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.
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ItemCommunication outcomes for children who receive a cochlear implant before 2 1/2 years of age( 2015)Background and aims: This study examined the long-term benefits of cochlear implantation for children who received their first cochlear implant before 2.5 years of age. Using a comprehensive battery of speech perception, speech production and language measures over six years, the study compared communication outcomes for children using cochlear implants and children with normal hearing. The relative influence of age at cochlear implantation and other covariates on outcome measures was examined. Method: The study design involved the prospective longitudinal evaluation of 32 children with no additional disabilities, who received their first cochlear implant before 2.5 years. Speech perception skills were quantified using the CAP pre-operatively and at one, two and three years’ post-implantation. When the children entered primary/elementary school (five years of age), open-set word testing (CNC) was completed. Speech production was evaluated using the DEAP at school entry. Language was evaluated pre-implantation, at one, two and three years post-implantation, and at school entry using the RI-TLS, PPVT and the CELF or PLS when relevant. Results: All children in the study developed significant open-set speech perception skills with a group mean monosyllabic word score of 56% and phoneme score of 81%. Speech production skills were delayed compared to normally hearing peers at school entry. Rate of language development for the children (M 1.04) and standard scores (M 86) at school entry were equivalent to hearing peers. Younger age at implantation was found to significantly reduce language delay and was associated with optimum speech production at school entry. There was no significant relationship between age at implantation and language growth, language standard score at school entry or speech perception. Measures of family participation and child non-verbal IQ were significantly associated with speech perception, speech production and language. Conclusion: Children with cognitive development within the typical range who receive a cochlear implant before 2.5 years of age, can demonstrate speech perception skills sufficient to communicate using audition alone. This level of speech understanding however, does not lead to age appropriate speech production in all cases. In the present study, speech production was delayed compared to hearing peers. Children who receive their first cochlear implant before 2.5 years can demonstrate rates of language acquisition equal to their hearing peers, but may retain a language delay approximately equal to their age at implantation. This data supports the provision of cochlear implants as early as possible to minimise any language delay resulting from an initial period of auditory deprivation.