Introduction: Medically-refractory epilepsy is a challenging disorder to treat, especially in patients who have failed resection. Current evidence regarding outcomes of repeat epilepsy surgery is limited to small case series, often with conflicting results. Therefore, our group performed a quantitative meta-analysis on available data from the past 30 years to assess for rates and predictors of success.

Methods: A PubMed search was conducted for studies reporting outcomes of repeat epilepsy surgeries from 1986-2016. Studies were excluded if they contained fewer than 5 patients, had median follow up < 1 year, or did not report disaggregated outcomes. Patients who underwent non-resective interventions were excluded. Outcomes were dichotomized into freedom from disabling seizures vs. persistent seizures, and then stratified by each variable. Variables of interest were evaluated with formal meta-analysis using a random effects model.

Results: 509 patients who received repeat epilepsy surgery from 20 studies were included. Freedom from disabling seizures (Engel I outcome) was observed in 47.5% of patients after repeat surgery. Significant predictors of seizure freedom in these patients included lesional over nonlesional epilepsy (odds ratio [OR] 1.86, 95% confidence interval [CI] 1.45-2.43), temporal lobe over extratemporal/multilobe resection (OR 1.64, 95% CI 1.21-2.30), abnormal over normal pre-operative MRI (OR 1.65, 95% CI 1.26-2.21), congruent over non-congruent EEG data (OR 1.6, 95% CI 1.2-2.1), and surgical over disease-related factors as the reason for initial resection failure (OR 3.9, 95% CI 2.1-9.6).

Conclusions: Here we provide the first quantitative meta-analysis of predictors of success in repeat epilepsy surgery. Predictors of favorable outcome in repeat surgery resemble those reported with initial epilepsy surgery. Overall, nearly half of patients undergoing repeat surgery achieved seizure freedom, suggesting further resection should be considered in patients who fail initial surgery and meet other positive criteria.

Patient Care: Here we provide the first quantitative evidence of rates and predictors of success in repeat epilepsy surgery across all the data in the current literature. Our work reveals that nearly half of patients who undergo repeat surgery achieve seizure freedom, suggesting further resection should be considered in patients who fail an initial intervention. Furthermore, we have identified factors that predict seizure freedom in this patient population, enabling clinicians to be better informed about their surgical case choices and prognosis for success.

Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe what a good case for repeat epilepsy surgery might look like 2) Discuss which elements of a case predict successful repeat epilepsy surgery, and supporting evidence 3) Identify which elements of a case are not predictive of successful repeat surgery 4) Discuss the significance and meaning of elements that predict successful repeat surgery

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