Abstracts

Rationale: To evaluate the effect of vagal nerve stimulation (VNS) on interictal epileptiform discharges (IEDs). Methods: Thirty-two epileptic patients (18 females; 14 males) with an average age of 42.2±11.4 years, all of whom had been suffering from epilepsy for an average of 29.2±14.5 years, participated in the study. All of the patients received VNS for at least 5 years. The first EEG was performed prior to the onset of stimulation; the second EEG was performed after 5 years of stimulation. We compared these two EEGs in terms of the number of IEDs present in each patient and correlated them to other variables. Results: The average total number of IEDs during EEG and the total number of seconds in which IEDs were present decreased after five years of stimulation from 97.3±106.9 resp. 80.6±86.1 to 49.4±94.0 resp. 37.8±65.0 (p=0.034). Although there was no positive correlation between the reduction of IEDs and the percentage of seizure reduction, we found a greater decrease of IEDs in patients who responded to VNS in comparison to those who did not (p=0.032). The decrease of IEDs was more pronounced in patients suffering from temporal lobe epilepsy than in patients suffering from extratemporal epilepsy (p=0.043). No other significant correlations were found. Conclusions: VNS reduced IEDs in patients chronically simulated for epilepsy. The reduction of IEDs was greater in patients who responded to VNS and in patients suffering from temporal lobe epilepsy.