Abstracts

Rationale: Long-term cost and adverse effects due to postoperative anti-epileptic drugs (AEDs) use are of concern in patients who have achieved seizure freedom by surgery. The aim of this study is to determine whether early AED withdrawal is possible in a select patient group presenting with mesial temporal lobe epilepsy (MTLE) and concordant epileptogenic zone (EZ) from standard presurgical evaluations. Methods: This retrospective study evaluated 317 pharmacoresistant MTLE patients who underwent anterior temporal resection from 2004 to 2008. Patients (n = 148) selected in this study had both unilateral hippocampal sclerosis determined by MRI and were seizure-free after surgery (Engel class Ia). In addition, patients (n = 67) met the criteria for high concordance in localizing the EZ as defined by congruence in clinical semiology, interictal EEG, ictal EEG, and high-resolution MRI using epilepsy protocol. We categorized the patients into 3 groups according to the time period between surgery and withdrawal from AEDs: (A) 6 months, (B) 1 year, and (C) 2 years. Patients were subsequently followed-up from 6 to 51 months (mean 46.2 months) after the start of AEDs withdrawal to determine if they maintained seizure freedom. Kaplan-Meier method was used to analyze the primary end point of recurrent seizures. Recurrence-free survival was measured from the date of AEDs withdrawal to the date of relapse. Log-rank test was used to compare recurrence-free survival curves. Results: A total of 67 patients were found to meet the criteria of being seizure-free, having HS, and concordant in all four diagnostic tests. Within this sub-group of patients, 26 were in group A, 12 in group B, and 18 in group C. Eleven patients were maintained on AEDs and not included in the analysis. There were no significant differences in age, gender, age of seizure onset, lateralization of EZ, and surgical procedure among the 3 groups. Throughout the follow-up period, 88.5%, 91.7% and 88.9% of patients remained seizure-free in group A, B and C, respectively. No significance was noted in recurrence-free survival curves among the three groups (p = 0.933). Conclusions: In MTLE patients with highly concordant EZ, the risk for seizure relapse after surgery appears to be no greater for those who withdrew AEDs at 6 months than for those who withdrew at either 1 or 2 years after surgery. AED withdrawal at 6 month postoperatively should be possible in seizure-free MTLE patients who have highly concordant presurgical evaluations. In developing countries with limited resources, these results may be beneficial in epilepsy care management.