[Case of tinnitus, vertigo, and a loss of caloric response due to neurovascular compression].

The authors report a case of neurovascular compression of the eighth cranial nerve in a 49-year-old businessman. The patient was admitted to the University of Tokyo Hospital because of progressive vertigo and tinnitus on the right without hearing loss over the seven years prior. There were no other symptoms. The general examination was normal. He was neurologically intact except for loss of caloric response. Audiometric studies and brain stem response were normal. The findings of routine hematology, biochemistry, and serology were within normal limits. Tomogram showed that right internal auditory meatus was wider than the left by 2 mm. Computed tomography with metrizamide demonstrated a filling defect in the right cerebellopontine angle. We decided to proceed with exploratory operation with the tentative diagnosis of a left cerebello-pontine angle mass, perhaps neurinoma en plaque meningioma, or epidermoid tumor. Left retromastoid craniectomy with microsurgical exploration of the cerebellopontine angle revealed not a tumor, but a loop of the anterior interior cerebellar artery (AICA) compressing the eighth cranial nerve close to the porus acousticus. A piece of muscle was inserted between the eighth cranial nerve and the AICA. His postoperative course was uneventfull with complete relief of symptoms and without impairment of hearing. In patients with hemifacial spasm and trigeminal neuralgia, neurovascular compression (NVC) has been found at the root entry zone of the facial or trigeminal nerves close to the brain stem at the "junction zone" on the glia and schwann sheath of these nerves.(ABSTRACT TRUNCATED AT 250 WORDS)