Epilepsy surgery outcomes and their determinants: a systematic review and individual patient data meta-analysis

BACKGROUND: Despite advances in epilepsy surgery, seizure freedom is achieved in only ~50-70% of cases, highlighting the need to better understand factors driving surgical success. METHODS: A preregistered systematic review and individual patient data meta-analysis was conducted on studies reporting clinical outcomes in epilepsy surgery, based on a comprehensive literature search through August 2024. Data were extracted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Unique patient data from 385 studies were pooled, yielding 5588 patients with outcomes, localisation, demographics, pathology and other findings. Surgical success rates (% Engel 1/ILAE 1-2) were reported with 95% Wald CIs. Associations with patient- and disease-specific factors were assessed using chi-squared tests (p<0.05), effect sizes with Cramer's V, and post hoc comparisons adjusted using the false discovery rate. RESULTS: Surgical success varied by lobar anatomy (χ²=52, p<0.001, V=0.12), with the highest success rates in temporal (68.6% (67.0% to 70.1%)) and insular lobes (66.2% (55.4% to 77.0%)). Multilobar resections had lower success rates, with outcomes varying by lobar combination (χ²=25, p=0.02, V=0.22). Variability in outcomes was influenced by histopathology and MRI findings (χ²=121, p<0.001, V=0.16; highest success in tumours (78.2% (74.9% to 81.6%))) and by surgical intervention (χ²=30.5, p<0.001, V=0.07; lowest success with corpus callosotomy (43.4% (35.4% to 51.5%))). Overall surgical success rates remained stable over time (r=0.25, p=0.13), despite surgery being extended to more complex patients. CONCLUSIONS: These findings inform surgical planning for drug-resistant epilepsy, emphasising individual patient characteristics to guide personalised treatment, improve outcomes and reflect the growing complexity of intersecting factors. PROSPERO REGISTRATION NUMBER: CRD42024530397.