Prevalence of radiologic superior canal dehiscence in normal ears and ears with chronic otitis media.

Objectives/hypothesis: Although labyrinth fistulae are caused mostly by cholesteatoma, they can occur in long-standing chronic otitis media (COM) without cholesteatoma. We aimed to compare the prevalence of radiologic SCD on computed tomography (CT) between normal ears and contralateral COM ears in patients with unilateral COM and to assess the prevalence of superior canal dehiscence (SCD) according to the age.

Study Design: Case series with comparison performed at a tertiary care academic referral center.

Methods: We retrospectively reviewed consecutive temporal bone CT scans of 759 patients with unilateral COM between 2009 and 2011. The mean (± standard deviation) age was 48 years (±14 years). Images were independently evaluated by two otologists, and the bone overlying the superior canal was characterized as normal, suspicious, or definite SCD.

Results: The prevalence (3.4%) of definite SCD in COM ears was significantly higher than that (0.3%) in normal ears. The prevalence (6.6%) of suspicious or definite SCD in COM ears was also higher than that (1.2%) in normal ears. There was no correlation between the prevalence of SCD and age in either normal or COM ears. All of the normal ears with suspicious or definite SCD also showed contralateral suspicious or definite SCD (bilateral involvement).

Conclusions: Our present findings suggest that the COM is related to the presence of SCD. The roof of the temporal bone may become thin by the failure of postnatal bone development and susceptible to chronic brain pulsation and pressure exerted by the temporal lobe in COM ears.