Hemangiopericytoma of the Cerebellopontine Angle: A Wolf in Sheep's Clothing.

Primary meningeal hemangiopericytoma (HPC) is a rare, aggressive dura based tumor that remarkably mimics a meningioma clinically and radiologically. Its occurrence within the cerebellopontine angle (CPA) is exceptional, and establishing the exact diagnosis is of the utmost importance since total resection remains the cornerstone of treatment. A 42-year-old man presented with a three-month history of progressively worsening vertigo and difficulty in walking. On admission, his neurological examination revealed a right peripheral facial palsy, right abducens palsy and left hemiparesis, suggesting the diagnosis of Millard-Gubler syndrome. Computed tomography and magnetic resonance imaging demonstrated a homogeneously enhancing dura based lesion of the right CPA causing major brain stem compression. There was no widening of the ipsilateral internal auditory canal. A standard retrosigmoid craniotomy was performed to access the right CPA. Exposure of the lesion revealed a well-encapsulated, gray, fibrous lesion, which appeared to originate from the tentorium. Gross total resection was achieved and confirmed radiologically. The microscopic features and the immunohistochemical profile confirmed the diagnosis of a HPC, and adjuvant radiation therapy was administered. Ten years later, the patient presented with a severe neurological deficit due to a local recurrence, but at that time refused any second intervention. He died three months later. HPC can locate within the CPA and present as a Millard-Gubler syndrome. The diagnosis should be kept in mind in case of a CPA dura based tumor. Radical surgery plus radiation therapy can maximize the recurrence-free survival and close follow-up remains mandatory to spot recurrences early.