Vestibular Neurectomy and Microvascular Decompression

Meniere's disease is typically characterized by the classic symptomatological triad consisting of vertigo associated with nausea and vomiting, fluctuating but progressive hearing loss, and tinnitus. Aural fullness is also a frequent symptom. The main pathophysiological substrate of Meniere's disease is certainly endolymphatic hydrops, the etiology of which is probably multifactorial, but still not completely understood. Poor knowledge ofthe causes of Meniere's disease has given rise to a number of medical and surgical treatments that almost invariably treat symptoms. Vestibular neurectomy (VN) is to date the surgical treatment of choice in Meniere's disease, with success rates for vertigo ranging from 85 to 100%. 1-8 Postoperative auditory results, however, are somewhat unpredictable. Improvement in hearing, tinnitus, and aural fullness have been reported by some authors, without any convincing explanation regarding the causes of this phenomenon. Microvascular decompression (MVD) of cranial nerve VIII in Meniere's disease and disabling positional vertigo was proposed by McCabe and Harker9 and by M0ller,10 based on the frequent presence of a vascular loop in contact with the VIIth nerve in these patients. We have personally observed and reported contact between the anterior or posterior inferior cerebellar arteries (AICA, PICA) and the VIIIth nerve in seven consecutive VNs performed in subjects with Meniere's disease."I The ultrastructural evaluation of the removed portion of the vestibular nerve always showed severe alterations in the central portion of the nerve (ie, degeneration of the axons with altered myelin sheaths, proliferation of the astrocyte processes, and numerous spherical bodies), which were probably the consequence of the vascular cross-compression. In the series reported on by McCabe and Harker9 and M0ller'0 vertigo improved in 72 to 100% of subjects with Meniere's disease who had undergone MVD. Improvement in hearing was found in 0 to 22%. The findings in the literature and our own personal data prompted us to perform an accurate exploration of the cerebellopontine angle (CPA) in each subject with Me-