Presigmoid transpetrosal approach for the treatment of a large trochlear nerve schwannoma--case report.

A 61-year-old man presented with a rare, large trochlear nerve schwannoma manifesting as left-sided weakness and hypesthesia, bilateral bulbar pareses, and trochlear nerve paresis persisting for 3 months. T1-weighted magnetic resonance imaging with gadolinium revealed an intensely enhanced, well-circumscribed lesion with multicystic formation occupying the prepontine and interpeduncular cisterns and compressing the pons and midbrain with greater extension to the right. The mass was completely removed through the presigmoid transpetrosal approach with preservation of the posterior cerebral, superior cerebellar, and basilar arteries and their branches. Neuroradiological examination after 3 years demonstrated no recurrence. Enlargement of a tumor in the cisternal portion is inclined to involve and/or encase the adjacent major arteries and their branches. The presigmoid transpetrosal approach is one of the best surgical routes to remove a large trochlear nerve schwannoma safely and completely.