Anatomy-Based Fitting for Cochlear Implants: Evaluation of Hearing Performance in Newly Implanted Cochlear Implant Users - A Randomized Clinical Trial

Objectives.: The current settings of cochlear implants (CIs) do not respect specific cochlear tonotopy, resulting in tonotopic mismatch and potentially decreased auditory performance. The development of new implant settings adapted to individual tonotopy, called anatomybased fitting (ABF), could improve the auditory information coding, particularly by making surrounding sounds more recognizable. This study aimed to evaluate whether ABF allows better environmental sound recognition in new CI users compared to the conventional setting (CS); and to investigate the effect of ABF on speech recognition in quiet and noise. Methods.: A prospective, randomized, double-blind, two-period cross-over study in 17 new CI users was performed between March 2022 and August 2024. Adult subjects were recruited from candidates selected for cochlear implantation within a single French university hospital. Newly implanted adult recipients of a MED-EL cochlear implant with an electrode array insertion angle greater than 540° were eligible. Subjects were randomized to receive either ABF or CS for 6 weeks, then switched to the other setting for the same duration. Audiometric testing, including Environmental Sound Identification Test (Test d'Identification des Sons de l'Environnement, TISE), speech audiometry in quiet using Fournier lists, and speech audiometry in noise (Vocale Rapide dans le Bruit, VRB) was performed at 6 and 12 weeks. Results.: Sixteen subjects (mean age 60 years [SD=15.1]) were analyzed. ABF showed a significant improvement in the TISE score (mean effect (ME)=1.2, 95% confidence interval (CI95%)=[0.3;2.0], standardized effect size (SES)=0.97, p=0.016). Speech recognition in quiet was statistically better with CS (ME=3.6, CI95%=[1.8;5.3], SES=1.4, p=0.001) while no statistically significant difference was found for speech recognition in noise (CI95%=[- 2.8;0.1], p=0.08). Conclusion.: In newly implanted cochlear implant users, ABF improved environmental sound recognition, suggesting improved perceived sound naturalness in the first weeks after implantation. This benefit did not extend to speech recognition in quiet and remains inconclusive in noise due to floor effect.