Speech Perception Outcomes with the Anatomy-Based Fitting Map Among Experienced, Adult Cochlear Implant Users: A Longitudinal Study.

Introduction: Anatomy-based fitting (ABF), a relatively new technique for cochlear implant programming, attempts to lessen the impact of the electrode insertion location-related frequency-to-place mismatch (FPM). This study aimed to compare vowels and consonant perception in quiet and in noise among experienced adult cochlear implant (CI) users using the ABF and the regular, conventional-based fitting (CBF) map (pre-ABF) over six months.

Method: Nine ears from eight experienced adult CI users were included in the experimental and longitudinal research. Using surgical planning software called Otoplan, post-operative computed CT scans were used to determine the locations of intracochlear electrodes and their angle of insertion. The anatomy-based frequency bands were produced by Maestro 9.0 CI fitting software using the Otoplan data. Nonsense syllables with consonant-vowel-consonant (CVC) recognition scores in quiet and noise (+5dB SNR) were compared at baseline, three, and six months after ABF. The vowels involved were /a, i, u/, while the consonants were voiced /b, d, g/ and voiceless /p, t, k/ plosives. Speech pieces were presented at 30 dB SL in a sound-treated room through a loudspeaker positioned at 0° azimuth.

Results: On average, the ABF maps shifted center frequency ranging from 0.46 semitones (0.04 octave) at (E12) to 23.94 semitones (1.99 octave) at (E1) as compared to the CBF maps. The mean vowel and consonant identification scores in quiet and in noise were significantly higher in ABF than in CBF (p<0.05) with a large effect size and the trend of improvement was seen with time. Voiced consonants had better scores than the voiceless consonants.

Conclusion: The results demonstrated improved perception of vowels and consonants, particularly for sounds containing voicing cues after using the ABF maps. The results also suggested that ABF could be more effective for voice detection in noise. Overall, the findings indicate that correcting place mismatch with an ABF map may improve speech perception, at least among experienced adult cochlear implant users.