Survival analysis of the surgical outcome of temporal lobe epilepsy due to hippocampal sclerosis

Purpose: Surgical results in patients with mesial temporal lobe epilepsy due to hippocampal sclerosis (MTLE/HS) are often reported in conjunction with other etiologies of TLE. Methods: We prospectively collected surgical outcome data for 2 to I I years for 134 consecutive patients who specifically had MTLE and unilateral HS, according to magnetic resonance imaging (MRI) and confirmed by histopathology. Sixty-five had postoperative neuropsychological testing. Outcome was analyzed by using Engel's classification (a) through Kaplan-Meier estimated survival curves (as a function of the time to seizure recurrence), (b) as percentage of patients in each outcome class on a yearly basis, and (c) at the last updated follow-up. Results: Kaplan-Meier estimates of complete seizure freedom (Engel's class IA) for years 1, 2, 5, and 10 were 85%, 77%, 74%, and 66%, and of Engel's class I were 89%, 86%, 83%, and 81 %. Only nine (6.7%) patients had outcome classes III or IV at any point during follow-up. Of the patients tested, 26% of those operated on the left side and 22% of those operated on the right had postoperative decline of > ISD in verbal or visual memory, respectively. Conclusions: High rates of seizure freedom can be obtained and remain stable over the years in patients operated on for unilateral MTLE/HS, even in countries with limited resources.