THE EFFECTS OF ELECTRODE-MODIOLAR INTERFACE CHARACTERISTICS ON ELECTROPHYSIOLOGICAL AND FUNCTIONAL OUTCOMES IN ADULT PATIENTS UNDERGOING COCHLEAR IMPLANTATION.

Sensorineural hearing loss represents a major indication for cochlear implantation (CI), which restores auditory function by electrically stimulating the auditory nerve. However, outcomes depend on multiple factors, including the anatomical relationship between the electrode array and the modiolus, defined as the electrode-modiolar interface. In this context, electrode-modiolar distance (EMD) and angular insertion depth (AID) are key parameters influencing neural stimulation efficiency and hearing performance. This study aimed to assess the impact of EMI characteristics on electrophysiological and functional outcomes in adult CI recipients, comparing perimodiolar (PM) and lateral wall (LW) electrodes, and analyzing differences among the leading manufacturers. Additionally, the study evaluated longitudinal changes in clinical parameters up to 12 months post-activation, and the role of different fitting strategie (behavioral versus anatomy-based fitting).The results showed significant differences between PM and LW arrays in terms of impedance, ECAPs, and M/C levels, with slightly better hearing outcomes in patients with LW electrodes, likely due to their greater insertion depth rather than a reduced EMD. Among the different manufacturers, all devices demonstrated favorable outcomes, though devices with longer and more flexible arrays, often used in conjunction with anatomy-based fitting, tended to yield particularly consistent results in some patient groups. Anatomy-based fitting proved especially beneficial in post-lingual patients, promoting more selective neural recruitment and reduced current spread, with a positive impact on speech perception. In pre-lingual patients, this benefit appeared less pronounced, suggesting a stronger dependence on neural plasticity and long-term rehabilitation.These findings support the importance of a personalized approach to cochlear implantation, tailored to the individual cochlear anatomy and supported by advanced imaging and fitting technologies. Future studies should include longer follow-up, a broader patient population (including pediatric recipients), and integration of emerging technologies such as artificial intelligence, to further refine electrode selection and programming strategies—ultimately aiming to optimize clinical outcomes and quality of life in patients with severe-to-profound hearing loss.