Radiologic prevalence of otic capsule dehiscence and development of the Yenigun classification for semicircular canal...

The superior semicircular canal dehiscence is the most well-known otic capsule dehiscence. However, several other dehiscences affect the semicircular canals, cochlea, and vestibule. Our research aimed to examine the frequency, distribution, and correlation between radiologic otic capsule dehiscence in patients exhibiting symptoms of third window syndrome. Additionally, we proposed a new classification system for semicircular canal dehiscence.

In this retrospective study, we included cases who applied to the Otolaryngology Department of our university hospital between January 2015 and September 2023 and underwent standard reformations and Poschl plane CT scans due to symptoms suggestive of third window syndrome. A head and neck radiologist and a general radiologist jointly assessed each CT and decided on measurements.

The study examined 219 patients (438 temporal bones) with suggestive symptoms of third window syndrome. Semicircular Canal Dehiscences were categorized into five types: Type 0 (No dehiscence), Type 1 (Unilateral single canal dehiscence), Type 2 (Bilateral single canal dehiscence), and Type 3 (Unilateral multiple localization dehiscence), and Type 4 (Bilateral multiple localization dehiscence). Semicircular Canal Dehiscence was observed in 71/219 (32,4 %) patients. Type 0:148 (67,6 %), Type1:31(14,2 %), Type2:21(9.6 %), Type 3:15(6.8 %) and Type 4: 4(1.8 %) patients were detected. Cochlear-Facial Dehiscence and Vestibular Aqueduct-Jugular Bulb Dehiscence were seen in 63/219(28,8 %) and 21/219(9,6 %) patients. When cases with Semicircular Canal Dehiscences were examined, Type 2 and Type 4 were seen significantly more frequently than other types in cases with Cochlear-Facial Dehiscence.

When we examine the otic capsule, we see that the possibility of Cochlear-Facial Dehiscence increases in bilateral Semicircular Canal Dehiscence cases. The radiologist should evaluate the otic capsule as a whole. Particular attention should be paid to multiple channels, bilateral localization, cochlear and vestibular dehiscences.