Superior semicircular canal dehiscence: prevalence in a population with clinical suspected otosclerosis-type hearing loss

Key-words. Superior semicircular canal; dehiscence; otosclerosis; stapes fixation; mixed hearing loss Abstract. Superior semicircular canal dehiscence: prevalence in a population with clinical suspected otosclerosis-type hearing loss. Superior semicircular canal dehiscence (SSCD) can present with a variety of symptoms that can be pre - dominantly auditory, predominantly vestibular or both. It can mimic a wide range of otological disorders, in particular otosclerosis-like stapes fixation. Our study revealed that, in 5.3% of our patients with clinically suspected otosclerosis, SSCD was detected in high-resolution multi-detector computed tomography (HRMDCT) of the temporal bone. We therefore emphasise the value of HRMDCT with reconstructions in the plane of the superior semicircular canal and per - pendicular to the superior semicircular canal in the diagnostic work-up of each patient with a tentative diagnosis of otosclerosis-type stapes fixation. Where there are doubts, VEMP testing should be performed. We believe that a number of unexplained complications after an uneventful stapedotomy procedure might be explained by a pre-operatively undetected dehiscent superior semicircular canal and therefore unwarranted surgery. The typical feature of the conductive hearing loss due to SSCD compared to otosclerosis is an air-bone gap which is much more prominent at low frequencies than at high frequencies.