Extrapial Hippocampal Resection in Anterior Temporal Lobectomy: Technical Description and Clinical Outcomes in a 62-Patient Case Series.

BACKGROUND Anterior temporal lobectomy (ATL) is the most effective treatment for drug-resistant mesial temporal lobe epilepsy. Extrapial en bloc hippocampal resection facilitates complete removal of the hippocampus. With increasing use of minimally invasive treatments, considering open resection techniques that optimize the integrity of tissue specimens is important both for obtaining the correct histopathological diagnosis and for further study. OBJECTIVE To describe the operative strategy and clinical outcomes associated with an extrapial approach to hippocampal resection during ATL. METHODS A database of epilepsy surgeries performed by a single surgeon between October 2011 and February 2019 was reviewed to identify all patients who underwent ATL using an extrapial approach to hippocampal resection. To reduce confounding variables for outcome analysis, subjects with prior resections, tumors, and cavernous malformations were excluded. Seizure outcomes were classified using the Engel scale. RESULTS The surgical technique is described and illustrated with intraoperative images. A total of 62 patients met inclusion criteria (31 females) for outcome analysis. Patients with most recent follow-up 3 yr (n = 29) exhibited 79% and 52% class I outcomes, respectively. An infarct was observed on postoperative magnetic resonance imaging in 3 patients (1 asymptomatic and 2 temporarily symptomatic). An en bloc specimen in which the subiculum and all hippocampal subfields were preserved was obtained in each case. Examples of innovative research opportunities resulting from this approach are presented. CONCLUSION Extrapial resection of the hippocampus can be performed safely with seizure freedom and complication rates at least as good as those reported with the use of subpial techniques.