Alterations in transient visual-evoked potentials induced by clonazepam and sodium valproate

The transient visual-evoked potentials (VEP), recorded in patients suffering from generalized epilepsy, can be characterized by a duplication of the negative peak with a latency of 70-100 ms, a strong increase in amplitude of the negative peak between 80 and 130 ms and the development of a high amplitude slow negative wave following the primary complex. In this study we have investigated to which degree these changes are influenced by the intravenous administration of clonazepam and sodium valproate. Therefore, VEPs were registered in 30 patients, suffering from generalized epilepsy, just before and immediately after the intravenous injection of 0.4-0.8 mg clonazepam and further at 15, 30 and 16 min thereafter. The same procedure was applied on 10 patients treated with an intravenous injection of 400 mg sodium valproate. In both groups we found more or less a reduction in number and degree of the mentioned VEP changes. The improvement was associated with a strong decrease in amplitude of the VEP components in the group treated with clonazepam but was not seen in the sodium valproate group.