The extent of inferior displacement of the mastoid tegmen is related to the severity of congenital aural atresia.

Conclusion: The extent of inferior displacement of the mastoid tegmen is related to the severity of congenital aural atresia (CAA).

Objective: To analyze anatomic variations observed on high-resolution temporal bone computed tomography (TBCT) in patients with CAA, the extent of inferior displacement of the mastoid tegmen and the size of the incudo-stapedial (IS) joint angle were compared with surgical parameters for atresiaplasty, such as Jahrsdoerfer score and hearing acuity.

Methods: Sixty-one patients with unilateral CAA underwent high-resolution TBCT and hearing tests. We evaluated TBCTs in terms of Jahrsdoerfer criteria and analyzed the relationships among the inferior displacement of the mastoid tegmen, size of the IS joint angle, hearing acuity, and the Jahrsdoerfer score on the atretic side.

Results: IS joint angle on the atretic side was found to be 120.6 ± 11°, which was significantly greater than the corresponding value of 103.4 ± 5.4° on the normal side. Cholesteatoma occurred significantly more often in CAA patients with narrow external auditory canals (EACs) (9/27; 33.3%), compared with CAA patients with no EAC opening (2/34; 5.9%). There was a significant relation between the extent of inferior displacement of the mastoid tegmen (28.9% in the atretic side and 17.3% in the normal side) and the Jahrsdoerfer score (p < 0.0001).