External Auditory Canal Atresia
(synonyms Congenital aural dysplasia; Microtia)
This 3 year old boy was known to have a hypoplastic left external ear. CT of the temporal bones shows bony atresia of the left external auditory canal (EAC) and a dysplastic auricle, which is typical. Findings in the middle ear are variable, and in this case the handle of the malleus was short or absent. The inner ear and inner auditory canal are typically normal.
The incidence is 1 in 10,000 births and is thought to be due to an in utero insult, with epithelial cells of the first branchial groove failing to split and canalize. The condition may be associated with inherited syndromes such as Crouzon’s, Goldenhar’s or Pierre Robin syndromes where the EAC atresia is bilateral. A normal morphology and location of the stapes is important for surgical reconstruction of ossicular function. EAC atresia may be complicated by congenital cholesteatoma formation behind the atresia plate or in the middle ear.
Reference: Harnsberger, et al. Pocket Radiologist: Head and Neck. Top 100 Diagnoses. Amirsys 2002.
Credit: Dr Bernard Ng, Prince of Wales Hospital, Sydney