Congenital Aplasia of the External Ear Canal and Total Dehiscence of Mastoid-Tympanic Segment of the Facial Nerve as a Cause of Recurrent Facial Paralysis

Abstract

Facial nerve (FN) macrodehiscence, in contrast to microdehiscence, generally occurs as a result of chronic otitis media and is rarely seen congenitally. A patient with normal hearing who had no history of ear disease or ear operation came to the clinic with recurrent facial paralysis (FP) and frequent blockage of the external ear canal with epithelial debris complaints. In the explorative ear surgery, we observed that the posterior wall of the external ear canal or tympanic ring was absent, a large external ear cavity was covered with a thin skin, the FN was under the skin, and the tympanic-mastoid segment of the FN and chorda tympani extending to the stylomastoid foramen was completely open. FP episodes were associated with the unprotected FN.To prevent an attack of FP, and to self-clean the external ears, mastoid obliteration surgery was performed, and the mastoid segment of the FN was covered with a conchal cartilage graft. This case was diagnosed as congenital aplasia of the external ear canal due to the tympanic bone aplasia-mastoid bone hypoplasia, and the dehiscence of the mastoid-tympanic segment of the FN, and as a cause of recurrent FP, has never to date been identified.