LATERALIZATION OF EVENT-RELATED POTENTIALS DURING DISCONTINUATION OF ANTIEPILEPTIC MEDICATION

The effect of short-term withdrawal of antiepileptic drugs (AEDs) on a uditory event-related potentials (ERPs) was studied in 16 patients und ergoing preoperative evaluation for epilepsy surgery. ERPs were perfor med for all patients during treatment with full medication and after a 1-week period during ongoing tapering of AEDs. To clarify whether AED discontinuation would provide evidence of lateralizing for ERPs, we a lso studied the subgroup of 9 patients who had already undergone tempo ral lobectomies (TLE group). In the TLE group, if habitual seizures oc curred <30 h before the ERP recording session, auditory N1 and P3 ampl itudes across sphenoidal electrodes were markedly decreased on the sid e ipsilateral to the epileptic focus. If seizures did not occur, asymm etries in amplitudes were equivocal and not of lateralizing value. In the whole group, midline N1 latencies for standard responses decreased significantly during AED discontinuation. At baseline, long-term habi tuation of the N1 component for standard responses was attenuated as c ompared with that of controls. During AED discontinuation, however, en hanced habituation of N1 was observed in TLE patients who did not exhi bit seizures before ERP recording.