Vascular compression of the eighth cranial nerve as a cause of vertigo

Some patients have vertigo that is more or less constant, associated with varying degrees of nausea, and only relieved by bedrest. This disorder, named disabling positional vertigo (DPV), was found to be caused by a blood vessel or vessels compressing the eighth cranial nerve in its intracranial portion, and it can be relieved by microvascular decompression (MVD) of the nerve. Important in the differential diagnosis of DPV are a detailed history, the results of audiometry (10 to 15 dB interaural threshold difference or a small mid-frequency notch), acoustic middle ear reflex response testing (may be abnormal), and recordings of brainstem auditory evoked potentials (BAEP). BAEP in such cases show increased conduction time in the auditory nerve and/or prolonged latency of wave V recorded from the contralateral ear, possibly the result of brainstem compression. Abnormalities on vestibular testing often do not reflect the severity of the illness. Forty-one patients who underwent MVD to treat DPV in one year at the author's institution have been followed for 4.5 to 5.5 years. By self-evaluation, 20 had excellent and 10 good results of the operation. The success of this procedure is even higher today, since it was found that very small blood vessels, including veins, can cause DPV; thus all vessels touching the nerve are now managed. Complications of MVD are rare. The most frequent, hearing loss, occurred in only one patient in this series.