Giant Trigeminal Schwannoma Presenting with Obstructive Hydrocephalus.

Trigeminal schwannomas represent between 0.07% and 0.36% of all intracranial tumors and 0.8% to 8% of intracranial schwannomas. Selection of the appropriate management strategy requires an understanding of the tumor's natural history and treatment outcomes. This report describes the case of a 36-year-old male who presented with a three-month history of progressive headaches, dizziness, loss of balance, decreased sleep, and cognitive decline. Magnetic resonance imaging revealed a large enhancing lesion centered around the left Meckel's cave and extending into both the middle and the posterior fossa with obstructive hydrocephalus secondary to compression of the fourth ventricle. Resection of the posterior fossa component of the tumor was performed in order to relieve the mass effect upon the brainstem without attempting a radical removal of the middle fossa component and a potential risk of further cognitive impairment. The pathological exam confirmed the diagnosis of a trigeminal schwannoma. The residual tumor showed progressive spontaneous volumetric shrinkage after a subtotal surgical resection. This case shows the value of a planned conservative surgery in complex schwannomas and highlights the challenges in interpreting the treatment responses in these benign tumors, whether approached surgically or with stereotactic radiation techniques.