Dimensions of Osseous External Auditory Canal in Otosclerosis Using High-Resolution Computed Tomography

BACKGROUND: There is a general idea that the external auditory canal (EAC) is wide in patients with otosclerosis. However, as far as we know, there is no objective measurement of the EAC of patients with otosclerosis. In this study, we aimed to measure objectively the dimensions of the osseous EAC (OEAC) in otosclerosis, using high-resolution computed tomography (HRCT). METHODS: High-resolution CT images of cranial bones were obtained from 66 patients with otosclerosis and 48 control individuals using a 256- slice CT scanner with a thickness of 0.67 mm. The dimensions and shape of the OEAC from the end of the cartilaginous portion of the EAC to the annulus of the middle ear were then measured. RESULTS: A total of 228 ears were analyzed using CT images. The osseous external ear canal was most commonly conical in both groups. The width of OEAC was not significantly different in the otosclerosis group. The length of the osseous external ear canal was 6.69 ± 1.49 mm in the control group, and 5.96 ± 1.07 mm in the otosclerosis group. It was significantly shorter in the otosclerosis group (P=.001). CONCLUSION: We measured the OEAC in otosclerosis using an objective method. Contrary to what is known, the OEAC tends to be short bilaterally in the ears of patients with otosclerosis, rather than wider.