Posterior semicircular canal dehiscence: CT prevalence and clinical symptoms.

Objective: To estimate the prevalence of and symptoms associated with posterior semicircular canal dehiscence (PSCD) compared to superior semicircular canal dehiscence (SSCD) and nondehiscent semicircular canals (NDSC).

Methods: Retrospective review. Methods: Academic tertiary referral center. Methods: Review of 412 temporal bone CT scans and associated patient records, excluding patients with prior mastoid or skull base surgery. Methods: CT images (0.625 mm thick) were reviewed in the planes of the semicircular canals. Patient demographics and symptoms were tabulated and analyzed. Methods: Prevalence of PSCD and SSCD; degree of hearing loss; presence or absence of aural fullness, autophony, tinnitus, pulsatile tinnitus, disequilibrium, vertigo, and Tullio phenomenon.

Results: Review of the 412 CT scans revealed 5 cases of PSCD (1.2%) and 20 cases of SSCD (4.9%). All patients with PSCD were male, aged 16 to 73 years. One patient with PSCD reported tinnitus, autophony, disequilibrium, vertigo, and Tullio phenomenon; 2 patients reported only tinnitus and aural fullness, and 1 patient had no symptoms. PSCD was commonly associated with SSCD. There were no significant differences in symptoms between PSCD patients and the other groups. There were, however, statistically significant differences between SSCD patients and NDSC patients in the rates of autophony, tinnitus, and disequilibrium.

Conclusions: The prevalence of PSCD in patients undergoing temporal bone CT scans is considerably less than SSCD (1.2% versus 4.9%), and the 2 conditions commonly coexist. Given the small numbers in our study, we were not able to demonstrate any distinguishable clinical features for the PSCD patients.