Prevalence and classification of posterior semicircular canal dehiscence in HRCTs of the petrous part of the temporal bone : High-resolution computed tomography of posterior semicircular canal dehiscence in combination with conductive or sensorineural hearing loss.

Background And Purpose: The complex anatomy of the petrous part of the temporal bone (or petrous temporal bone) is difficult to understand and constitutes a challenge in the daily diagnostic routine even for experienced neuroradiologists. High-resolution computed tomography (HRCT) is an integral part of equipment-based diagnostics of the rare entity of posterior semicircular canal dehiscence (PSCD). PSCD is characterised by an absence of the bony cover of the posterior semicircular canal in the petrous temporal bone. The aim of this study is to verify the prevalence of PSCD in a group of patients with residual hearing. Furthermore, it is our intention to clarify which location types of dehiscence are possible and which reconstructions are necessary correspondingly.

Study Design And Setting: We evaluated 1370 scans of the petrous part of the temporal bone of patients with residual hearing which were conducted at the participating hospitals of Koblenz, Mainz and Hanover between 2008 and 2016. We verified 37 cases of posterior semicircular canal dehiscence (PSCD). We conducted a sub-group analysis of these 37 HRCT scans including age group correlation and introduced a classification of PSCD.

Results: In 2.7% of the individuals (n = 37), PSCD was detected on at least one side. Furthermore, it was shown that the prevalence of PSCD increases relative to age.

Conclusion: In total, PSCD was detected in 2.7% of the individuals. Posterior dehiscence can be divided into an external and an internal location type. This distinction is crucial for the surgical procedure.