Kin, Taichi

BACKGROUND AND OBJECTIVES: Access to the amygdala and hippocampus (A/H) is complex. To address the limitations and invasiveness of traditional approaches, including the Transsylvian, Subtemporal, and Supracerebellar infratentorial approaches, we developed the suprapetrous infratemporal (SPIT) approach. This study describes the nuances of this approach in both cadaveric studies and clinical cases. METHODS: Three unilateral exposures were performed using microscopic and endoscopic methodologies in the SPIT approach. After cadaveric investigation, this approach was successfully implemented in representative clinical cases. RESULTS: The SPIT approach enabled direct access to the inferior A/H, circumventing the requirement for temporal lobe retraction and detachment of the temporal lobe from the dura through a subtemporal route by drilling the upper part of the mastoid, consequently mitigating tension on the vein of Labbé. This enabled a bottom-up view because one would gain with a zygomatic osteotomy and forward projection like a mini-posterior petrosal view by using a transmastoid view, without cutting down the zygomatic arch and opening the dura subtemporally, limiting patient pain and preventing case comorbidity. The SPIT approach was performed in 2 cases of mesial temporal cavernoma presenting with seizures. The lesion was visualized intraoperatively and was successfully removed in these cases. The postoperative course was excellent with no complications, and gross total resection was radiographically confirmed with Engel Class 1a seizure freedom. CONCLUSION: The SPIT approach is a complementary approach for inferior A/H disease, combining the combined middle fossa approach modified for intradural pathology. Limited drilling of the upper aspect of the mastoid with a medial dural opening at the level of the arcuate eminence provides a direct trajectory with minimal brain retraction. Additional research encompassing a larger patient cohort and extended follow-up periods is required to substantiate the advantages of SPIT in the management of inferior A/H lesions.

Abstract Central nervous system hemangioblastoma (CNS HB) is a benign but highly vascular tumor, which accounts for 1.7% of all intracranial tumors. CNS HBs predominantly arise in the cerebellum, brainstem, and spinal cord. Approximately 20% of CNS HB is related to von-Hippel-Lindau (VHL) disease and repeated surgical resections are often required in VHL patients due to the presence of multiple CNS HBs. To explore the differences of surgical effect between VHL disease related and sporadic CNS HBs, outcome analyses were performed based on the tumor locations. PATIENT AND METHODS: A total 83 cases that underwent surgical resections of CNS HBs at Tokyo University in 1996-2019 were included. Clinical information including age, sex, number of past surgical resections, pre- and post-operative modified Rankin Scale(mRS) were examined. RESULTS: Regarding the etiology, 46 VHL cases(cerebellum:30, medulla oblongata:6, spinal cord:10) and 37 sporadic cases (cerebellum: 28, medulla oblongata:4, spinal cord:5) were enrolled. The average changes in the postoperative mRS minus preoperative mRS were cerebellum -0.9/medulla oblongata -0.5/spinal cord -0.8 for VHL cases, and cerebellum -0.75/medulla oblongata -1/spinal cord -1 for sporadic cases. Fisher`s exact tests were used for between-group comparison. DISCUSSION: The study showed no statistically significant difference between cerebellar and spinal cord cases regarding the perioperative change in the patient capability. Because of multiple lesions and repeated surgeries, VHL patients have a possibility to present with worse neurology after surgery. Further analysis is needed to clarify differences in surgical outcome for VHL disease related and sporadic related CNS HBs.