[Sonomotor vestibular reflex in acoustic neuroma]

Despite recent advance in diagnosis and surgical techniques of acoustic neuroma, ideal criteria for hearing preservation attempt remain unsatisfactory. This study reports sonomotor vestibular reflex recorded pre and postoperatively in 20 patients with acoustic neuroma. Hearing preservation was attempted according to tumor size and preoperative pure tone audiometry results. The studied population was divided in 2 groups according to hearing preservation was attempted (group 1 n = 13, retrosigmoid approach) or not (group 2 n = 7, translabyrinthin approach). In accordance with postsurgical audition, the subjects of group 1 were distributed in group 1-A (postsurgical preserved audition n = 4) or group 1-B (postsurgical unpreserved audition n = 9). Presurgical sonomotor vestibular reflex in response to pathological stimulation were compared in the different groups. In preoperative period, sonomotor vertibular reflex in response to pathological side stimulation were present in all the patients of group 1-A with a similar amplitude to those obtained when stimulating healthy side. In 6 subjects of group 1-B these responses were present but with a smaller amplitude than those obtained when stimulating healthy side. The responses were absent in 3 subjects of group 1-B and in all the subjects of the group 2. These result tend to demonstrate that preoperative presence of sonomotor vestibular reflex in response to neuroma side stimulation with amplitude similar to those obtained by healthy side stimulation is a favorable criterion for hearing preservation attempt. On the opposite, the decrease in the amplitude of these responses or their absence seems to be unfavorable for hearing preservation attempt.(ABSTRACT TRUNCATED AT 250 WORDS)