Exposure of the facial nerve within the facial canal

Abstract

BACKGROUND : The facial canal lies in the petrous part of the temporal bone and contains the facial nerve. The facial canal and nerve are divided into three segments: the labyrinthine, tympanic and mastoid segments, which travel in different planes. These segments are closely related to the structures of the middle- and inner-ear, so pathology of the intracranial facial nerve is often evident in cochlear implant users. The facial canal and nerve are of great concern to otologists during electrode placement for a cochlear implant, as any damage to the nerve may result in untreatable facial paralysis. Few studies have been conducted on a cadaveric population, with most carried out on CT images of the cochlea and facial nerve. Thus, there is no standard or straightforward methodology to visualise the facial canal and nerve directly. We propose a detailed dissection technique to bridge this gap in research. METHOD : Four cadavers were used, and both the left and right facial canals were dissected. After the exposure of the cranial floor, the internal acoustic meatus and the facial canal were dissected out using drilling tools to remove the surrounding temporal bone and expose the facial nerve within the facial canal. RESULTS : This technique allowed for morphometric analyses and observations of the facial canal in relation to the middle- and inner-ear. CONCLUSION : Knowledge of the facial canal may assist otosurgeons in safely dissecting the region without injuring vital structures within this area.