Improving clinical practice for babies with hearing loss
Research type
Research Study
Full title
Improving clinical practice for babies with hearing loss
IRAS ID
172044
Contact name
Kevin Munro
Contact email
Sponsor organisation
Central Manchester University Hospitals NHS Foundation Trust
Duration of Study in the UK
1 years, 11 months, 26 days
Research summary
Research Summary
Childhood hearing loss is a potentially devastating long-term condition. For this reason, all babies get a hearing test soon after birth and hearing aids are now prescribed in infancy. However, there is an urgent need for test procedures that provide information about the necessity for, and appropriateness of, hearing aids in infants. We have completed an exploratory study on 100 normal-hearing babies using a promising solution called ‘Cortical Auditory Evoked Potentials’ (CAEPs). This test measures if sounds are being detected by the brain using recording leads attached to the head. The next step is to turn these findings into a routine clinical procedure for infants with hearing loss. For example, if a CAEP cannot be detected, does this mean that the hearing aid prescription needs to change in order for the infant is hear speech and develop good communication skills?
We will:
1. measure the proportion of infants in whom we can detect a CAEP for different sounds,
2. measure the proportion of infants who complete the CAEP procedure along with how long it takes to make the measurements, and
3. interview parents and invite them to complete a questionnaire in order for us to understand how acceptable they find the procedure.An innovative aspect of this project is the use of a mobile Hearing Research Van, a bespoke facility purchased especially for this project, because parents tell us that if we visit them, it will make it much easier for them to participate in the study.
Our team is skilled at: (i) undertaking research on infants, and (ii) introducing new developments into clinics.
By reducing the consequences of hearing loss, this project has the real potential to improve clinical practice at an earlier stage in the care pathway for infants with a potentially devastating long-term condition.
Summary of Results
• New computer-generated speech-like sounds were developed and tested in our labs. They are known as the ManU-IRU (Manchester University-Interacoustics Research Unit) stimuli. It was shown that these sounds are appropriate for testing hearing via hearing aids because they are processed and heard in the same way as speech. These new sounds are more continuous in level and cover a narrower frequency range compared to real-life speech. This helps us to know exactly what types of sounds can be heard via the hearing aids which is important for managing and counselling hearing loss.
• Using the ManU-IRU stimuli, we developed methods for testing how well babies with hearing loss can hear speech through their hearing aids using Cortical Auditory Evoked Potentials (CAEPs). This test is performed when babies are awake and alert, and requires no active response from the baby: it is all automatic. It is therefore a good test for young infants for whom reliable tests of hearing are not currently available.
• The CAEP test using the ManU-IRU stimuli:
o Is acceptable to caregivers and can be completed in an acceptable time (median 24 minutes, likely to be faster in a clinical scenario).
o Is a sensitive test for measuring which sounds can be heard, when repeat recordings are taking into account, particularly for our mid-frequency stimulus. For the mid frequency, when repeat testing was included, a response was seen 94% of the time for infants for whom the stimulus was over 10 dB above their threshold of hearing.
o Care should be taken when infants are vocalising during the test as this had a negative impact on how well the test performed.
o Automatic detection of CAEP responses also showed appropriately high specificity I.e. you are unlikely to accidentally detect a response which is not really there.
• As such the CAEP is a good candidate to supplement current clinical practice for babies with hearing loss. Data from the study has been incorporated into a national test protocol (Cortical Auditory Evoked Potential (CAEP) Testing, under final review Feb 2022).
• The ManU-IRU stimuli have been incorporated into one manufacturer’s clinical kit, and we are in discussions with other manufacturers about their incorporation into other devices.
• Automatic detection of CAEP responses in infants (to avoid relying on the expertise of the tester) was compared using a number of methods. The method in popular current use (Hotelling T2) was shown to be the most appropriate.
• Automatic detection of CAEP responses in adults (not the primary aim of this study) was compared using a number of methods. A method novel in terms of CAEP analysis (dynamic time-warping) was found to be superior to Hotelling T2. This new finding is yet to be incorporated into clinical testing kit.
• Daily hours of hearing aid use was found to decrease between 3-7 and 7-21 months of age, a finding not previously reported in the literature. The effect was dominated by infants with profound losses, many of who would go on to have cochlear implants, a hearing device implanted into the ear. NB regular hearing aid use in these infants is still important for their auditory development.
• A number of challenges faced by caregivers who look after infant hearing aid users were identified:
o Lack of confidence in troubleshooting and performing listening checks of the hearing aids
o Acoustic feedback (high-pitched whistling) from a poorly fitted hearing aid.
o Distractions of other children in the home
o Difficulty getting into a routine
o Aids not working correctly
o Long waits for audiology appointments
o Infants pulling aids out (worse for older infants)
• Caregivers also offered solutions and things that have/might have helped them:
o More information on what their infant can hear with/without aids
o Peer support
o Information for relatives/other carers
o More information on plan going forwards in audiology and what to expect in the future
o Early on: information on listening checks and cleaning aids
o Later on: information on keeping aids in ears and changing hearing aid tubing
• Listening skills were assessed using a questionnaire (e.g. “Does your child respond to a familiar voice?” YES/NO). Over time, more infants fell below the normative range than when the infants were very young. Scores from these infants were somewhat lower than some reports in the literature. Whilst there was an association between degree of hearing loss and listening skills, there was a lot of variation in scores for individuals within all categories of hearing loss.
• Another test for how well infants hear through hearing aids (the Auditory Steady-State Response, ASSR) was investigated using a novel modulated speech-like stimulus, which retains more natural speech qualities than the CAEP stimuli, but is also well-controlled in terms of how the results can be interpreted. This pilot data showed very promising results with a large number of infants showing a response to the novel sound stimuli, suggesting it would be a highly sensitive test.REC name
North West - Greater Manchester East Research Ethics Committee
REC reference
15/NW/0736
Date of REC Opinion
30 Sep 2015
REC opinion
Further Information Favourable Opinion