Association of Superior Semicircular Canal Roof Thickness With Age and Sex on Photon-counting Detector CT in a Japanese Cohort

OBJECTIVE: To quantify superior semicircular canal (SSC) roof thickness using ultra-high-resolution photon-counting detector CT (PCD-CT) and to evaluate its cross-sectional association with age and sex. STUDY DESIGN: Retrospective cross-sectional study. SETTING: Tertiary referral center. PATIENTS: 576 ears from 288 consecutive patients (mean age 42.7±27.3 y; range 0-89; 154 males, 134 females) undergoing clinically indicated temporal bone PCD-CT. MAIN OUTCOME MEASURE: Minimal SSC roof thickness on Pöschl-plane reconstructions (0.2 mm slice thickness), with intrarater and inter-rater reliability assessed. RESULTS: Reliability was excellent (intrarater ICC 0.966; inter-rater ICC 0.939). A linear mixed-effects model in the full cohort revealed a significant age × sex interaction (B=0.004, P=0.016): females showed no cross-sectional age-related change (B=0.000 mm/year), while males showed a small positive association (B=0.004 mm/year; ∼0.04 mm/decade). In a prespecified pediatric subgroup (<20 years; 84 patients), males showed significant cross-sectional thickening (+0.031 mm/year, P=0.001) and a similar trend in females (+0.020 mm/year), and females had thicker SSC roofs than males (0.88 vs. 0.70 mm at 7.7 years; P=0.039). The interaction was nonsignificant within both the pediatric (P=0.431) and adult (P=0.204) subgroups separately, indicating that the full-cohort interaction likely reflects the developmental phase difference between childhood and adulthood. CONCLUSIONS: SSC roof thickness does not decrease with age during adulthood, while active cross-sectional thickening occurs during childhood, suggesting that bony coverage is largely established during the first two decades of life. Adult-onset SSCDS likely reflects the interaction between congenitally thin coverage and secondary factors-intracranial pressure dynamics, mechanical events, and biomechanical changes-rather than progressive resorption.