Introduction: Fourth ventricular masses pose a significant surgical challenge, often requiring a telovelar approach. Early reports suggest that endoscopy may provide improved visualization in selected cases. Neither the role of neuroendoscopy nor its postoperative complication rate for this indication are well established.

Methods: We retrospectively reviewed patients who underwent endoscope-assisted fourth ventricular tumor resections using a standard suboccipital approach from 2011-2017. The angled endoscope was introduced following completion of microscopic tumor resection. Patient demographics, preoperative status, surgical details, pathology, and postoperative complications were analyzed.

Results: Eight patients were included in the analysis. Preoperative symptoms included headache (n=7, 87.5%), nausea and gait disturbance (n=4, 50.0%), vomiting and dizziness (n=3, 37.5%), and blurry vision and dysphagia (n=2, 25.0%). In 3 cases (37.5%), microscopic visualization was unfavorable and the endoscope was used to achieve >90% of tumor resection and/or restoration of CSF flow. In 1 case (12.5%), CSF flow was re-established and =50% of tumor was microscopically resected, while neuroendoscopy was used to complete additional tumor resection. In 4 cases (50%), neuroendoscopy was strictly used to confirm extent of resection and restoration of CSF flow. Postoperative pathology included 2 ependymomas, 2 rosette-forming glioneuronal tumors, 1 pilocytic astrocytoma, 1 metastatic melanoma, 1 epidermoid cyst, and 1 organized hematoma. Six patients (75.0%) underwent subtotal resection, 1 (12.5%) underwent gross total resection, and 1 (12.5%) underwent biopsy and cyst fenestration. Median length of stay was 18 days (range 5-42 days). Postoperative complications included one instance each of arm weakness, tracheostomy, intractable hiccups, and ventriculitis.

Conclusions: Neuroendoscopy was used to resect additional tumor or re-establish CSF flow during half of endoscopic-assisted fourth ventricular tumor resections. No instances of morbidity attributed to neuroendoscopy developed. Our series demonstrates the feasibility of supplementing microsurgical approaches to the 4th ventricle using neuroendoscopy, across a variety of lesion types, with acceptable rates of postoperative complications.

Patient Care: Use of an endoscope for 4th ventricular mass resection demonstrates feasibility for a variety of tumor pathologies. Incorporation of an endoscope in 4th ventricular mass resection may benefit the care of certain patients.

Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the importance of using endoscopy in the resection of 4th ventricular masses 2) Discuss the range of pathologies for which an endoscopic approach would be useful 3) Describe the complications of 4th ventricular tumor resection

References: Austerman, R., Lucas, J., Kammen, A., & Zada, G. (2017). Endoscopic-Assisted Median Aperture Approach for Resection of Fourth Ventricular Tumor and Confirmation of Patency of Cerebral Aqueduct Using an Adjustable-Angle Endoscope: Technical Case Report. Operative Neurosurgery, 13(2), 293-296. Ferguson, S. D., Levine, N. B., Suki, D., Tsung, A. J., Lang, F. F., Sawaya, R., ... & McCutcheon, I. E. (2017). The surgical treatment of tumors of the fourth ventricle: a single-institution experience. Journal of neurosurgery, 1-13.