Operative Injury to the Facial Nerve: Explanations for Its Occurrence During Operations on the Temporal Bone and Suggestions for Its Prevention

Throughout the era characterized by frequent operations for mastoiditis, one of the principal operative hazards was traumatic injury to the endotemporal segment of the cranial VII nerve resulting in temporary or permanent facial paralysis. Now the close anatomical relationship of this nerve to such structures as the oval window and the lateral semicircular canal still expose it to operative trauma because of the frequency with which operative procedures involve these 2 structures. The multidirectional course of the nerve in the temporal bone and its enclosure in a bony canal account for the surgeon's difficulty in identifying the nerve before injuring it; and in the chronically diseased temporal bone, identification of the nerve may be especially difficult because of changes in anatomical relationships secondary to the disease. Cawthorne reviewed 138 cases of intratemporal facial palsy requiring operation. In 47 cases, the palsy resulted from injury, and the most common sites of