Abstract Introduction: Cochlear implant (CI) extracts the frequencies from the sounds, but the frequency distribution to the electrode contacts often does not match with their location inside the cochlea (electro-acoustic mismatch). In patients with bilateral CIs, the pitch-place mismatch adds to the misalignment of the electrodes between the two sides (electro-electrical mismatch). Our objectives were to measure the electro-electrical mismatch between the two CIs, propose a method to correct it (psycho-acoustic based fitting PBF), and evaluate its effects on pitch discrimination, speech perception in noise, and music abilities. Materials and Methods: We measured the mismatch of each electrode contacts between the two sides, and a new personalized frequency map was created for the CI with the worst outcome based on the results of the electro-electrical pitch-matching test. The Oldenburg test, used to evaluate speech perception, the Pitch discrimination test (PDT), the songs identification test, and the Melodies identification test (MIT) used to measure music abilities were performed before and after the correction. Results: We enrolled 24 patients with bilateral CI (43.6 ± 17.3 years). All patients had electro-electrical mismatch (mean 8.5 ± 5.6 electrode contacts). We found a significant decrease of SRT 1 month after PBF (from −0.34 ± 1.9 to −2.74 ± 1.7; P < 0.001) and it remained stable after 3 months (−2.84 ± 1.8). PDT ( P = 0.020) and MIT ( P = 0.038) statistically improved after 1 month. PBF also caused a significant improvement in frequency discrimination ( P = 0.047). Conclusion: The correction of the electro-electrical mismatch between the two sides in patients with bilateral CIs could ameliorate the central merging of the auditory signals through the alignment of spectral perception.
Nardo et al. (Tue,) studied this question.