Magnetic resonance imaging and computed tomography for diagnosing semicircular canal dehiscence

We investigated the semicircular canal (SC) dehiscence using temporal computed tomography (CT) and magnetic resonance (MR) imaging.

We retrospectively reviewed 114 (228 ears) consecutive MR images and CT scans of the temporal bones for dehiscence of the SCs. In the 1.5 Tesla (T) MR imaging, T1 and T2-weighted images were obtained. Dehiscence of the SCs was defined by absence of high attenuation bone coverage on the CT scans, and absence of low-signal bone margins on the MR images.

Superior SC dehiscence was detected in 4 (1.8%) ears using CT scans and 5 (2.2%) ears using MR imaging. Posterior SC dehiscence was detected in 4 (1.8%) ears using CT scans and 4 (1.8%) ears using MR imaging. In the non-dehiscent cases, there was hypointense bone coverage between the canal and the cerebrospinal fluid (CSF). However, in the cases of semicircular canal dehiscence, hypointense bone tissue did not appear between the canal and the CSF in the MR imaging.

If there is clinical doubt about the presence of SC dehiscence, we recommend that MR imaging be conducted first. When dehiscence is not seen in the MR, a CT examination should be performed. MR imaging is preferred primarily, because it does not contain ionizing radiation.