Tinnitus with a normal audiogram:relation to noise exposure but no evidence for cochlear synaptopathy

Guest, Hannah and Munro, Kevin J. and Prendergast, Garreth and Howe, Simon and Plack, Christopher J. (2016) Tinnitus with a normal audiogram:relation to noise exposure but no evidence for cochlear synaptopathy. Hearing Research. ISSN 0378-5955

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Abstract

In rodents, exposure to high-level noise can destroy synapses between inner hair cells and auditory nerve fibers, without causing hair cell loss or permanent threshold elevation. Such “cochlear synaptopathy” is associated with amplitude reductions in wave I of the auditory brainstem response (ABR) at moderate-to-high sound levels. Similar ABR results have been reported in humans with tinnitus and normal audiometric thresholds, leading to the suggestion that tinnitus in these cases might be a consequence of synaptopathy. However, the ABR is an indirect measure of synaptopathy and it is unclear whether the results in humans reflect the same mechanisms demonstrated in rodents. Measures of noise exposure were not obtained in the human studies, and high frequency audiometric loss may have impacted ABR amplitudes. To clarify the role of cochlear synaptopathy in tinnitus with a normal audiogram, we recorded ABRs, envelope following responses (EFRs), and noise exposure histories in young adults with tinnitus and matched controls. Tinnitus was associated with significantly greater lifetime noise exposure, despite close matching for age, sex, and audiometric thresholds up to 14 kHz. However, tinnitus was not associated with reduced ABR wave I amplitude, nor with significant effects on EFR measures of synaptopathy. These electrophysiological measures were also uncorrelated with lifetime noise exposure, providing no evidence of noise-induced synaptopathy in this cohort, despite a wide range of exposures. In young adults with normal audiograms, tinnitus may be related not to cochlear synaptopathy but to other effects of noise exposure.

Item Type:
Journal Article
Journal or Publication Title:
Hearing Research
Additional Information:
This is the author’s version of a work that was accepted for publication in Hearing Research. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Hearing Research, ??, ?, 2016 DOI: 10.1016/j.heares.2016.12.002
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/2800/2809
Subjects:
ID Code:
83555
Deposited By:
Deposited On:
12 Dec 2016 09:28
Refereed?:
Yes
Published?:
Published
Last Modified:
24 Sep 2020 03:10