[Computed tomography findings in middle ear anomaly]

The efficacy of computed tomography (CT) of the temporal bone was studied in 45 ears with a middle ear anomaly but whose tympanic membranes were normal. The plane of the film was 30 degrees oblique to the orbito-meatal line. Four otorhinolaryngologists made radiological diagnoses of the CT film without having any information about the patients. CT films of 40 normal ears were also evaluated and served as controls. The incudo-stapedial joint (I-S joint) and the stapes were visualized in all control group subjects. The percentage of correct diagnoses was 77.8% for separation of the I-S joint, and 75.6% for fixation of the stapes. The monopedal stapes was not visualized. Fixation of the malleus and the incus could not be diagnosed correctly. Abnormalities in the location of the facial nerve were visualized in a few ears. CT of the temporal bone was clinically useful for differentiating I-S joint separation and fixation of the stapes.