SPECTRAL EEG DURING SHORT-TERM DISCONTINUATION OF ANTIEPILEPTIC MEDICATION IN PARTIAL EPILEPSY

The effect of short-term discontinuation of antiepileptic drugs (AEDs) on spectral analysis of EEG background activity (spectral EEG) was st udied in patients undergoing preoperative evaluation for epilepsy surg ery. We also wished to clarify whether AED discontinuation would provi de lateralizing evidence in spectral EEGs of patients with temporal lo be epilepsy (TLE). Spectral EEGs were performed in 15 patients receivi ng their regular medication regimen and again after a 1-week period du ring AED withdrawal. A subgroup of 9 patients who had previously under gone temporal lobectomies (TLE group) was studied separately. In this group, we evaluated the effect of preceding seizures on spectral EEG d erived from temporal neocortical areas. In all patients, spectral EEG changes were detected even after a short-term AED withdrawal. The tota l amount of absolute delta activity was reduced and occipital peak fre quency and relative alpha activity were increased as compared with bas eline values. In TLE patients with habitual seizures occurring <20 h b efore the spectral EEG recording, lateralization was correctly identif ied by the greater amount of absolute delta activity ipsilateral to th e epileptogenic focus. Epileptic seizures are accompanied by subtle fo cal slowing in spectral EEG for a much longer period than has been ass umed. In addition, postictal spectral EEG over the temporal lobes may have lateralizing value, Further studies in larger numbers of patients are needed to evaluate the role of spectral EEG in the preoperative e valuation of patients for temporal lobe surgery.