Audiology and Speech Pathology - Theses
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ItemAn evidence-based pathway to early cochlear implantation in infants: reducing the reliance on the behavioural audiogram( 2023-03)ABSTRACT Background and Aims Cochlear implantation has emerged as a leading hearing intervention for infants born with severe to profound hearing loss. Research has shown that early intervention with a cochlear implant (CI) can significantly improve speech perception and oral language development in infants, providing them with access to the sounds that are critical for language acquisition. However, studies investigating the relationship between initial electrophysiological hearing thresholds and subsequent behavioural thresholds have demonstrated uncertainty as to whether initial results are able to provide an accurate estimation of an infant’s functional hearing. This estimation must be accurate if a CI is to be considered before behavioural audiometry has been obtained, as CI surgery is likely to remove any remaining natural hearing. This study aims to explore the variance between initial electrophysiological thresholds and subsequent behavioural hearing thresholds in young infants with suspected severe to profound hearing loss in a clinical setting, to determine under which conditions initial electrophysiological results can be used to support a CI recommendation in the absence of behavioural audiology. It also aims to propose evidence-based recommendations for implementation of a paediatric CI candidacy pathway for cases in which reliance on behavioural audiometry can be reduced. Method A prospective cohort study of 63 infants with suspected severe to profound hearing loss, referred to the Cochlear Implant Clinic, Melbourne, before 12 months of age. Assessment protocol included auditory brainstem response, auditory steady-state response, otoacoustic emissions, tympanometry, cortical auditory evoked response, and behavioural audiometry. Data was explored using correlational analysis, linear regression, and clinical decision analysis. Results 90.8% of all individuals who met CI candidacy criteria with initial electrophysiological testing (3FAHL>85dB) also met criteria upon behavioural testing. This proportion increased to 95% once certain exclusion criteria were placed on the group, excluding children born prematurely and children with auditory neuropathy. This result indicates that, under certain conditions, initial electrophysiological thresholds may be reliable enough to form the basis of a CI recommendation. Sensitivity and specificity of diagnostic electrophysiological testing was also found to increase once exclusion criteria were applied. Conclusion For most infants undergoing CI candidacy evaluation, initial electrophysiological thresholds were an accurate reflection of their subsequent behavioural hearing thresholds. An alternative CI candidacy pathway is recommended for infants who show profound sensorineural hearing loss on initial electrophysiological testing in the absence of middle ear effusion or auditory neuropathy features, to provide CI recommendations before behavioural thresholds are obtained. This would lead to reduced timeframes between hearing loss identification, diagnosis, and implantation, which can improve oral speech and language outcomes.