Aided Cortical Auditory Evoked Potentials in Infants with Frequency Specific Synthetic Speech Stimuli: Sensitivity, Repeatability, and Feasibility

Objectives: The Cortical Auditory Evoked Potential (CAEP) test is a candidate for supplementing clinical practice for infant hearing aid users and others who are not developmentally ready for behavioural testing. Sensitivity of the test for given sensation levels (SLs) has been reported to some degree, but further data are needed from large numbers of infants within the target age range, including repeat data where CAEPs were not detected initially. This study aims to assess sensitivity, repeatability, acceptability, and feasibility of CAEPs as a clinical measure of aided audibility in infants.
Design: One hundred and three infant hearing aid users were recruited from 53 paediatric audiology centres across the UK. Infants underwent aided CAEP testing at age 3-7 months to a mid-frequency (MF) and (mid-)high-frequency (HF) synthetic speech stimulus. CAEP testing was repeated within seven days. When developmentally ready (aged 7-21 months), the infants underwent aided behavioural hearing testing using the same stimuli, to estimate the decibel sensation level (dB SL, i.e. level above threshold) of those stimuli when presented at the CAEP test sessions. Percentage of CAEP detections for different dB SLs are reported using an objective detection method (Hotellings T2). Acceptability was assessed using caregiver interviews and a questionnaire, and feasibility by recording test duration and completion rate.
Results: The overall sensitivity for a single CAEP test when the stimuli were ≥ 0 dB SL (i.e. audible) was 70% for the MF stimulus and 54% for the HF stimulus. After repeat testing, this increased to 84% and 72%, respectively. For SL >10 dB, the respective MF and HF test sensitivities were 80% and 60% for a single test, increasing to 94% and 79% for the two tests combined. Clinical feasibility was demonstrated by an excellent >99% completion rate, and acceptable median test duration of 24 minutes, including preparation time. Caregivers reported overall positive experiences of the test.
Conclusions: By addressing the clinical need to provide data in the target age group at different SLs, we have demonstrated that aided CAEP testing can supplement existing clinical practice when infants with hearing loss are not developmentally ready for traditional behavioural assessment. Repeat testing is valuable to increase test sensitivity and for clinical application, it is important to be aware of CAEP response variability in this age group.