Withdrawal of antiepileptic drugs during presurgical video-EEG monitoring: an observational study for evaluation of current practice at a referral center for epilepsy

OBJECTIVES: Withdrawal of antiepileptic drugs (AEDs) before and during video-EEG-monitoring is commonly implemented to reduce time needed to register a sufficient number of seizures during presurgical evaluation. There are, however, few guidelines regarding withdrawal rate and observation time. MATERIAL AND METHODS: We performed an observational study including sixty patients admitted to the national Norwegian epilepsy centre and registered tapering of AEDs and their effect on seizure rate and possible complications. RESULTS: The mean daily seizure rate before admission to the EMU was 0.4 (range 0.02-4) increasing to 1.1 (range 0-8) at the EMU. 29 patients (48%) followed a slow tapering rate whereas 31 (52%) had an intermediate tapering rate. There was no significant difference between the patients with a daily seizure rate during LTM of more or <0.7 seizures per day, an increase of seizure frequency from habitual to during LTM of more or <3.3 or 6.9 with regard to rate of tapering (slow vs intermediate) etiology or AED monotherapy vs polytherapy. Twenty-six patients (43%) had a sufficient number of seizures registered within 3 days to conclude regarding the presurgical evaluation. Two patients received escape treatment while 25 patients did have 24 h-seizure-clusters. There was no serious event. CONCLUSIONS: Less than 50% of the patients got a sufficient number of seizures for a conclusive result within 3 days. An increase in the registration period could increase the number of successful registrations.