Hippocampal tumor resection: assessment of clinical outcomes

Introduction: Hippocampal tumors present challenges for resection due to the functional importance of the hippocampus and its surrounding structures. Resection carries significant potential for perioperative morbidity and entails a delicate balance between achieving sufficient tumor removal and preserving cognitive and neurological function. Literature detailing hippocampal tumors remains sparse, with few groups having reported their surgical results. We contribute to an expanding narrative by presenting a comprehensive account of a single institution’s experience with hippocampal tumors.

Methods: Adult patients who underwent resection of hippocampal tumors at Memorial Hermann Hospital between 2004 and 2022 were included. Clinical data were collected from electronic medical records, and tumors were manually segmented to calculate volumes (cm3) and extent of resection (EOR).

Results: We identified 78 patients (24 females; ages 19–82) who had resection of hippocampal tumors. 54 (69%) patients had high-grade tumors (HGT) and 24 (31%) had low-grade tumors (LGT). The median preoperative tumor volume was 40cm3 (range 1.5–219.22). The most common presenting symptoms were seizures (n=39) and headaches (n=28). 1 (1%) patient experienced an intraoperative complication, and 11 (14%) experienced complications in the immediate postoperative period. The median EOR was 86% (range 4.6–100%). 2 weeks postoperatively, 30 (38%) patients presented with neurological deficits. Notably, greater EOR was significantly associated with higher rates of memory deficits at this time point (p=0.019). 3-months postoperatively, 19 (24%) patients had persistent deficits. Tumor progression was identified in 36 (67%) HGT and 8 (33%) LGT. Median OS was 28.2 months (95% CI 24.6–30) for HGT and 65 months (95% CI 61.3–69.5) for LGT. Interestingly, EOR was predictive of OS and progression-free survival (PFS) for HGT (p=0.008 and p< 0.001, respectively) but not LGT (p=0.156 and p=0.581, respectively).

Conclusion : Hippocampal tumor resection can be accomplished with an acceptable morbidity profile. While aggressive resection is associated with increased OS for high-grade tumors, a more conservative resection may be suitable for low-grade tumors given the increased short-term memory deficit risk without survival benefit in this subgroup.