A/Prof. Gary Rance1
1The University of Melbourne, Carlton, Australia
Purpose: “Auditory neuropathy” (AN) is a term used to describe disorders in which afferent neural transmission through the auditory nerve and brainstem is disrupted, but cochlear (outer) hair cell function is normal. There are a number of pathologic mechanisms (involving both pre- and post-synaptic sites) capable of producing the AN result pattern. The aim of this study was to explore whether patient aetiology is a factor in long-term perceptual outcomes.
Materials and Methods: this presentation will provide a review the literature describing speech perception scores in affected individuals with known aetiologies. Data were segregated based on whether patient history, genetic profile and/or imaging studies suggested a pre- or post-synaptic mechanism.
Results: The effect of acoustic interventions (hearing aids) were broadly similar for both pre- and post-synaptic forms of AN. In cochlear-implant recipients, however, site-of-lesion appeared to greatly affect post-operative performance. CI-outcomes for those individuals thought to have a pathologic locus distal to the spiral ganglion neurons (SGN) were consistently positive. Results for those with neuropathy affecting the SGN or more proximal auditory pathway sites were diverse, with around 50% showing negligible perceptual ability. Mean open set speech perception score for the pre-SGN group was 72.3±19.9% and for the SGN and beyond group was 28.7±35.0% (P<0.001).
Conclusion: Cochlear implant outcome in individuals with AN can be unpredictable when the neuropathy affects the SGN, auditory nerve and brainstem pathways. In such cases, the CI-generated signal must still pass through a damaged neural system
Gary Rance is an audiologist, clinical researcher and Professor at the University of Melbourne. He is Director of Academic Programs for the Department of Audiology and Speech Pathology and coordinates the clinical research units for the Master of Clinical Audiology and Master of Speech Pathology programs. His research areas have included auditory evoked potentials, cochlear implants in children, and the perceptual effects of both permanent and transient hearing loss. He has also been a leader in the field of auditory neuropathy (AN) and was responsible for the first publications to describe this form of hearing deficit in newborn babies.