Cochlear size variation in a large-scale international multicentre cohort.
AIM: This study aims to (1) review the literature on cochlear size, measured by the A-value, to assess reported variation across studies, and (2) consolidate cochlear parameters-specifically basal turn diameter (A-value) and width (B-value)-measured using the standardized DICOM viewer OTOPLAN®, and compare these with published data. METHODS: A scoping literature review was conducted using the search term "diameter of cochlear basal turn" to identify studies reporting A-value measurements. To complement this, cochlear measurements obtained with OTOPLAN® were collected from clinical collaborators across multiple international centres. The ratio of B- to A-values, which defines the cochlear basal turn shape, was calculated as previously described by Khurayzi et al. (2021). RESULTS: The literature review identified 38 studies comprising 5,206 A-value measurements (average: 9.08 mm; range: 8.01-10.03 mm). Additionally, 5,580 OTOPLAN® measurements were collected from 43 clinics across 25 countries (mean: 9.07 mm; range: 6.67-11.45 mm). Overall, 68.7% of cochleae exhibited an elliptical basal turn shape. CONCLUSION: Using a large, international multicentre dataset and a standardized measurement tool, this study demonstrates substantial variation in cochlear size and shape across clinical cohorts from different regions. The mean A-value (9.07 mm) is consistent with previously published literature, while the wider observed range highlights greater anatomical variability within a multicentre clinical population than previously reported. The majority of cochleae demonstrate an elliptical basal turn configuration.