Abstracts

Rationale: Seizure freedom is generally considered to be higher in lesional temporal lobe epilepsy (TLE) vs. non-lesional TLE. However, there is currently no universal definition for non-lesional TLE, making comparisons difficult. This study is the first to develop a standardized stringent definition for NLTLE, incorporating both imaging and histopathological modalities in the criteria. We also analyze long-term post-operative outcome objectively with Engel Classification, and subjectively with patient report on mental health state and quality of life (QOL). Methods: We defined non-lesional TLE (NLTLE) as normal pre-operative MRI (MRI-), abnormal hypometabolic pre-operative FDG-PET (PET+), and normal post-operative histopathology (Hist-). All patients had received epilepsy surgery at St. Vincent's Hospital Melbourne, a tertiary referral epilepsy centre, between 1994-2011. Retrospective medical records analysis and prospective interviews using standardized validated questionnaires, which included modified Columbia Seizure Diagnostic , QOLIE 31, QOLIE 10, and NDDI-E, were performed. Seizure scoring was based on two years post-operative and at time of interview using Engel & ILAE Classification. Results: 37 of 401 patients were identified with NTLE. Mean duration of follow-up was 8.7 years (range 2.8 - 16.3). Preliminary analysis demonstrated 87.5% had objectively improved seizure control (Engel class 3>), with 62.5% good surgical outcome (Engel Class I & II) and 53% excellent surgical outcome (Engel Class 1). In addition, 22% no longer required anti-epileptic medications. 60% have reported good current QOL, scoring greater than 8 out of 10, and 72% reported QOL improvement of more than 50% compared to before surgery. Lowered mood was screened in 31%. Conclusions: NLTLE appears to have a good long-term surgical outcome with comparable seizure freedom rates similar to published TLE series, and high quality of life. This demonstrates NLTLE may have a more optimistic surgical outcome than previously inferred and should be welcomed as an avenue for further exploration.