research round-up
40 • Positive experiences were reported from the post-study interviews with parents
of cases where a CAEP response is seen will be reported by different sensation levels in the study publication.
Current study – babies with hearing loss Following on from the normal hearing study, the team in Manchester developed a large-scale study performing aided CAEPs on babies with bilateral hearing loss who had been fitted with hearing aid(s). The study’s aim was to answer the following research questions:
Additional information is obtained by means of questionnaires and interviews to determine the acceptability of the procedure to parents. Similarly to the normal-hearing study, post-procedure questionnaires and interviews are completed to measure the acceptability of the procedure to parents.
1. Can aided CAEPs be reliably used in clinic to indicate physiological detection of speech in infants who wear hearing aids?
Recruitment, progress and next steps To date, the study has measured aided CAEP data from 103 babies and is currently following up with VRA data. The team are relying on Paediatric Audiology departments to continue identifying eligible families until March 2020. Every participant identified is invaluable in the quest to bridge the time gap between hearing aid fittings and behavioural assessment for babies with hearing loss. The research team recognise that it can be a challenging time to introduce a research study to families and are grateful for the support from audiologists and families.
2. Are the test procedures acceptable to families? Stimuli, study design and implementation Following consultation and discussion regarding recruitment, a bespoke mobile research unit was designed, purchased and commissioned to permit testing close to families’ homes. NHS Trusts from around UK agreed to act as participant identification centres. These centres have been providing our study information packs to families of infants newly diagnosed with permanent bilateral hearing loss. The research team created three synthetic speech-like stimuli (a low, mid and high frequency). The stimuli were designed to be significantly more frequency specific than other CAEP stimuli (such as used in the normal-hearing study); and to be treated like speech by hearing aids. In the current study, aided CAEPs are measured on infants aged 3-7 months using the mid and high frequency specially designed speech-like stimuli. The researchers return to see the family when the infant is around 9 months of age to perform aided Visual Reinforcement Audiometry, the gold standard behavioural assessment for this age group. Sensation level of the aided CAEP is predicted by using the VRA minimum response level. This allows the team to determine whether a CAEP response was present above aided threshold, i.e. showing a positive sensation level. The percentage
research round-up
In March 2019, the research team started using aided Auditory Steady State Response (ASSR) as an alternative electrophysiological method. Results for both the aided CAEP and aided ASSR will be reported in upcoming publications. If you work with infants with hearing loss and could help identify eligible families to take part in the study, please get in contact with the team via email: ladiesinthevan@manchester.ac.uk. Inclusion Criteria • Under 7 months (corrected age) at start of study • Fitted with hearing aids at the start of the study • Diagnosed with permanent bilateral hearing loss of any degree or type • No developmental delay that would likely significantly delay behavioural assessment (Visual Reinforcement Audiometry)
Take home messages The early normally-hearing study provided a positive foundation regarding the potential use of CAEPs to supplement current paediatric clinical practice for babies with normal hearing. Evidence suggests that aided CAEPs have the potential to: 1. Supplement current practice 2. Bridge the time gap between diagnostic Auditory Brainstem Response and Visual Reinforcement Audiometry 3. Provide early indications for Audiologists that alternative strategies may be required; such as the use of frequency lowering, or onward referral for cochlear implantation. Information of this sort at such an early stage has the potential to further benefit the lives of infants with hearing loss The next phase of this research will investigate whether aided ASSR measurements can be reliably used to indicate physiological detection of speech in infants who wear hearing aids and whether the test procedures are acceptable to families. Potential benefits of the ASSR over the CAEP include: (i) greater resilience to baby being asleep or awake during testing, (ii) faster test time due to multiple stimuli being tested simultaneously, and (iii) the sound stimuli being more speech-like in nature, being continuous rather than short duration (speech perception being the ultimate point of interest). One disadvantage is that the ASSR response can originate from widespread neural regions, across both the cortex and brainstem, so does not confirm cortical neural activity in the same way the CAEP does. We are optimistic that the current study will help inform future clinical practice and bridge the time gap between hearing aid fittings and behavioural assessment. Acknowledgements The normal-hearing study was funded by a strategic investment grant from Manchester University Hospitals NHS Foundation Trust, and was facilitated by the Manchester Biomedical Research Centre and Greater Manchester Local Research