Hidden hearing deficits in military service members with persistent post concussive symptoms

Abstract

Introduction: Individuals with persistent symptoms after mild traumatic brain injury (mTBI) often have auditory complaints. In this study, we used the auditory brainstem response (ABR) to determine whether cochlear synaptopathy could explain auditory symptoms. Methods: 69 adult military service members with mTBI and 25 adults without brain injury (NCT01611194 and NCT01925963) completed pure-tone audiometry, ABR, and central auditory processing tests. All participants were male, ages 21-50. Results: 37/69 mTBI participants had measurable hearing loss, while another 20-30% had hearing complaints or tinnitus. While mTBI participants with measurable hearing loss had reduced wave I and III amplitude and decreased III-V interpeak latency, those with no measurable hearing loss did not significantly differ from controls on any ABR parameter. Those with measurable hearing loss were also more likely to have abnormal central auditory processing. mTBI participants with no measurable hearing loss but who reported hearing concerns had some ABR findings (III-V interpeak latency, I and V amplitudes, V/I amplitude ratio) more like the measurable hearing loss mTBI group than normative controls. Conclusion: Cochlear synaptopathy may have contributed to some of the auditory impairment in service members with mTBI with measurable hearing loss. However, these results are likely confounded by cochlear hair cell damage.

Synaptopathy in Guinea Pigs Induced by Noise Mimicking Human Experience and Associated Changes in Auditory Signal Processing

“…However, this study did not measure synaptic loss and several technical limitations make it difficult to interpret the result [see our review ( Chen et al, 2019a ) for details]. In human studies, reports with negative results ( Fulbright et al, 2017 ; Grinn et al, 2017 ; Grose et al, 2017 ; Le Prell and Clavier, 2017 ; Prendergast et al, 2017a , 2019 ; Yeend et al, 2017 ; Guest et al, 2018 , 2019 ; Valderrama et al, 2018 ) have been more plentiful than those with positive results ( Alvord, 1983 ; Kujala et al, 2004 ; Stone et al, 2008 ; Kumar et al, 2012 ; Stamper and Johnson, 2015 ; Liberman et al, 2016 ; Tepe et al, 2017 ; Meehan et al, 2019 ). The variability in results could be partially rooted in methodological error or measurement inconsistency, including imprecise quantification of noise exposure based on different types of self-report, a lack of objective measurement of synaptic loss or its functional consequences, and different approaches to measuring CIND [see our recent review for detail ( Ripley et al, 2022 )].…”

Animal-to-Human Translation Difficulties and Problems With Proposed Coding-in-Noise Deficits in Noise-Induced Synaptopathy and Hidden Hearing Loss

“…In human subjects with histories of noise exposure but normal hearing thresholds, there is a lack of consensus concerning the existence of CIND or hearing-in-noise (HIN) problems as well as a lack of morphological evidence and functional data indicating loss or damage of ribbon synapses. There exist many negative publications ( Fulbright et al, 2017 ; Grinn et al, 2017 ; Grose et al, 2017 ; Le Prell and Clavier, 2017 ; Prendergast et al, 2017a , 2019 ; Yeend et al, 2017 ; Guest et al, 2018 , 2019a ; Valderrama et al, 2018 ), while positive reports are also available ( Alvord, 1983 ; Kujala et al, 2004 ; Stone et al, 2008 ; Kumar et al, 2012 ; Stamper and Johnson, 2015 ; Liberman et al, 2016 ; Tepe et al, 2017 ; Meehan et al, 2019 ). For example, the study by Grinn et al (2017) looked at the effects of long-term self-reported noise exposure as well as a loud recreational event on several audiologic measurements including ECochG.…”

Data_Sheet_1.docx

“…The CAP amplitude was measured between "x" symbols (A). Tepe et al, 2017;Meehan et al, 2019). The variability in results could be partially rooted in methodological error or measurement inconsistency, including imprecise quantification of noise exposure based on different types of self-report, a lack of objective measurement of synaptic loss or its functional consequences, and different approaches to measuring CIND [see our recent review for detail (Ripley et al, 2022)].…”