The facial nerve in congenital middle ear malformations

The two most common anomalies of the facial nerve encountered in patients with a congenital malformation of the middle ear are displacement of the nerve and lack of a bony cover, two conditions that place the nerve at risk of being injured by the unwary surgeon. Malformations of the stapes are often found in association with facial nerve anomalies and may range from underdevelopment to complete absence. A congenital absence of the oval window is not uncommon. The position of the facial nerve in relation to the location and maturation of the ossicles will determine the method of ossicular chain repair. Creation of a new oval window by drilling may require the surgeon to purposely displace the facial nerve to ensure a more direct alignment of the prosthesis with the vestibule. Any part of the incus or malleus may be contoured by drilling to accommodate the loop end of the wire-piston prosthesis. An aberrant course of the facial nerve was found in 13/54 (24%) ears having a congenital malformation of the middle ear. All 54 ears had a patent external ear canal and an identifiable tympanic membrane. Patients with atresia or stenosis of the external ear canal were specifically excluded from this study.