Otosclerosis: anatomy and pathology in the temporal bone assessed by multi-slice and cone-beam CT

To assess the use of cone beam computed tomography (CBCT) compared with multi-slice computed tomography (MSCT) in otosclerosis, with special emphasis on middle- and inner-ear anatomy.

Prospective study.

Twenty patients who underwent a stapedectomy 30 years ago were selected on the basis of bone conduction threshold values. Their mean age was 65 years (range, 48-76 yr).

All patients underwent CBCT and MSCT with a slice thickness of 0.5 to 0.6 mm.

Sixteen middle- and inner-ear anatomic structures and stapedial prostheses were analyzed by visual grading analysis. To assess critical reproduction and thereby the clinical applicability of CBCT, a dichotomization was made. Assessment of otosclerotic foci was performed using a grading system dividing the lesions in; (1) sole fenestral lesions, (2) retrofenestral lesions with or without fenestral lesions and (3) severe retrofenestral lesions.

The 16 anatomic structures were clearly reproduced by both imaging techniques. However, there was an interobserver variation in judging the superiority of 1 method in favor of the other. Otosclerotic lesions were diagnosed in 80/95% using MSCT and 50/85% using CBCT (evaluators 1 and 2, respectively). Retrofenestral lesions were diagnosed in 5 of 10 of ears with severe-to-profound hearing loss, whereas no retrofenestral lesions were diagnosed in the 10 ears with mild-to-moderate hearing loss. The stapedial prostheses were adequately or very well reproduced by both methods.

CBCT is a new imaging technique with a considerably lower radiation dose than conventional MSCT. Our study indicates that CBCT is suitable and, in many ways, equivalent to MSCT, for temporal bone imaging in otosclerosis.