Comparative analysis of cochlear duct length using computed tomography in South Indian and Scottish populations: Implications for cochlear implant electrode selection

PURPOSE: Cochlear duct length (CDL) varies among individuals and populations, influencing cochlear implant (CI) electrode choice, insertion depth, and postoperative outcomes. Most CI electrode arrays are designed using Caucasian anatomical data, with limited evidence from South Asian populations. This study aimed to compare CDL between South Indian and Scottish cohorts and explore implications for population-specific CI electrode selection. METHODS: A retrospective cohort study analysed temporal bone CT scans comprising 100 cochleae from the South india cohort and 100 cochleae from the Scottish cohort. CDL was estimated using the Alexiades formula, derived from A-values measured on coronal CT images along the mid-modiolar axis. All measurements were validated independently by senior consultants to ensure accuracy and reproducibility. RESULTS: Mean CDL was significantly shorter in the South Indian group (26.38 ± 2.00 mm) compared with the Scottish group (33.07 ± 1.19 mm), showing an absolute difference of 6.70 mm (p < 0.001). The corresponding A-values were also smaller in the South Indian cohort (7.30 ± 0.48 mm vs. 8.91 ± 0.28 mm; p < 0.001). CONCLUSION: Significant differences in estimated CDL were identified between the South Indian and Scottish cohorts. These morphometric findings demonstrate anatomical variation between the studied populations. However, their implications for cochlear implant electrode selection and clinical outcomes require prospective validation.