Three dimensional CT imagings of bony anomaly along the chorda tympani before and after hearing reconstructive surgery

Abstract

A case of rare middle ear anomaly is presented. Five year old boy had a congenital hearing impairment of the left ear. His audiogram was 68 dB in an average of the left air conduction hearing and the right ear was normal. He had normal ear drum with a relatively narrow external acoustic meatus and small pinna. He was diagnosed as middle ear anomaly and operated on September 2006.
Three dimensional (3D) CT before the surgery showed a bony bridge along the chorda tympani in the left ear and normal structure in the right. Operative findings was identical with 3D CT. A bone bridge fixed the malleus and ossicular mobility became smooth after drilling the bone. Other anomaly was not seen in the middle ear cleft. His left hearing has improved up to 30 dB. 3D CT after the surgery showed normal ossicular chain and disappearance of the abnormal bone.
Middle ear anomaly has a variety of findings and no typical common pattern. This kind of bone anomaly has rarely been reported and so it was an unexpected operative finding. However, 3D CT is very useful to detect such a rare anomaly and its imaging information can help ear surgeon to perform a safe operation.