Cochlear Duct Length: Rethinking Its Role in Auditory Outcomes.

Objective: To assess the relation between cochlear duct length (CDL) and audiological outcome after cochlear implant surgery in prelingually deafened children. Methods: In a prospective cohort study, 36 prelingually deaf children underwent cochlear implantation at All India Institute of Medical Sciences, Jodhpur. Preoperative high-resolution computed tomography (HRCT) and high-resolution T2 weighted sequences magnetic resonance imaging (MRI) of temporal bones were used to calculate CDL. Patients were followed up for 12 months postoperatively with visits every three months for audiological scoring (infant-toddler meaningful auditory integration scale and revised central auditory processing scores). Results: Thirty-six candidates were included in the study. The mean CDL, as measured on temporal bone HRCT, was 32.72±1.278 mm, and, with MRI, was 33.4689±1.31. This study is suggestive of widely dispersed data (coefficient of variance <0.5), and hence, the hypothesis of "implantation in CDL close to 31.5 mm will give the best improvement in functional outcome scores" cannot be generalized. The improvement in functional outcome scores is likely attributable to other causes/multifactorial causation. Conclusion: We found no relationship between CDL and audiological outcomes post-cochlear implantation in prelingually deaf children. Further research with larger sample sizes, prospective multicenter designs and extended follow-up periods is warranted to strengthen evidence in this area.