Rethinking Semicircular Canal Dehiscence
Although posterior and superior canal dehiscence has been associated with vertigo, and/or dizziness, and/or low-frequency conductive hearing loss, often these associations/observations have been made after a symptomatic patient presents and high resolution CT scans are executed. Indeed, atypical CT findings are sometimes reported and consequently, the signs and symptoms which brought the patient in are then attributed to the atypical CT findings (for more information, see Chi et al, 2009; and Rosowski, 2012). However, the issue as to the natural occurrence/prevalence of canal dehiscence has rarely been studied in-depth.
Meiklejohn and colleagues (2015) report their retrospective and histopathologic study of children under age 7 years, including 228 high resolution CT scans and 58 temporal bone specimens. Their work revealed “radiographic dehiscence of the canals is common in the first 6 months of life…” and the bone overlying the canals increases in thickness as the child ages. The authors note congenital and acquired hypothesis for the origin of dehiscence have been reported. They state “radiographic dehiscence is commonly seen in CT scans of very young children….” Further, they state that “the overall data therefore support…and suggest that radiographic dehiscence seen in early life may be an artifact that resolves across time…” as the bone around the canals thickens. Meiklejohn et al conclude that “the lack of associated symptoms in our population also suggests that such radiographic findings rarely have clinical significance...” and clinicians should be cautious when they make the diagnosis of canal dehiscence in young children.
For More Information, References, and Recommendations
Chi FL, Ren DD, Dai CF. (2009) Variety of Audiologic Manifestations in Patients with Superior Semicircular Canal Dehiscence. Otology & Neurotology 31(1):2-10.
Meiklejohn DA, Corrales CE, Boldt BM, Sharon JD, Yeom KW, Carey JP, Blevins NH. (2015) Pediatric Semicircular Canal Dehiscence: Radiographic and Histologic Prevalence, with Clinical Correlation. Otology & Neurotology 36:1383-1389.
Rosowski J. (2012) Peripheral Anatomy and Physiology- Outer and Middle Ear. In Translational Perspectives in Auditory Neuroscience. Editors: Kelly L. Tremblay and Robert. F. Burkard. Published by Plural Publishing.