Haemangiopericytoma of the trigeminal nerve.

A 41-year-old man presented with a 4-year history of progressive right-sided diplopia on lateral gaze and right nasolabial paraesthesia. A CT revealed minor bone erosion of Meckel's cave and of the right petrous apex by a uniformly enhancing lesion at the base of the skull. Magnetic resonance imaging on three occasions over 2 years showed tumour, measuring 4 cm in diameter, with features suggestive of a trigeminal neuroma. At surgery the lesion had the macroscopic appearance of a giant schwannoma. Histopathological findings were that of a meningeal haemangiopericytoma (HPC) of the trigeminal nerve. Intracranial HPC are rare and aggressive tumours of the central nervous system. They usually arise from the falx, tentorium and dural sinuses. The present case is unique as it originates from a cranial nerve.