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Post-operative stapedius reflex tests with simultaneous loudness scaling in patients supplied with cochlear implants
1Department for Hearing, Speech and Voice Disorders, University of Innsbruck, Austria.
Summary
Electrical stapedius reflex threshold (ESRT) measurements accurately estimate maximum comfort loudness levels (MCL) in cochlear implant users. This method aids in effective speech processor fitting and prevents overstimulation.
Area of Science:
- Audiology
- Biomedical Engineering
- Neuroscience
Background:
- Cochlear implants (CIs) aim to restore hearing but require precise fitting for optimal user benefit.
- Determining comfortable loudness levels is crucial for effective CI programming.
- The stapedius reflex, a middle ear muscle contraction, can be elicited electrically in CI users.
Purpose of the Study:
- To investigate the efficacy of measuring electrically elicited stapedius reflex thresholds (ESRT) for estimating maximum comfort loudness levels (MCL) in cochlear implant users.
- To evaluate the feasibility of simultaneous loudness scaling during stapedius reflex testing.
Main Methods:
- Measurements were conducted on six experienced cochlear implant users with the COMBI 40 system.
- An up/down stimulation protocol near the reflex threshold was used for simultaneous testing of stapedius reflex and loudness scaling.
- Automated recording of both procedures was employed.
Main Results:
- A high overall correlation (r=0.92) was found between ESRT and MCL.
- ESRT and MCL showed similar dependencies on the stimulated channel.
- Loudness scaling at the reflex threshold varied from normal to loud.
- The stimulus intensity range for ESRT was narrower than for specific loudness categories.
Conclusions:
- ESRT measurements can be successfully applied for speech processor fitting in cochlear implant users when the stapedius reflex is detectable post-operatively.
- Simultaneous loudness scaling effectively helps avoid overstimulation during the implant's use.