Anatomical Determinants of Epilepsy Surgery Outcomes: A Systematic Review and Individual Patient Data Meta-Analysis

ImportanceTo date, epilepsy surgery outcomes remain highly variable, with seizure freedom rates hovering around 50-70%, highlighting the need for a deeper understanding of the factors influencing surgical success. ObjectiveTo conduct an individual patient data meta-analysis of epilepsy surgery outcomes in drug-resistant epilepsy, leveraging granular, patient-level data to identify key clinical, demographic, and anatomical factors that influence surgical success. Data SourcesMEDLINE (via Ovid), Embase, and Scopus were searched from inception to August 9, 2024. Study SelectionPrimary studies reporting patient-level surgical outcomes and clinical information in patients with drug-resistant epilepsy. Data Extraction and SynthesisData were abstracted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Unique patient data from 385 studies were pooled, yielding 5,588 patients with outcomes, localization, demographics, pathology, and other findings. Surgical success rates were reported with 95% Wald confidence intervals. Main Outcome(s) and Measure(s)Measured outcomes were surgical success rates (% Engel 1/ ILAE 1-2) based on key patient and disease-specific factors. Statistical associations were tested with chi-squared tests (p<0.05), effect sizes measured with Cramers V, and post-hoc comparisons adjusted using the false discovery rate. ResultsSurgical success rates (Engel I/ILAE 1-2) have remained stable over the past decades (r=0.25, p=0.13), while seizure freedom rates (Engel Ia/ILAE 1) have significantly improved (r=0.59, p<0.01). This occurred alongside a rise in surgical interventions, including more complex cases, as indicated by increased stereo-EEG use, and the adoption of minimally invasive techniques. Surgical success varied significantly by lobar anatomy ({chi}2=52, p<0.01), with the highest success rates in temporal (68.6% [67.0-70.1%]) and insular lobes (66.2% [55.4-77.0%]), although only temporal outcomes were statistically significant. Multilobar resections had lower success rates, with outcomes varying significantly by lobar combination ({chi}2=25, p=0.02). Variability in outcomes were also influenced by histopathology and MRI findings ({chi}2=121, p<0.001), and the type of surgical intervention ({chi}2=30.5, p<0.001). Conclusions and RelevanceThis meta-analysis combined patient-level data from multiple studies to understand how individual patient characteristics influence surgical outcomes. Identifying these prognostic factors can guide more personalized patient selection and surgical planning, and ultimately improve rates of favorable outcomes in epilepsy surgery. Key PointsO_ST_ABSQuestionC_ST_ABSWhat are the main factors influencing surgical success in drug-resistant epilepsy patients? FindingsA systematic review of 5,588 individual patient data from 385 primary research studies showed that the anatomical region, surgical technique, and histopathological diagnosis impact epilepsy surgery outcomes, with varying success rates based on these factors interaction. MeaningPresurgical evaluations and research into potential biomarkers and treatment options should consider these patient-specific factors instead of relying on generalized, population-level outcome statistics.