Aural atresia, congenital
A rare anomaly of the ear that involves some degree of failure of the development of the external auditory canal. The malformation can also involve the tympanic membrane, ossicles and middle ear space. The inner ear development is most often normal. Different CAA forms are known. CAA type I is characterized by bony or fibrous atresia of the lateral part of the external auditory canal and an almost normal medial part and middle ear. CAA type II is the most frequent type and is characterized by partial or total aplasia of the external auditory canal. CAA type IIA involves an external auditory canal with either complete bony atresia of the medial part or partial aplasia that ends blindly in a fistula leading to a rudimentary tympanic membrane. CAA type IIB is characterized by bony stenosis of the total length of the external auditory canal. CAA type III involves bony atresia of the external auditory canal and a very small or absent middle-ear cavity.
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