Hemorrhagic intracranial inflammatory pseudotumor originating from the trigeminal nerve: a case report.

We report here on a case of intracranial inflammatory pseudotumor arising from the trigeminal nerve. A 52-year-old man presented with sudden onset severe headache. He had had facial numbness several months earlier and no signs indicating infection. On the computerized tomography scan, intracranial hemorrhage was detected at the cerebellopontine angle. Magnetic resonance imaging demonstrated a 2.7-cm-sized, homogenously enhancing mass. A provisional diagnosis of trigeminal schwannoma was made, and suboccipital craniotomy was then performed. The mass was encapsulated and had multiple capsular veins. There was a evidence of intratumoral bleeding. It originated from the trigeminal root and was adhered to the 4th cranial nerve. Pathologic examination showed fibrovascular tissue with dense infiltrates of plasma cells and lymphocytes, some histiocytes, and occasional neutrophils and eosinophils. It showed immunopositivity for leukocyte common antigen (LCA) and immunonegativity for S-100 and lysozyme. It was also immunopositive for EBV antigen. Intracranial inflammatory pseudotumors mostly arise from dural/meningeal structures in the intracranial location. This case is the first to describe an intracranial inflammatory pseudotumor originating from a cranial nerve. The pathologic examination supported the postinfection hypothesis out of several possible pathologic mechanisms.