Outcomes of Radiologist Recommendations for Temporal Bone CT to Assess Superior Semicircular Canal Dehiscence on Temporal Bone MRI

BACKGROUND AND PURPOSE: Superior semicircular canal dehiscence can be detected on temporal bone MR images. Radiologists often recommend confirmation with temporal bone CT due to reported lower MRI positive predictive value. The value of these recommendations is unclear given that CT overestimates dehiscence due to volume averaging and that only a small proportion of patients with dehiscence on CT suffer from dehiscence syndrome. We thus evaluated final diagnoses and outcomes in patients who adhered to the recommended additional CT.

MATERIALS AND METHODS: This retrospective cohort observational study, performed at a multi-institution healthcare system, included consecutive temporal bone MRI reports 6/1/2021-5/31/2022 with a recommendation for additional temporal bone CT. We recorded: whether CT was performed, dehiscence present on CT, symptoms, final diagnosis, treatment decisions, and outcomes. Actionability elements (complete containing imaging modality, time frame, and rationale; unambiguous; unconditional; without multiplicity; and without alternate language) of the recommendations were extracted from a prior data set. Descriptive statistics were performed. A binomial generalized linear model was used to test the correlation of ambiguous recommendation language with recommendation adherence.

RESULTS: Summarize actual data. 5109 temporal bone MRI examinations were performed and interpreted by 34 radiologists. 187/5109 reports (3.7%) included a recommendation for additional temporal bone CT including 101/5109 (2.0%) specifically for suspected superior semicircular canal dehiscence. While 22% (22/101) of these recommended examinations were performed, only 32% of these (7/22) confirmed dehiscence. Ultimately, only 1 patient was diagnosed with dehiscence syndrome and was managed conservatively. No recommendations for additional imaging (0/101) met actionable criteria and 76.2% (77/101) were ambiguous. Ambiguous recommendations had 0.54 lower, but not statistically significant, odds of being performed (95% CI: 0.19-1.6, p=0.25).

CONCLUSIONS: Radiologist recommendations for temporal bone CT in the setting of questionable superior semicircular canal dehiscence findings on MRI appear to have negligible clinical value and thus it is likely most appropriate to report possible SSCD in the MRI report impression without recommending further imaging.

ABBREVIATIONS: SSCD= superior semicircular canal dehiscence.