TROCHLEAR NERVE SCHWANNOMAS OCCURRING IN PATIENTS WITHOUT NEUROFIBROMATOSIS - CASE-REPORT AND REVIEW OF THE LITERATURE

OBJECTIVE AND IMPORTANCE: Despite their predilection for sensory nerve s, intracranial schwannomas have been reported in a number of mixed an d purely motor cranial nerves, especially in association with Type 2 n eurofibromatosis. We report the rare occurrence of a trochlear nerve s chwannoma in a patient without neurofibromatosis and review 17 other c ase reports from the literature. CLINICAL PRESENTATION: A 35-year-old woman presented with an 8-week history of evolving left hemiparesis, b ilateral bulbar paresis, and out-of-character emotional lability. INTE RVENTION: She underwent a left temporal craniotomy and a subtemporal, transtentorial approach to the tentorial hiatus, with complete excisio n of a cisternal trochlear nerve schwannoma. CONCLUSION: Postoperative complications included temporary oculomotor and abducens nerve palsie s and temporary right hemiparesis and mild expressive dysphasia, which were resolved at 23-month follow-up. Preoperative symptoms and signs completely resolved, but a postoperative complete trochlear nerve pals y required inferior oblique myectomy for correction of diplopia. A rev iew of the literature showed no preoperative trochlear nerve involveme nt in at least 45% of cases. The tumor is isointense on T1- and T2-wei ghted magnetic resonance images and enhances brightly with gadolinium. The most frequently used approach for surgical excision is the subtem poral approach, and the tumor is almost always totally excised. Long-t erm follow-up suggests recovery of preoperative deficit, and persistin g or new trochlear nerve palsy is the rule.