Erosion of the incus by the chorda tympani nerve in a normally ventilated middle ear and its implications during stapedotomy

Abstract

A case is reported showing partial erosion of the incus long process by the chorda tympani nerve in a normally ventilated middle ear: type A tympanogram, no tympanic membrane retraction, normal middle ear mucosa. A patient with no history of middle ear disease was diagnosed with left otosclerosis. After failed attempt with conservative treatment, she underwent elective stapedotomy. Intraoperatively, a deep groove in the incus long process was found upon mobilization of the chorda tympani without any sign of middle ear inflammation or other ossicular erosion. The tympanic membrane was also normal. Review of the current literature shows cases of incus erosion by the chorda tympani nerve associated with eustachian tube dysfunction resulting in middle ear disease and tympanic membrane retraction. Our findings are unique because unlike previously reported cases, our patient had no history or signs of chronic middle ear disease. Implications of this abnormality on stapedotomy completion are discussed.