Tailored auditory implantation in inner ear malformations: A long-term prospective study integrating imaging and functional outcomes.

Abstract

Objective: This study aims to evaluate long-term auditory outcomes in patients with inner ear malformations (IEMs) treated with cochlear or auditory brainstem implants (CI/ABI), and to assess the influence of anatomical subtype, electrode design, insertion depth, and genetic/syndromic background on hearing performance over a 10-year follow-up.

Methods: We conducted a prospective cohort study including patients with radiologically confirmed IEMs and bilateral severe-to-profound hearing loss, all of whom underwent implantation and completed at least 10 years of follow-up. Outcomes were assessed using pure-tone average (PTA) and speech recognition scores (SRS) at defined intervals. Additional analyses explored the influence of electrode array design, insertion depth, genetic and syndromic diagnosis, and intraoperative complications.

Results: 82 patients were included in the study, of whom 71 (86.58%) received a CI, while the remaining 11 patients (13.41%) were treated with an ABI. After a 10-year follow-up, the mean PTA gain with CI was 64.56 ± 14.52 dB, and mean SRS improved by 56.88 ± 25.32%. On the other hand, patients treated with ABI presented a gain of 45.00± 18.22 and 32.62± 10.67% dB, respectively. Enlarged vestibular acueduct (EVA) had the highest 10-year SRS (80.04%), whereas cochlear nerve agenesis, Michel deformity, and cochlear hypoplasia type I had the lowest (23.72%, 24.00%, and 26.50%, respectively). Mean insertion depth was 19.66 ± 3.74 mm and showed a non-significant correlation with final SRS (r = 0.243, p = 0.084). The presence of residual auditory brainstem responses (ABR) responses was significantly associated with better pre-implant PTA (p = 0.041) and higher SRS at 10 years (p = 0.034). Finally, having a syndromic condition was not significantly associated with the risk of a worse SRS at 10 years post-implantation (p = 0.091), nor with poorer auditory outcomes measured in PTA prior to surgery (p = 0.315).

Conclusion: Auditory outcomes in IEMs are modulated by malformation subtype, neural status, and electrode design. A stratified, anatomy-guided approach is essential, especially when considering perimodiolar arrays. Delayed gains in some subtypes underscore the value of long-term follow-up, and integrating imaging and genetic data may enhance personalized implant strategies.