Phantom Stimulation for Cochlear Implant Users With Residual Low-Frequency Hearing.
Benjamin Krüger, Andreas Büchner, Waldo Nogueira
PMID 34593687WHAT IT FOUND
Electric plus phantom low-frequency stimulation did not clearly match electric plus acoustic low-frequency stimulation.
Both improved speech-in-noise scores compared with electric-only high-frequency stimulation, and adding phantom to electric plus acoustic stimulation worsened scores.
Key findings
01The baseline electric plus phantom low-frequency setting did not significantly differ from electric plus acoustic low-frequency stimulation in 9 analysable participants.
02Compared with electric-only high-frequency stimulation, electric plus acoustic low-frequency stimulation improved speech reception thresholds by a mean 4.31 dB in a group analysis of 11 participants, and electric plus phantom low-frequency stimulation improved thresholds in a group analysis of 9 participants for certain settings.
03Adding phantom stimulation to electric plus acoustic low-frequency stimulation worsened speech reception thresholds compared with electric plus acoustic alone for certain settings, with mean differences of 1.11 dB and 0.91 dB in 11 participants.
STILL TO COME
How it was doneWhat they foundWhat it means for SLPs
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What it does not show
The sample was small: 14 participants were enrolled, and group analyses included 11 participants for electric versus electric-acoustic comparisons and 9 participants for electric versus electric-phantom comparisons. Some participants could not complete all conditions: one was excluded after a 20 dB hearing loss worsening and inability to perform the sentence test, and two were included only for electric and electric-acoustic conditions. Two participants could not perform electric-only or phantom conditions without reaching the 25 dB signal-to-noise limit, so they were excluded from group analyses. Testing was acute. Participants practised only with electric-acoustic stimulation, then conditions were compared without giving time to adapt to electric-only or phantom settings. The study used one CI company and one electrode array, so results may not apply to other implant systems. Speech perception was measured in stationary noise, not competing talkers or fluctuating noise, where acoustic low-frequency hearing may matter more. The optimal phantom setting varied across participants, so there was no single setting that can be recommended. The study could not separate spectral overlap from spatial distance because cutoff frequency and electric-acoustic frequency difference were correlated. The authors described the study as single-blind, but the experimenter knew the condition being tested.
Declared interests
The authors declared no conflicts of interest.
The easy way to misread this
Do not conclude that phantom stimulation can routinely replace acoustic low-frequency amplification in cochlear implant users. The no-difference result between electric plus phantom and electric plus acoustic came from 9 participants who could perform the electric-only test, and two participants could not complete testing without acoustic stimulation. Also, when phantom stimulation was added to electric plus acoustic stimulation, speech-in-noise thresholds worsened.