FACIAL NERVE IN MIDDLE EAR AND MASTOID SURGERY

Abstract

In Reply: We concur with Dr. Eftekharian's comments that experience and good surgical technique are essential to prevent injury to the facial nerve during mastoid surgery. In this study, we attempted to demonstrate that the perineural vascular plexus is a useful landmark for the position of the facial nerve. In order to demonstrate that the vessels may be seen through the bone of an intact facial nerve canal in the horizontal segment, cases found to have a dehiscence of the facial nerve were specifically excluded. There were only two exclusions in this series. This is less than we might usually expect, but, in our experience, the figure of 33% facial nerve dehiscence seems a relatively high incidence. We would agree that a relatively common site of dehiscence is in the region of the “second genu” in the region of the stapes. For this reason the senior authors practice has been to identify the nerve in the horizontal portion well ahead of the second genu. This has the advantage of avoiding the need for early dissection of cholesteatoma in the region of the lateral semicircular canal, where an unsuspected fistula may be encountered. The presence of cholesteatoma or granulations overlying a dehiscent nerve has never presented difficulties. Evacuation of the contents of the cholesteatoma sac often allows the vessels to be identified and careful palpation will confirm whether or not the nerve is dehiscent prior to dissection of the sac from the nerve. It must be admitted that the presence of granulations makes the task more of a challenge but careful and meticulous dissection aided by cotton wool pledgets makes it possible to dissect granulations off a dehiscent facial nerve. The appearance and texture of granulation tissue is quite different to that of the nerve. The use of a facial nerve monitor can be helpful in this context. The authors still contend that the best way to avoid injury is to positively identify the position of the facial nerve at an early stage in the operation. The use of the perineural vascular plexus can be helpful in that it provides a direct, as opposed to an indirect, landmark for the position of the nerve. Vindhi Paleri Carl Watson Department of Otolaryngology-Head and Neck Surgery, Darlington Hospital Darlington, England, U.K.