Radiographic Estimation of Superior Canal Dehiscence Area in a Prediction Model of Surgical Outcome.

Objective: Computed tomography (CT) imaging of the temporal bone constitutes an integral element in the diagnostic workup of superior canal dehiscence (SCD). This study explores the utility of a clinically efficient method of manually estimating SCD size on CT imaging in predicting surgical outcomes.

Study design: Cohort study.

Setting: Tertiary center.

Methods: Consecutive middle fossa repairs of SCD between 2011 and 2022 were included. Measurements of approximate dehiscence area (ADA), a previously established estimation method, on temporal bone CT imaging were performed by trained raters blind to clinical information. Surgical outcomes, evaluated with symptom resolution and audiometric improvement following repair, were assessed in multivariable regression models with ADA as the primary predictor and patient demographics and other history factors as covariates.

Results: Among 311 cases included, mean ADA was 2.68 mm², and 71% of cases achieved overall symptom improvement (OSI). Every 1 mm² rise in ADA predicted on average 3 dB greater narrowing of low-frequency air-bone gap (β 95% confidence interval, CI [-5.4, -0.7]) but 50% lower odds of OSI (adjusted odds ratio: 95% CI [0.32, 0.78]) among unilateral SCD cases. A model incorporating ADA, patient demographics, and history factors predicted OSI with a sensitivity, specificity combination as high as 85%, 73% and a positive predictive value, negative predictive value combination as high as 85%, 82% (area under the curve: 95% CI: 0.76-0.93).

Conclusion: Increased ADA predicts more pronounced audiometric improvement but poorer symptomatic response among unilateral SCD cases. ADA is an efficient and practical method of estimating SCD size and demonstrated clinical utility in accurately predicting surgical outcomes.