Impact of hippocampectomy on seizure freedom in temporal encephaloceles: A systematic review and individual participant data meta-analysis

Objective

Temporal encephaloceles (TEs) are increasingly recognized as a cause of MRI-negative temporal lobe epilepsy (TLE). The optimal surgical approach for TE-related refractory epilepsy remains unclear, particularly regarding the necessity of excluding mesiotemporal structures such as the hippocampus, which may lead to worse neuropsychological outcomes. This study evaluates the impact of hippocampectomy on achieving seizure freedom in patients with TE-related epilepsy through a systematic review and individual participant data (IPD) meta-analysis.

Methods

A systematic literature review was conducted across Medline, Google Scholar, Embase, and Web of Science, identifying studies reporting surgical outcomes in TE-related epilepsy. Studies were included if they provided at least 12 months of follow-up and reported seizure outcomes using Engel or ILAE classification. The primary outcome was postsurgical seizure freedom (Engel Class IA or ILAE Class 1). A mixed-effects logistic regression model was used to compare outcomes between patients who underwent hippocampectomy and those who did not. Heterogeneity was assessed using τ² and I² statistics.

Results

The meta-analysis included 23 studies with a total of 155 surgically treated patients. The primary analysis did not identify a statistically significant difference in seizure freedom between patients who underwent hippocampectomy and those who did not (Risk Ratio [RR] = 0.66, 95% Confidence Interval [CI]: 0.29–1.52, p = 0.329). Other covariates, including sex, duration of epilepsy, presence of additional epileptogenic lesions, and the use of invasive presurgical evaluation, were not significant predictors of seizure freedom. The I² statistic indicated moderate heterogeneity (54.68%).

Significance

This IPD meta-analysis suggests that hippocompectomy does not significantly impact seizure freedom in patients with TE-related epilepsy and should not be part of a universal approach when determining the optimal surgical strategy. These results reinforce the need for an individualized approach, considering patient-specific factors to optimize surgical decision-making in TE-related epilepsy.

Plain Language Summary

Temporal encephaloceles (TEs) can cause drug-resistant epilepsy, often requiring surgical management for seizure control. Given the variety of surgical techniques available, the optimal approach remains uncertain, particularly regarding the necessity of hippocampectomy, which may impact neuropsychological outcomes. This one-stage individual participant data meta-analysis found no significant difference in seizure freedom between patients who underwent hippocampectomy and those who did not. These findings suggest that hippocampectomy should not be routinely performed and highlight the importance of individualized surgical decision-making for patients with TEs.