Graded extent of hippocampal resection is related to neuropsychological outcomes in temporal lobe epilepsy surgery

OBJECTIVE: Surgical resection for epilepsy seeks to maximize seizure freedom while minimizing new neurocognitive impairments. Tailored resections guided by anatomoelectroclinical (AEC) hypotheses offer the possibility of sparing parts of the hippocampus. The relationship between the extent of hippocampal resection and postoperative neurocognitive outcomes in this context has not been studied and has important implications for clinical practice. We test this relationship in a series of left and right tailored anterior temporal lobectomy (ATL) surgeries. METHODS: We conducted a retrospective analysis of 34 adult patients with drug-resistant temporal lobe epilepsy (18 left, 16 right) who underwent tailored ATL based on individualized AEC hypotheses at the University of Pittsburgh Medical Center. All patients completed standardized pre- and postoperative neuropsychological testing, and 85.3% underwent preoperative stereoelectroencephalography to guide resection. Surgical extent was tailored through a multidisciplinary process integrating AEC correlations and intraoperative electrophysiology. Preoperative and postoperative hippocampal volumes were measured and correlated with changes in verbal and visual memory, as well as language performance. RESULTS: Greater extent of resection of the left hippocampus was significantly associated with worse postoperative outcomes in both verbal and visual recall. Extent of resection of the right hippocampus was not related to reductions in performance across any domain, with some indication of improvements in performance after right ATL surgery at the group level. Seizure outcomes (66.6% Engel I at 2 years) were consistent with the existing literature and did not vary with hippocampal resection extent. SIGNIFICANCE: These findings highlight the critical role of the left hippocampus in supporting both verbal and visual memory and underscore the importance of preserving hippocampal tissue during left ATL when feasible. Our results support the utility of AEC-guided tailored resections as a strategy to balance seizure control with cognitive preservation.