Authors: Shehryar Sheikh; Nicholas Thompson, MS; Lara Jehi, MD (Cleveland, OH)

Introduction: Success in epilepsy surgery is most commonly judged by post-operative seizure frequency. We wished to identify whether absolute post-operative seizure frequency, absolute reduction in seizure frequency, or relative seizure frequency reduction best predicted patient-reported quality of life after epilepsy surgery. Methods: We prospectively surveyed patients at outpatient visits to the Cleveland Clinic Epilepsy Center before and after receiving epilepsy surgery (n=550), between 2007 and 2017. The QOL measure of interest was the previously validated Quality of Life in Epilepsy (QOLIE-10) score at the patient’s most recent office visit. We used a multivariate linear regression model to predict post-operative QOLIE-10. Variables included in the model included pre-operative QOLIE-10 as well as pre-operative and post-operative depression score (PHQ9), anxiety score (GAD7), absolute seizure frequency, absolute reduction in seizure frequency, relative reduction in seizure frequency, follow-up time, and relevant interaction terms. Results: For the 550 patients included in the analysis, median follow-up time was 24.7 months (IQR8.5-54.5). Our model provided good prediction of post-operative QOLIE-10 (R 2 =0.72, P<0.001). Effect tests demonstrated that the most important predictive variables were post-operative PHQ9 (F=75, p<0.001), pre-operative QOLIE-10 (F=14, p<0.001), and relative seizure reduction (F=11, p=0.0012). Absolute seizure reduction, absolute post-operative seizure frequency. and follow-up time did not show statistically significant effects. Conclusion: Our results demonstrate that patients are likely to report a high quality of life after epilepsy surgery as long as there is a significant relative reduction in their seizure frequency after surgery, even if the absolute seizure frequency reduction is non-zero. Most literature evaluating surgical outcomes in epilepsy uses Engel classification to classify surgical success, which focuses on absolute seizure frequency and ignores patient-reported quality of life outcomes. QOL measures should play a bigger role in the evaluation of surgical outcomes.