Embryology and Epidemiology

The incidence of congenital aural atresia is 1:10,000 to 20,000.3 Unilateral atresia is five to six times more common.1 The embryologic basis of aural atresia is the failure of the external auditory canal to recanalize during the sixth and seventh months of gestation. The external auditory canal is derived from the first branchial groove. In the developing embryo, an epithelial core of cells arises and fills the external auditory canal. It is the failure of these cells to canalize that gives rise to aural atresia. Aural atresia occurs either together with, or in isolation from, external or middle ear malformations. It is important to note that middle ear malformations are much more common in the atretic ear where there is also microtia present; they are also more common in the normal ear where the other ear canal is atretic than if there are two normal ears.1

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