What are the options for hearing aid management following aided cortical testing?

If the results of the aided cortical test suggest that changes or improvements can be made to the patient's device or amplification, then it is important to understand how and when to make such adjustments. This video will explore the options available for this, including understanding when not to make changes, how to make use of the full test battery of information to guide such changes and some practical suggestions for how to determine the most appropriate adjustments to make.

You can read the full transcript below.

When to change the hearing aid settings?

The results obtained from the aided cortical test can be used to guide hearing aid management for an individual patient.

It is important to remember that any changes and adjustments to hearing aid settings should be based on the fullest amount of information available, including feedback from parents, carers and other significant people involved with the patient, such as teachers and speech and language therapists.

It is also important to be mindful of when it is appropriate to make changes to the hearing aid settings and when not to.

In particular, when considering making changes or adjustments based on non-responses that indicate that a sound may not be heard by the patient, this should be made based on consistent and repeatable non-responses, not just one waveform.

This is to ensure that any non-response detected is a genuine non-response.

The data gathered by the Ladies in the Van study highlights that repeat testing increases the likelihood of detection [1].

Upon repeat testing, sensitivity values published in that study showed an increase from 80% to 94% for the mid-frequency stimulus, and from 60 % to 79 % for the high-frequency stimulus.

This study also looked at the impact of infant vocalizations, and found that the more vocal the child, the more likely it was that a non-response would be detected.

As already mentioned, changes to the hearing aid provision or settings must be made alongside other supportive information.

Supporting information from the test battery

Adopting a test battery approach allows for additional data and results to corroborate the findings of the aided cortical test.

Validated questionnaires such as LittlEars, PEACH and TEACH can be used.

Additional testing, such as tympanometry, can indicate whether there's any middle ear dysfunction that could explain unexpected results on the aided cortical test.

Performing HIT box measurements can help rule out any hearing aid faults that might also interfere with the results.

Ensuring an up-to-date RECD has been performed, ideally with new ear molds, is also important to ensure there's no leakage from the hearing aids, and that the correct amplification is being provided for use during the cortical test.

Lastly, parent or carer feedback should not be underestimated.

As the people spending the most amount of time with the patient, they can provide a valuable perspective on how well the hearing aids are working.

Likewise, any changes or adjustments to the patient's amplification should be made with informed parental or carer consent to ensure they are aware of the risks of and are able to detect any possible loudness discomfort.

Options for hearing aid adjustments

As it stands, there are currently no national guidelines for how to adjust hearing aid settings based on the aided cortical results using the Eclipse system and the available stimuli.

However, there are two broad options available if it is deemed that the current level of amplification is insufficient for the patient.

The hearing aid gain can be increased, however it is unclear by how much this should be adjusted in order to be certain of effective change.

As a result, the guesswork involved in increasing the gain can lead to loudness discomfort.

A far better option is to reprogram the audiogram to provide louder amplification.

In doing so, it is possible to make use of validated prescription formulae, which provide a higher degree of certainty by providing a target to be matched during the verification process.

The use of REMs or RECD measurements ensures we have control over the loudness level of the device through the MPO target and loud input level.

This approach of reprogramming the audiogram as opposed to increasing the gain is seen in the Australian guidelines for aided cortical testing.

Within this protocol it is recommended to revise the hearing thresholds by certain levels based on the cortical results.

However it should be noted that these recommendations adopt a one-size-fits-all approach whereby the full audiogram is adjusted based on the results obtained rather than addressing specific frequency regions of the audiogram.

This is likely due to the poor frequency specificity of the stimuli used.

Once hearing aid adjustments have been made it is required to perform further aided cortical testing to validate the newly prescribed amplification.

In cases where responses are not detected to the increased amplification based on the newly programmed audiogram, then clinicians are guided to refer to the speech-o-gram to assess whether audibility is to be expected.

If the speech-o-gram indicates that the stimuli presented via the aided cortical test are not likely to be audible, then the results align with the expectations for the patient's audibility and hearing aid provision.

If the speech-o-gram indicates that the stimuli are likely to be audible, then the results of the aided cortical test do not align with expectations, and this may be a case of false non-responses being detected.

In this instance, clinicians are guided to refer to the PEACH questionnaire to guide hearing aid management decisions instead.

The one-size-fits-all approach used by the Australian program does not work for the ManU-IRU stimuli due to their vastly greater frequency specificity.

The full audiogram range should not be changed based on the results obtained, but rather a more frequency-specific approach should be adopted.

If aided cortical responses are not detected, then it is recommended to refer to the REM traces and inspect the areas that relate specifically to the individual stimuli and levels tested.

If, for the non-response stimulus and level in question, the hearing aid output in that region is greater than 10 dB above threshold, then audibility can be considered to be expected.

In this scenario, the non-response on the aided cortical test does not align with expected audibility, and it is important to question why.

If all other elements of the test battery are accounted for, such as having up-to-date RECD measurements, good fitting ear moulds are being used, tympanometry is normal, etc., then the non-response to the aided cortical test could be attributed to insufficient amplification being provided due to the audiogram levels used.

In this case, increasing the audiogram by 10 dB and performing further aided cortical testing may be warranted.

If, instead, the hearing aid output of the REM trace is not greater than 10 dB above threshold, then the non-response of the aided cortical test aligns with the poor audibility expected from this hearing aid fitting.

The stimulus in question may not be audible due to the degree of hearing loss and the type of device provided, and the patient's onward management should be considered accordingly.

References

[1] Visram, A. S., Stone, M. A., Purdy, S. C., Bell, S. L., Brooks, J., Bruce, I. A., Chesnaye, M. A., Dillon, H., Harte, J. M., Hudson, C. L., Laugesen, S., Morgan, R. E., O'Driscoll, M., Roberts, S. A., Roughley, A. J., Simpson, D., & Munro, K. J. (2023). Aided Cortical Auditory Evoked Potentials in Infants With Frequency-Specific Synthetic Speech Stimuli: Sensitivity, Repeatability, and Feasibility. Ear and hearing, 44(5), 1157–1172.