Comprehensive evaluation of cochlear implantation in otosclerosis: radiological, technical, and audiological outcomes...

To comprehensively assess insertion characteristics, auditory performance, and cochlear implant fitting outcomes in a large cohort of implanted patients with otosclerosis, in comparison with a control group of implanted non-otosclerotic individuals. The most of the otosclerotic patients had retrofenestral otosclerosis and were indicated to cochlear implantation because of deafness.

Retrospective observational cohort study.

Tertiary referral center.

A group of 49 patients (54 implanted ears) with otosclerosis who received a Cochlear Nucleus 512 or Freedom 24RE between 2009 and 2015 were included, along with a control group of 577 patients (599 implanted ears) with hearing loss due to causes other than otosclerosis, osteogenesis imperfecta, meningitis, head trauma, temporal bone fracture, labyrinthitis, or prior middle ear surgery. All patients were implanted with the same type of electrode.

Audiometric data were collected from routine fitting and re-fitting appointments using the Freiburg Monosyllabic Test and the Hochmaier-Schulz-Moser test in 10 dB noise (HSM 10 dB). Electrode impedance values, Neural Response Telemetry (NRT), C-levels, the incidence of facial nerve stimulation, and electrode deactivation during the fitting process were also assessed in both groups. For the otosclerotic patients, postoperative radiologic data included measurements of the electrode insertion angle.

Patients in the otosclerosis group achieved a median score of 50% in the Freiburg Monosyllabic Test by the end of the first fitting week, followed by further improvement within the first year and a plateau at approximately 65%. Five years post-implantation, they achieved a mean score of 40% on the HSM 10 dB test. No statistically significant differences were observed in the audiometric test results between the otosclerosis and control groups. Impedance values in the otosclerosis group were significantly higher than in the control group. In both groups, impedances decreased after the first fitting up to the 3 months appointment, and then remained stable over the following 5 years. No statistically significant differences were observed in NRT or C-levels between the two groups. However, facial nerve stimulation occurred significantly more often in the otosclerosis group, with an incidence of 29%. The median insertion angle in the otosclerosis group was 368°, and a statistically significant positive correlation was found between insertion angle and Freiburg test scores, as determined by Pearson correlation analysis.

Despite challenging anatomical conditions and increased postoperative impedances, there are no differences in audiological performance between patients undergoing cochlear implantation with compared to without otosclerosis. Patients with otosclerosis are significantly more likely to experience facial nerve stimulation. However, regarding the deactivation of electrodes overall and postoperative fitting parameters, no further differences emerge compared to the control group.