High-resolution computed tomography of isolated congenital anomalies of the stapes: a pictural review using oblique multiplanar reformation in the "axial stapes" plane.

Purpose: Isolated congenital anomalies of the stapes are infrequent but highly variable. The goal of this study is to present the numerous observed anomalies based on a large number of cases, and to describe anatomical variations and malformations of the stapes using high-resolution computed tomography (CT), after proper reorientation in the "axial stapes" plane.

Materials And Methods: The 1805 CT of temporal bones performed during the past 5 years have been retrospectively studied. After reconstructing the images in the stapes axial plane, the ears presenting a congenital anomaly of the stapes were included in this study. All the ears with acquired lesions were excluded. The anomalies have been sorted according to the affected part of the stapes: the superstructure, the footplate or the obturator foramen. Two neuroradiologists classified the anomalies as either anatomical variation, malformation, or undetermined.

Results: Sixty-one stapes in 47 patients were found to have one or more congenitally abnormal shapes (bilateral anomalies were found in 14 of these patients). The abnormal part of the stapes was the superstructure in 17 cases, the footplate in 13 cases, the obturator foramen in 19 cases (with a high frequency of "double stapes" shape) while in 12 cases multiple parts were affected.

Conclusion: The use of ossicle reconstructions in the "axial stapes" plane with current multislice CT allows analyzing even minor congenital anomalies of the stapes. The boundaries between normal variations and malformations are sometimes difficult to set, especially when anomalies are minor. Malformations are more easily diagnosed when multiple parts of the stapes are affected.