of cerebral responses.