Twelve patients underwent microvascular decompression by retrosigmoid approach to relieve severe hemifacial spasm. The surgery was done under intraoperative monitoring of the auditory function. Assessment at Day 2, Day 10, 2 months and 6 months after the operation found that the surgery had resulted in 9 recoveries, 3 improvements and 1 failure. Brain stem auditory evoked potentials monitoring showed that the interposition of Teflon between the vascular loop and the facial nerve is a critical stage for the auditory function. Six of the twelve patients were also complaining of cochleo-vestibular disorders: vertigo and tinnitus, or hearing loss and tinnitus, or vertigo alone. The surgery improved at least one of these cochleo-vestibular symptoms in each one of the patients. There was one hearing improvement, vertigo disappeared in three cases out of four, and tinnitus disappeared in four cases out of five. The possibility of a concomitant compression of cochleo-vestibular and facial nerve was investigated using cochleovestibular tests, radiological data and intra-operative findings.