Abstract
Neurodevelopmental changes occur with asymmetric hearing loss, limiting binaural/spatial hearing and putting children at risk for social and educational challenges. These deficits may be mitigated by providing bilateral hearing in children through auditory prostheses. Effects on speech perception and spatial hearing were measured in a large cohort of >450 children who were deaf and used bilateral cochlear implants or bimodal devices (one cochlear implant and a contralateral hearing aid). Results revealed an advantage of bilateral over unilateral device use but this advantage decreased as hearing in the two ears became increasingly asymmetric. Delayed implantation of an ear with severe to profound deafness allowed asymmetric hearing, creating aural preference for the better hearing ear. These findings indicate that bilateral input with the most appropriate device for each ear should be provided early and without delay during development.
Highlights
Cochlear implantation has become standard treatment for childhood deafness
Recent studies suggest that the aural preference syndrome can be reversed if symmetric/balanced bilateral input is provided during early developmental periods[27,28]
This study evaluated effectiveness, timing, and asymmetry of bilateral input in a large, diverse, and inclusive cohort of children who hear with bimodal devices or bilateral cochlear implants
Summary
Cochlear implantation has become standard treatment for childhood deafness. One cochlear implant promotes significant gains in speech understanding[1,2] and language development[3,4,5,6] when provided early in development. As revealed by electrophysiological and functional imaging studies, delaying access to sound in early childhood allows cortical cross-modal plasticity to reorganize auditory areas[20,21,22,23,24,25] as well as cortical areas involved in spatial attention and awareness[20,22,26] but treating only one of two ears with hearing loss leaves the second ear deprived of sound This creates a new problem termed the “aural preference syndrome”[7]. Studies with larger cohorts of children (≥50) suggest that children benefit from bilateral implants despite delays to bilateral input but longer delays impair performance in the second hearing ear, creating asymmetric abilities between the two ears for understanding speech[1,40,41,42,43] and for spatial hearing[44,45]. One of the main problems of relating existing speech perception data to electrophysiological findings is that only a few of the behavioural studies include children with very short or no delays to bilateral implantation[1,45], leaving a question about the most appropriate timing of bilateral input to prevent behavioural consequences of aural preference
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