Abstracts

Patients with mesiotemporal epilepsy have a better chance of achieving seizure freedom after epilepsy surgery than those with neocortical epilepsy. The risk of seizure recurrence depends on several factors. Previous studies revealed that interictal epileptiform activity (IEA) on post-operative EEG did not predict the risk of seizure recurrence. However, it is not known whether there is a difference based on the type of surgery. The aim of this study was to evaluate whether the relationship between IEA on post-operative EEG and seizure recurrence after epilepsy surgery is different in patients who underwent neocortical and mesiotemporal resections., We reviewed retrospectively the electronic medical records of patients who underwent epilepsy surgery at the Comprehensive Epilepsy Program of the University of Florida between January 1997 and December 2002. Post-operative follow-up clinic notes were reviewed up to the last clinic note to determine the recurrence of seizures. EEG reports of the post-operative EEG were reviewed to assess for the presence of IEA. Epileptiform abnormalities were defined as frank spikes or sharp waves or electrographic seizures., A total of 94 patients who had both adequate clinic follow-up and post-operative EEGs were identified. EEGs were performed on average 106 days after surgery and patients were followed in clinic on average 32 months after surgery. Seventy patients had mesiotemporal resections. Of those, 16 (23%) had IEA on their EEGs and 22 (31%) had seizure recurrence. A chi-square test revealed no significant relationship between seizure recurrence and the presence of IEA. Twenty four patients had neocortical resections. Of those, 14 (58%) had IEA and 12 (50%) had seizure recurrence. A chi-square test revealed a significant relationship between the presence of IEA and seizure recurrence (P = 0.013). However, 14 out of the 22 mesiotemporal and 8 out of the 12 neocortical surgery patients had seizure recurrence within 3 months after surgery, prior to the post-operative EEG., This study revealed that epileptiform activity on early post-operative EEG correlate with seizure recurrence in neocortical but not mesiotemporal surgeries. However, since most patients have seizure recurrence within three months after surgery, evaluation of the utility of earlier EEG is needed.,