Computed tomography approximated superior semicircular canal dehiscence size and location and their association with clinical presentation

Objective: This study investigates the relationship of superior semicircular canal dehiscence (SSCD) size and location with patient symptomatology and audiometry.

Methods: We retrospectively reviewed SSCD cases presented to a tertiary institution between 2011 and 2022. Dehiscence length and width measured on high-resolution temporal bone computed tomography imaging were used to calculate an approximate dehiscence area (ADA). Dehiscence location was classified employing a six-grade system. Multivariable regression analyses were performed with symptomatology and audiogram metrics as outcome variables and ADA and dehiscence location as the primary covariates of interest.

Results: A total of 402 SSCD were included in the analysis. Controlling for patient age, sex, dehiscence laterality, and location, greater ADA was independently associated higher rates of autophony (aOR 1.39; 95% C.I. 1.14-1.71; P = 0.004) and hyper-amplification (aOR 1.39; 1.14-1.70; P = 0.004). Additionally, dehiscences with greater ADA exhibited significantly lower bone conduction threshold at 500 Hz (adjusted β -1.75, P = 0.006) and 1000 Hz (adjusted β -1.61, P = 0.018) and significantly wider air-bone gap at 500 Hz (adjusted β 2.22, P < 0.001) and 1000 Hz (adjusted β 1.00, P = 0.039). Dehiscence location was not independently associated with any outcome variable examined when accounting for dehiscence size.

Conclusion: The size of dehiscence is more independently related to clinical presentations than the anatomical location of the dehiscence in the superior semicircular canal. Greater dehiscence size is associated with symptomatology and audiometry consistent with more severe bone conduction hyperacusis.