Diagnostic Protocol for Detecting Otosclerosis on High-Resolution Temporal Bone CT

Objectives: To present a systematic checklist to improve diagnosing otosclerosis (OS) on high-resolution computed tomography (HRCT) of the temporal bones and review this protocol's efficacy in diagnosing OS on HRCT. Methods: A retrospective case series was performed at a University Referral Hospital in urban Chicago, Illinois. High-resolution computed tomographies of the temporal bone were reviewed including 17 ears in the test group with surgically confirmed OS and 21 ears in the control group surgically confirmed to not have OS. Preoperative HRCTs were evaluated by a single neuroradiologist using a systematic protocol created to assist in diagnosing OS. This looked for radiolucency at the fissula ante fenestram and pericochlear region, and new bone formation around the oval and round windows. Results: The radiologist accurately diagnosed OS in all 17 test group ears and ruled out OS in all 21 control group ears using the protocol. All 17 test ears were read to have lucency at the fissula ante fenestram, 9 (53.0%) to have new bone formation, and 8 (47.1%) to have cochlear lucency. The radiologist was more confident in diagnosing OS when cochlear lucency was present with the fissula ante fenestram lucency. Conclusions: This HRCT checklist is a highly accurate tool for evaluating the presence of OS when images are reviewed in the systematic fashion described. Imaging prior to surgery aids in counseling patients, preparing surgically, and excluding other pathologies.