Computed tomography of the auditory ossicles

High resolution CT has become an important tool of radiographic assessment of the temporal bone. This study was undertaken to establish criteria for spatial relationship of the ossicles on axial projection. Normal CT of the fifty-seven temporal bones was reviewed. All parts of the malleus and incus were identified in all cases, while the head, the anterior crus and the posterior crus of the stapes were identified in 68.4 % (39/57), 5.3 % (3/57), 3.5 % (2/57), respectively. In none of the cases was the footplate of the stapes seen. The malleus manubrium and the incus long process aligned almost parallel to each other with being 28.00 (S.D. 6.50) and 26.90 (S.D. 5.70) to the coronal plane, respectively. The malleus head and the incus body and short process lied within the attic on the 28.00 (S.D. 3.90) angle to the sagittal plane. With the above-mentioned knowledge of the normal spatial alignment of the ossicles, one is able to detect subtle malalignment of the ossicular chain on axial CT alone. However, it should be kept in mind that coronal CT would usually be necessary to evaluate the incudostapedial joint as well as the stapes itself. Pathologic cases involving the ossicles were illustrated. (author)