Longitudinal Correlation of Frequency-to-Place Mismatch and Postoperative Speech Perception Outcomes in Cochlear Implant Recipients: Monosyllable, Consonant, Word, and Sentence

Background/Objectives: Frequency-to-place mismatch between cochlear implant (CI) electrodes and cochlear tonotopy has been suggested to affect postoperative speech perception. This study aimed to examine the associations between frequency-to-place mismatch and speech perception outcomes across multiple linguistic levels in patients with CI and to assess how these associations change over time using postoperative computed tomography. Methods: This retrospective cohort study included 44 postlingually deafened adults who underwent unilateral cochlear implantation with a Flex28 electrode by a single surgeon at a tertiary care hospital. Speech perception was assessed using CI-2004, a Japanese speech perception test consisting of monosyllables, consonants, words, and sentences, in quiet settings at 3, 6, and 12 months after CI activation. Partial correlation analyses between frequency-to-place mismatch and postoperative speech perception scores were performed in 35 of the 44 patients, controlling for age and mean preoperative pure-tone thresholds. Results: Negative associations were observed between frequency-to-place mismatch and CI-2004 scores, particularly for monosyllable and consonant perception in uncorrected analyses. After correction for multiple comparisons, only consonant perception at 3 months after CI activation remained significant (r = −0.52, p = 0.002). Similar patterns were observed for other speech measures and at later time points, although these did not remain significant after correction. Conclusions: Frequency-to-place mismatch was associated with postoperative speech perception outcomes, particularly those involving phoneme-level recognition. After correction for multiple comparisons, only consonant perception at 3 months after CI activation remained significant.