Abstracts

Rationale: Various factors have been tested for associations with post-surgical outcome in refractory temporal lobe epilepsy (TLE) such as gender, age at onset, duration of epilepsy, history of febrile convulsions, auras and hippocampal asymmetry. The aim of our study was to assess whether intracranial monitoring and side of surgery are correlated with surgical outcome in patients with mesial TLE due to hippocampal sclerosis (HS) confirmed by pathology. Methods: Following IRB approval, we retrospectively searched the Henry Ford electronic database to identify patients older than 18 who had epilepsy surgery in our institution, minimum post surgical outcome 6 months, MRI suggestive of mesial temporal pathology and histopathological diagnosis of mesial temporal sclerosis. We classified outcome at the most recent follow-up based on Engel’s classification (class I=no seizures, class II=rare disabling seizures, class III=worthwhile improvement, class IV =no improvement). We collected patient demographics, age at epilepsy onset and surgery, MRI, video scalp or invasive EEG monitoring localization, and number of antiepileptic drugs (AEDs) before and after surgery. We used descriptive statistics and chi-square to test for correlation between outcome and intracranial monitoring or side of surgery. Results: Sixty two patients (35 females) with a mean age of 46.27.3±11.69 years and mean follow up of 39.11±11.37 months were included in the study. Mean age at epilepsy surgery was 39.11±11.37 years. MRI was consistent with temporal pathology (temporal atrophy and/or HS) in all and questionable in 2 patients. Intracranial monitoring was done in 28 patients (45.16%) due to inconclusive findings from non-invasive procedures. Left anterior temporal resection was done in 31 patients (50%). Outcome was class I in 45 patients (72.6%), II in 3 patients (4.8%) and III and IV in 14 patients (22.6%). Mean number of AEDs before surgery was 2.19±0.06 (range 1-3) and after 1.74±0.65 (range 0-3). After surgery 61.5% of patients were on the same number of AEDs and 32.8% on fewer. One additional AED was added in 1 patient and 1 patient achieved long-term seizure freedom off AEDs. Although seizure freedom was achieved in 82% of patients who did not undergo preoperative intracranial monitoing and 64 % of those who did, no statistical significance was reached (Fisher’s exact test 0.14). Of those who had left temporal resection, 80% became seizure free compared to 68% of those after right temporal lobe resection. However, the results did not reach statistical significance (Fisher’s exact test 0.38). Conclusions: Surgical treatment of mesial TLE due to HS is associated with favorable outcome (class I and class II) in 77% of patients. Our study showed that seizure outcome is not associated with preoperative intracranial monitoring or side of surgery in patients with mesial TLE. Therefore, these two variables are not predictors of post-surgical outcome in mesial TLE.