2026 Proffered Presentations
S232: TROCHLEAR SCHWANNOMA INTERPOSED BETWEEN THE TWO LEAFLETS OF THE TENTORIUM: AN ILLUSTRATIVE CASE AND SYSTEMATIC REVIEW
Umid Sulaimanov, MD; Umut Tan Sevgi, MD; Benjamin Lee, MD; Ali Riaz; Abdullah Keles, MD; Ufuk Erginoglu, MD; Mustafa Kemal Baskaya, MD; University of Wisconsin Hospital and Clinic
Introduction: Fourth-nerve schwannomas are rare intracranial nerve-sheath tumours, and those that grow between leaflets of the tentorium may pose diagnostic and surgical challenges.
Objective: To detail the microsurgical management of a giant inter-tentorial trochlear schwannoma and, through a systematic review, summarize contemporary presentation patterns, operative strategies, and outcomes.
Method: Following PRISMA guidelines, PubMed and Web of Science were queried on 3 May 2025 for “trochlear nerve” OR “fourth cranial nerve” combined with “schwannoma,” “neurilemmoma,” “neurinoma,” or “nerve sheath tumor.” Human studies containing original clinical data and reporting resection were eligible.
Results:
Case Report: A 22-year-old woman presented with headache and vertigo. MRI revealed a lobulated giant mass with supra- and infratentorial extension. After ventriculo-peritoneal shunt placement, a right-sided paramedian occipital/suboccipital incision was utilized with the patient in prone position. Following resection of the infratentorial component, a tentorial incision enabled advancement into the supratentorial compartment. The tumor, interposed between the two leaflets of the tentorium, was resected in a gross-total fashion. Histopathology confirmed a trochlear schwannoma (WHO Grade I). Postoperatively, the patient remained neurologically intact with no deficits noted.
A total of 45 surgically treated cases were identified. Most patients were middle-aged adults. Double vision and headache were the most common symptoms, and hydrocephalus was frequently observed. Lesions commonly measured 2–3 cm and occasionally traversed the tentorium. The majority were removed gross-totally. New or worsened trochlear palsy was often observed but tended to improve or resolve at follow-up. Other permanent cranial-nerve deficits were uncommon, and no surgery-related mortality was reported.
Conclusion: In cases of tentorial thickening and masses located in the incisura, a trochlear schwannoma growing between the two layers of the tentorium should be considered. Such tumors can be safely removed using a limited tentorial incision with a paramedian supracerebellar infratentorial and transtentorial approach.