Preservation of vestibular nerves in surgery of the cerebellopontine angle: effect on hearing and balance function.

INTRODUCTION

Small tumors of the cerebellopontine angle (CPA) can frequently be removed with preservation of the auditory and the vestibular portion of the eighth cranial nerve. This study was undertaken to estimate the effect of vestibular nerve preservation on both balance and hearing following surgery.

MATERIALS AND METHODS

A retrospective study of all cases of CPA lesions between 1987 and 1991 was undertaken. This identified 11 patients in whom either the superior and/or inferior vestibular nerves were preserved. This included eight acoustic neuromas and three meningiomas. The retrosigmoid approach and total tumor extirpation was undertaken in all cases. Patients undertook a vestibular questionnaire, audiometric testing, and evaluation of vestibulo-ocular responses preoperatively and postoperatively. Additionally, static and dynamic platform posturography was performed postoperatively in 9 of 11 patients.

RESULTS

Follow-up ranged from 6 to 44 months. Of the eight patients with acoustic neuroma, four had a preoperative balance disorder that resolved postoperatively. One patient died of unrelated causes. Of the remaining seven patients with caloric testings, one maintained normal caloric responses. A persistent postoperative phase shift was noted in 4 of the 7 cases with rotatory testing. Three patients were treated for a meningioma. All had a preoperative balance disorder that resolved postoperatively. Two patients showed vestibular response indicative of residual but compromised function on the involved side. The third patient showed absent responses indicating an anatomically intact nerve that does not necessarily predict functional activity. Preservation of the vestibular nerve was associated with preservation of preoperative hearing in five of the patients. This included four of the eight acoustic patients and one of the three meningioma patients.

CONCLUSIONS

Preservation of the vestibular nerve did not result in a chronic balance disorder in this patient population. This study does not allow the authors to conclude if vestibular nerve preservation improves overall hearing after CPA surgery; however, these data suggest that preservation of the inferior vestibular nerve may result in less damage to the cochlear nerve in some patients. Accordingly, preservation of the vestibular nerve in CPA meningioma surgery can be recommended.