Superior semicircular canal dehiscence: congenital or acquired condition?

Background and Purpose: It remains unclear whether SSCD syndrome, characterized by onset of vestibular symptoms in the setting of loud noises, is a congenital or acquired condition. The purpose of this investigation was to assess the prevalence of SSCD on imaging among multiple age groups to determine whether this condition is more likely to be congenital or acquired.
Materials and Methods: Following approval of the institutional review board, 306 consecutive temporal bone CT examinations performed between July 2005 and March 2007 were retrospectively reviewed. Of these, 2 patients were eliminated due to destructive processes in the inner ear. Patients ranged in age from 7 months to 89 years. Images were independently evaluated by 2 neuroradiologists, and the superior semicircular canal was characterized as normal, thin, or frankly dehiscent in each temporal bone. Any discrepancies were resolved by consensus. The patient list was then subcategorized into 5 age groups, and the prevalence of SSCD was calculated for each group.
Results: Twenty-four patients were identified with SSCD, of which 6 demonstrated dehiscence bilaterally. One hundred thirty-seven subjects were identified with thinning, of which 50 demonstrated thinning bilaterally. Each successively older age category experienced a 93% increase (95% CI, 30%-187%) in the prevalence of SSCD (P = .001) and a 9% increase (95% CI, -5%-25%) in the prevalence of thinning (P = .21). Neither crude nor age-adjusted models demonstrated a significant association between thinning and contralateral dehiscence or vice versa.
Conclusions: The increased radiologic prevalence of SSCD among older age groups suggests that this is more commonly an acquired rather than congenital condition.