Interaction Between Electric and Acoustic Stimulation Influences Speech Perception in Ipsilateral EAS Users.
Marina Imsiecke, Benjamin Krüger, Andreas Büchner and 2 others
PMID 31592902WHAT IT FOUND
In 15 combined implant and hearing-aid users, overlap fitting worsened speech in noise compared with standard split and masking-adjusted maps.
The masking-adjusted map did not beat standard split fitting.
Key findings
01In the EAS listening mode, the overlap map had a mean SRT of -1.0 dB, worse than the meet map at -1.9 dB and the UNMASKfit map at -2.0 dB; meet and UNMASKfit were not significantly different.
02Ten subjects had significant electric masking, and it was strongest when electric and acoustic stimulation sites were one to two octaves apart.
03In stationary noise, the overlap map's speech scores became worse as electric masking became stronger.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
Only 15 of 18 participants completed the full study, and two additional subjects dropped out after trying the overlap fitting. The sample was small and highly variable in residual hearing, electrode insertion, and masking strength, so group averages may not apply to an individual patient. Four subjects could not complete the acoustic-only speech test, so acoustic-only performance was not available for everyone. The masking-adjusted map was not tested against a larger control group; some subjects received a mean UNMASKfit map rather than an individualized one. Four weeks may not be enough time to adapt to a new electric frequency map, and users often preferred their familiar meet fitting. The psychoacoustic masking measurements are longer than typical clinical appointments, so the masking-adjusted fitting may not be practical without simpler tests. The study did not identify why masking occurs, and the frequency-place map used to describe electric-acoustic distance may be imperfect for variable insertion depths. The study only tested ipsilateral electric-acoustic stimulation, so it does not show what happens for other hearing aid or cochlear implant configurations.
The easy way to misread this
Do not conclude that the masking-adjusted UNMASKfit map is better than the standard meet map. It was not significantly different from meet, and the main actionable result was that overlap fitting worsened speech in users with strong masking.