Superior semicircular canal dehiscence: oblique reformatted CT images for diagnosis

To retrospectively determine, by using thin-section multi-detector row computed tomography (CT), whether additional reformations in the planes of Stenver and Pöschl change the diagnostic interpretation for superior semicircular canal dehiscence (SSCD) when compared with the diagnostic interpretation of standard coronal reformations for SSCD.

Institutional review board approval was obtained, patient anonymity was maintained, and the study was HIPAA compliant. Twenty-seven patients (17 men, 10 women; average age, 45 years; range, 19-72 years) suspected of having SSCD who underwent temporal bone multi-detector row CT were retrospectively identified from electronic medical records. An additional 27 control subjects (nine men, 18 women; average age, 50 years; range, 18-87 years), who underwent temporal bone multi-detector row CT for other reasons, were retrospectively selected from the same period. Two neuroradiologists with certificates of added qualification, one with 5 years and one with 9 years of experience interpreting temporal bone CT images, independently reviewed the 108 temporal bones twice. One review was restricted to transverse images and coronal reformations. The other review used transverse images, coronal reformations, and oblique reformations in the planes of Stenver and Pöschl. The observers were blinded to clinical history, and the two reviews took place 3 months apart to avoid recall bias. The primary outcome measure was the intraobserver discordance rate between the two reviews. kappa Statistics were used to evaluate both intraobserver and interobserver variability.

Observer 1 diagnosed SSCD in 25 of 108 (23%) temporal bones and had no discordances between the two reviews. Observer 2 diagnosed SSCD in 21 of 108 (19%) temporal bones and had one intraobserver discordance. After a post hoc consensus review of this one discordance, the radiologic diagnosis remained equivocal. The discordance involved the right temporal bone of a patient suspected of having SSCD in the left temporal bone, so no clinical follow-up was available.

Coronal reformations from multi-detector row CT of the temporal bone are sufficient for the evaluation of SSCD. Additional reformations in the planes of Stenver and Pöschl do not change the radiologic diagnosis and may be reserved for equivocal or confusing cases.