Pre- and postoperative CT appearance of superior semicircular canal dehiscence syndrome.

We report here three cases of patients with superior semicircular canal dehiscence syndrome, prospectively monitored pre- and postoperatively. The computed tomography (CT) examination was performed in 0.6 mm slices with multiplanar reconstructions in the plane of the superior semicircular canal. All the patients also had an audiogram and a vestibular evoked myogenic potentials (VEMP) test. Preoperatively, all the patients had dehiscence of more than 3 mm. Conductive hearing loss for frequencies of less than 1000Hz was present in all cases. The VEMP test showed stimulation thresholds lowered to less than 80dB on the affected side. One case of bilateral involvement in the CT image corresponded to unilateral functional impairment. After plugging surgery, all the patients' auditory and/or vestibular systems were improved. In one case, the reconstruction could not be visualised in CT owing to the radiotransparency of certain materials used in the surgical procedure (wax, fascia, cartilage).