Imaging Analysis for Cholesteatoma Extension to the Perilymphatic Space in Labyrinth Fistulae.

Objectives/Hypothesis: Disturbed perilymph behind a labyrinth fistula can lead to hearing deterioration; thus, delicate manipulation is required during surgery for cholesteatomatous fistulae with matrix extension to the perilymphatic space (EPS). However, it remains challenging to identify the EPS preoperatively. This study aimed to evaluate the diagnostic value of computed tomography (CT) for preoperative prediction of the EPS of cholesteatomatous fistulae. Study Design: Retrospective study. Methods: We included serial high‐resolution CT images showing a cholesteatomatous bone defect in the lateral semicircular canal (LSC) requiring mastoidectomy. CT and intraoperative findings were analyzed retrospectively. Using axial CT planes, we evaluated the length and angle between the margins of bone defects. Receiver operating characteristic (ROC) curves were constructed to determine the cutoff points. Results: We extracted data from 30 bone defects, of which six (20.0%) showed EPS intraoperatively. Bone defects with EPS (n = 6) had significantly greater length and angle values than those without EPS (n = 24) (P <.001 for both, Wilcoxon rank sum test). For length and angle, the area under the curve was 0.944 (95% confidence interval [CI]: 0.858‐1.000) and 0.951 (95% CI: 0.875‐1.000), respectively, according to the ROC analysis, and the optimal cutoff values were 3.65 mm and 71.6°, respectively, with 100% sensitivity and 91.67% specificity for both. Conclusions: Results demonstrated that a length >3.65 mm and an angle >71.6° for LSC bone defects on axial CT images are reliable diagnostic markers of EPS. Preoperative high‐resolution CT analysis can provide surgeons with a more conscientious preparation for handling deeper labyrinth fistulae. Level of Evidence: 4 Laryngoscope, 131:E1301–E1307, 2021 [ABSTRACT FROM AUTHOR]