Longitudinal outcomes of auditory and spoken language skills following unilateral and bilateral cochlear implantation in children and young adults with inner ear malformations

ABSTRACT Introduction Severe-to-profound sensorineural hearing loss significantly impairs spoken language acquisition and cognitive development. Cochlear implants (CIs) bypass damaged inner ear structures to directly stimulate the cochlear nerve and represent an effective rehabilitation strategy. Inner ear malformations (IEMs) are frequently associated with congenital hearing loss; however, the influence of anatomical variability on postoperative functional outcomes remains incompletely understood. Objective: To investigate the longitudinal trajectories of auditory skills, spoken language development, and speech perception following cochlear implantation in patients with radiologically confirmed IEMs. Methods A retrospective longitudinal observational study was conducted at a national tertiary referral center including 19 patients (22 implanted ears) with IEMs. Demographic, anatomical, surgical, and audiological variables were analyzed. Longitudinal changes in Auditory and Language Categories were evaluated using Linear Mixed Models (LMMs), whereas cross-sectional comparisons were performed using Fisher's Exact, Mann–Whitney U, and Kruskal–Wallis tests. Results Significant longitudinal improvements were observed in both Auditory and Language Categories throughout the 24-month follow-up (Time effect, p < 0.001). For Auditory Category, the LMM demonstrated a significant Time × EVA interaction ( p = 0.017), indicating a steeper rate of auditory improvement in patients with enlarged vestibular aqueduct (EVA) than in those with other malformations. In contrast, Language Category improved similarly in both groups, with no significant Time × EVA interaction ( p = 0.998). Open-set word and phoneme recognition also improved significantly after 12 and 24 months ( p < 0.001). Exploratory analyses demonstrated that greater anatomical severity was associated with poorer auditory outcomes at 12 and 24 months. Conclusion Cochlear implantation resulted in progressive improvements in auditory skills, spoken language, and speech perception during the first two postoperative years. Although auditory performance improved across all malformation types, patients with EVA exhibited a faster longitudinal auditory recovery, while spoken language development followed comparable trajectories irrespective of anatomical subtype.