Arachnoid cyst of the cerebellopontine angle associated with gliosis of the eighth cranial nerve.

The clinical syndrome produced by a cyst in the cerebellopontine angle (CPA) may closely mimic that of an acoustic neuroma, with sensorineural hearing loss, impaired corneal reflex, and cerebellar signs with increased intracranial pressure. Facial palsy is seldom reported. Gliosis of the eighth nerve is common but its association with CPA arachnoid cyst is very rare and not previously reported. We report a patient with a CPA arachnoid cyst associated with gliosis of the eighth cranial nerve. He presented with right peripheral facial palsy, and gliosis of the eighth nerve was diagnosed intraoperatively. CPA arachnoid cysts should be included in the differential diagnosis of peripheral facial palsy and the eighth cranial nerve should be examined during the resection and fenestration of the arachnoid cyst.