Cone-Beam CT of the Temporal Bone: Normative Linear Biometry of Inner Ear Structures

Background and purpose: Normative linear measurements of inner ear structures may enhance diagnostic accuracy in detecting subtle congenital abnormalities. This study aimed to establish Cone-Beam Computed Tomography (CBCT)-based normative reference values for temporal bone anatomy. Materials and methods: We retrospectively reviewed consecutive CBCT scans of normal temporal bones acquired between June 2022 and June 2024. Scans were classified as normal based on the absence of pathological findings and no history of otologic disorders. Eleven linear measurements of inner ear structures were independently performed by two radiologists, and interobserver agreement was assessed. Reference centiles were generated for each parameter. Results: A total of 319 patients (135 men, 184 women; mean age, 50.03 years; range, 3 months-91 years) were included. Interobserver reliability was high across all measurements. Age and sex showed a small effect on any measurement. Normative centile distributions for all eleven structures were established. Conclusions: This study provides robust CBCT-derived normative linear measurements of inner ear structures. These reference values may improve radiologic assessment of congenital hearing loss, particularly in patients with normal-appearing CT examinations.