Cochlear Implant Fitting Profiles in Children with Congenital Cytomegalovirus: One-Year Longitudinal Comparison with GJB2-Related Hearing Loss

Background/Objectives: Congenital cytomegalovirus (cCMV) infection is a major cause of paediatric sensorineural hearing loss and may involve peripheral and central auditory pathways. This study investigated longitudinal cochlear implant (CI) fitting parameters in children with cCMV-related hearing loss, including the influence of MRI-detectable brain abnormalities, using GJB2-related hearing loss as a reference. Methods: This retrospective multicentre study included 56 children (89 implanted ears) divided into cCMV, altered cCMV (with MRI abnormalities), and GJB2 groups. Outcomes were evaluated at activation and 1, 3, 6, and 12 months after activation using longitudinal mixed-effects models with participant and ear nested within participant as random intercepts. Results: Significant group-by-time interactions were identified for eCAP, impedance, C and T levels, and dynamic range. Adjusted eCAP differences were time-specific rather than uniform throughout follow-up. C and T levels showed no significant adjusted between-group contrasts, and dynamic range differed only between cCMV and GJB2 at 1 month. Aided PTA improved over time and was better in the cCMV group than in the other groups. CAP scores improved over time and were lower in the altered cCMV group than in both the GJB2 and cCMV groups. Conclusions: CI fitting parameters followed different longitudinal patterns across aetiological groups, but most between-group differences were time-specific. MRI abnormalities were associated with poorer functional auditory performance rather than a uniform electrophysiological profile. Objective fitting measures, aided audibility, and functional auditory performance should therefore be interpreted jointly during follow-up.