Radiologic Evaluation of the Round Window Niche Configuration: A One-Stop Approach

BACKGROUND: Preoperative radiological prediction of the round window niche configuration. METHODS: Fifty patients were evaluated. A single-axial high-resolution computed tomography image at the level of the cochlear aqueduct was compared to the intraoperative surgical images. Radiological configuration was classified as open, hooded, or covered depending on the extent of bony overhang. Surgical images were processed using Image J software to determine the amount of drilling required before the round window membrane is exposed. These images were classified according to the St. Thomas classification into 3 grades. RESULTS: In all patients, the axial cut showing the cochlear aqueduct was obtained. There were 12 cases in the open category, 17 in the hooded category, and 21 in the covered one. Intraoperatively, the actual findings were type I 12, type II 18, and type III 20. The correspondence between the expected and actual classification was correct in 8, 12, and 18 cases, respectively. Comparing the intraoperative findings with the expected radiological configuration, there was a good concordance with a statistically non-significant difference ( χ(2) = 0.2613; P = .87751). CONCLUSION: It is possible to predict the configuration of the round window niche on a single-axial computed tomography cut and plan the most suitable axis of approach and predict the amount of drilling expected to expose the round window membrane.