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Lobdell A, Trujillo T, Jennings SG. Assessment of Cochlear Synaptopathy with Standard Clinical Equipment. J Am Acad Audiol 2024. [PMID: 39242092 DOI: 10.1055/s-0042-1758530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/09/2024]
Abstract
BACKGROUND Tinnitus, hyperacusis, and difficulties listening in background noise may be associated with the loss of auditory nerve fibers known as the condition of cochlear synaptopathy. Multiple research-based tests of auditory function have been developed to identify the potential for synaptopathy in animals and humans, including assessment of the middle-ear muscle reflex (MEMR). Despite these research-based tests, there is no verified method for measuring or identifying the potential for cochlear synaptopathy using standard audiologic equipment. PURPOSE The goal of this study was to determine if commonly used audiometric equipment could be configured in a way that approximated the test methods used in the research environment, making it a viable tool in the assessment of patients who present with symptoms consistent with cochlear synaptopathy (tinnitus, hyperacusis, speech-in-noise difficulties). METHODS Laboratory-based and clinically based measures of MEMR strength-as estimated from changes in probe pressure/admittance in response to contralateral noise-were compared for 20 subjects. MEMR strength estimated from laboratory equipment increased with increasing intensity of the contralateral noise elicitor. RESULTS AND CONCLUSIONS A moderate positive correlation was found between laboratory- and clinically based measures of MEMR strength. This correlation supports the hypothesis that commonly used clinical equipment can be employed to assess the potential for cochlear synaptopathy in patients who present with the associated symptoms.
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Affiliation(s)
- Anne Lobdell
- Department of Communication Sciences and Disorders, The University of Utah, Salt Lake City, Utah
| | - Tevan Trujillo
- Department of Communication Sciences and Disorders, The University of Utah, Salt Lake City, Utah
| | - Skyler G Jennings
- Department of Communication Sciences and Disorders, The University of Utah, Salt Lake City, Utah
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2
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Anastasios G, Magioula G, Konstantinos K, Ioannis A. Noise and Health: Review. Indian J Otolaryngol Head Neck Surg 2022; 74:5482-5491. [PMID: 36742745 PMCID: PMC9895353 DOI: 10.1007/s12070-021-02797-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Accepted: 08/01/2021] [Indexed: 02/07/2023] Open
Abstract
Noise in human societies is unavoidable, but it tends to become a modern epidemic that induces various detrimental effects to several organs and functions in humans. Increased cardiovascular danger, anxiety and sleep disturbance are just few of these effects. It is noteworthy that children, even neonates and their developing organism are especially vulnerable to noise-related health problems. Noise is measured with special noise-meters. These devices express results in decibels by transforming random noise to a continuous sound. This sound is characterized by equivalent acoustic energy to the random noise for a defined time interval. Human auditory apparatus is principally endangered by acute noises but also by chronic noise exposure, in the context of both occupational and recreational activities. Various mechanisms are implicated in the pathogenesis of noise-induced hearing loss that can cause either temporary or permanent damage. Among them, emphasis is given to the impairment by free radicals and inflammatory mediators, to the activation of apoptotic molecular pathways, but also to glutamate excitotoxicity. A hidden hearing loss, synaptopathy, is attributed to the latter. The irreversible nature of hearing loss, as well as the idiosyncratic sensitivity of individuals, imposes the necessity of early diagnosis of auditory impairment by noise. Super high frequency audiograms, otoacoustic emissions and electrophysiological examinations can address diagnosis. Thankfully, there is extensive research on acoustic trauma therapeutic approaches. However, until we succeed in regenerating the sensory organ of hearing, chronic noise-induced hearing loss cannot be treated. Thus, it is fundamental that society protects people from noise, by laws and regulations.
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Affiliation(s)
- Goulioumis Anastasios
- Department of Otorhinolaryngology, Pediatric Hospital “Karamandanio”, Patras, Greece
| | | | - Kourelis Konstantinos
- Department of Otorhinolaryngology, Pediatric Hospital “Karamandanio”, Patras, Greece
| | - Athanasopoulos Ioannis
- Department of Otorhinolaryngology, Pediatric Center of “Iatriko Athinon” Hospital, Athens, Greece
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3
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Cross-species experiments reveal widespread cochlear neural damage in normal hearing. Commun Biol 2022; 5:733. [PMID: 35869142 PMCID: PMC9307777 DOI: 10.1038/s42003-022-03691-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Accepted: 07/08/2022] [Indexed: 11/24/2022] Open
Abstract
Animal models suggest that cochlear afferent nerve endings may be more vulnerable than sensory hair cells to damage from acoustic overexposure and aging. Because neural degeneration without hair-cell loss cannot be detected in standard clinical audiometry, whether such damage occurs in humans is hotly debated. Here, we address this debate through co-ordinated experiments in at-risk humans and a wild-type chinchilla model. Cochlear neuropathy leads to large and sustained reductions of the wideband middle-ear muscle reflex in chinchillas. Analogously, human wideband reflex measures revealed distinct damage patterns in middle age, and in young individuals with histories of high acoustic exposure. Analysis of an independent large public dataset and additional measurements using clinical equipment corroborated the patterns revealed by our targeted cross-species experiments. Taken together, our results suggest that cochlear neural damage is widespread even in populations with clinically normal hearing. Cross-species experiments on chinchillas and at-risk humans suggest cochlear synaptopathy from noise exposure and aging are widespread even among individuals with clinically normal hearing status.
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Swallow J, Fedele E, Sallis-Peterson F. Modeling Injury Risk From Multiple-Impulse, Area-Distributed Flash-bangs Using an Uncertainty Bounding Approach to Dose Accumulation. Mil Med 2022; 188:usac083. [PMID: 35451004 DOI: 10.1093/milmed/usac083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2021] [Revised: 01/16/2022] [Accepted: 04/19/2022] [Indexed: 11/13/2022] Open
Abstract
INTRODUCTION Modeling of injury risk from nonlethal weapons including flash-bangs is a critical step in the design, acquisition, and application of such devices for military purposes. One flash-bang design concept currently being developed involves multiple, area-distributed flash-bangs. It is particularly difficult to model the variation inherent in operational settings employing such devices due to the randomness of flash-bang detonation positioning relative to targets. The problem is exacerbated by uncertainty related to changes in the mechanical properties of auditory system tissues and contraction of muscles in the middle ear (the acoustic reflex), which can both immediately follow impulse-noise exposure. In this article, we demonstrate a methodology to quantify uncertainty in injury risk estimation related to exposure to multiple area-distributed flash-bang impulses in short periods of time and analyze the effects of factors such as the number of impulses, their spatial distribution, and the uncertainties in their parameters on estimated injury risk. MATERIALS AND METHODS We conducted Monte Carlo simulations of dispersion and timing of a mortar-and-submunition flash-bang device that distributes submunitions over an area, using the Auditory 4.5 model developed by L3 Applied Technologies to estimate the risk of hearing loss (permanent threshold shift) in an exposure area. We bound injury risk estimates by applying limiting assumptions for dose accumulation rules applied to short inter-pulse intervals and varied impulse-noise-intensity exposure characteristic of multi-impulse flash-bangs. The upper bound of risk assumes no trading of risk between the number of impulses and intensity of individual impulses, while the lower bound assumes a perfectly protective acoustic reflex. RESULTS In general, the risk to individuals standing in the most hazardous zone of the simulation is quite sensitive to the pattern of submunitions, relative to the sensitivity for those standing farther from that zone. Larger mortar burst radii (distributing submunitions over a wider area) reduce expected peak risk, while increasing the number of submunitions, the intensity of individual impulses, or the uncertainty in impulse intensity increases expected risk. We find that injury risk calculations must factor in device output variation because the injury risk curve in the flash-bang dose regime is asymmetric. We also find that increased numbers of submunitions increase the peak risk in an area more rapidly than scene-averaged risk and that the uncertainty related to dose accumulation in the acoustic reflex regime can be substantial for large numbers of submunitions and should not be ignored. CONCLUSIONS This work provides a methodology for exploring both the role of device parameters and the choice of dose accumulation rule in estimating the risk of significant injury and associated uncertainty for multi-impulse, area-distributed flash-bang exposures. This analysis can inform decisions about the design of flash-bangs and training for their operational usage. The methodology can be extended to other device designs or deployment concepts to generate risk maps and injury risk uncertainty ranges. This work does not account for additional injury types beyond permanent threshold shift that may occur as a result of flash-bang exposure. A useful extension of this work would be similar work connecting design and operational parameters to human effectiveness.
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Affiliation(s)
- Jessica Swallow
- Science and Technology Division, Institute for Defense Analyses, Alexandria, VA 22305, USA
| | - Emily Fedele
- Science and Technology Division, Institute for Defense Analyses, Alexandria, VA 22305, USA
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5
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Neave-DiToro D, Bergen M, Silman S, Emmer MB. Presence of ipsilateral acoustic reflex artifact may result in clinical misidentification. Int J Audiol 2021; 61:437-440. [PMID: 34106808 DOI: 10.1080/14992027.2021.1931486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
OBJECTIVE Upon calibration of a specific commercially available immittance device, an artifact was consistently measured in a calibration cavity when in ipsilateral acoustic reflex mode. These results were replicated in a controlled fashion, raising concerns about how clinical results might potentially be misinterpreted. DESIGN Responses were measured from an Interacoustics Titan and Grason-Stadler Tympstar Pro immittance device coupled to a 0.2 cc and, separately, to a 1.0 cc calibration cavity when in ipsilateral acoustic reflex mode. The procedure was repeated with the same outcomes. RESULTS Clinically significant responses ordinarily associated with presence of an ipsilateral acoustic reflex were obtained in a 0.2 cc and 1 cc coupler with stimuli presented at 0.5 kHz, 1 kHz, and 2 kHz with one of the Interacoustics Titan, but were not obtained in the same conditions with the Grason-Stadler Tympstar Pro. CONCLUSIONS A commercially available immittance device yielded clinically-significant responses to ipsilateral acoustic reflex stimuli within calibration cavities of various sizes. Results suggest that false-positive responses may be obtained when certain immittance devices are used clinically, producing possible misleading or incorrect clinical impressions and assessment.
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Affiliation(s)
- Dorothy Neave-DiToro
- Department of Communication Arts, Sciences, and Disorders, Brooklyn College, City University of New York (CUNY), Brooklyn, NY, USA.,Doctor of Audiology Program, Graduate Center, CUNY, New York, NY, USA
| | - Michael Bergen
- Department of Communication Arts, Sciences, and Disorders, Brooklyn College, City University of New York (CUNY), Brooklyn, NY, USA.,Doctor of Audiology Program, Graduate Center, CUNY, New York, NY, USA
| | - Shlomo Silman
- Department of Communication Arts, Sciences, and Disorders, Brooklyn College, City University of New York (CUNY), Brooklyn, NY, USA.,Doctor of Audiology Program, Graduate Center, CUNY, New York, NY, USA.,Speech-Language-Hearing Sciences, Graduate Center, CUNY, New York, NY, USA
| | - Michele B Emmer
- Department of Communication Arts, Sciences, and Disorders, Brooklyn College, City University of New York (CUNY), Brooklyn, NY, USA.,Doctor of Audiology Program, Graduate Center, CUNY, New York, NY, USA
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6
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Casazza GC, Gray LC, Hildebrand D, Kesser BW. Acoustic Reflexes in Aural Atresia Patients: Evidence of an Intact Efferent System? Ann Otol Rhinol Laryngol 2021; 130:1004-1009. [PMID: 33491463 DOI: 10.1177/0003489421990168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
OBJECTIVE To record crossed acoustic reflex thresholds (xART's) postoperatively from patients after surgical repair of unilateral congenital aural atresia (CAA). To seek explanations for when xARTs can and cannot be recorded. We hope to understand the implications for this central auditory reflex despite early afferent deprivation. METHODS Patients who underwent surgery to correct unilateral CAA at a tertiary academic medical were prospectively enrolled to evaluate for the presence of xART. Preoperative ARTs in the normal (non-atretic) ear, and postoperative ipsilateral ARTs (stimulus in the normal ear) and contralateral ARTs (stimulus in the newly reconstructed atretic ear; record in the normal ear) were measured at 500, 1000, and 2000 Hz. RESULTS Four of 11 patients with normal ipsilateral reflex thresholds preoperatively demonstrated crossed acoustic reflexes postoperatively (stimulus in reconstructed ear; record from normal ear). Four other patients demonstrated normal ipsilateral thresholds preoperatively but did not have crossed reflexes postoperatively. No reflexes (pre- or postoperatively) could be recorded in 3 patients. Crossed reflex threshold is significantly correlated with the postoperative audiometric threshold. There was no correlation between ipsilateral and contralateral reflex thresholds. CONCLUSION Crossed acoustic reflexes can be recorded from some but not all postoperative atresia patients, and the thresholds for those reflexes correlate with the postoperative pure tone threshold. The presence of acoustic reflexes implies an intact CN VIII-to-opposite CN VII central reflex arc despite early unilateral sound deprivation.
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Affiliation(s)
- Geoffrey C Casazza
- Department of Otolaryngology-Head and Neck Surgery, University of Virginia, Charlottesville, VA, USA
| | - Lincoln C Gray
- Department of Otolaryngology-Head and Neck Surgery, University of Virginia, Charlottesville, VA, USA.,Department of Communication Sciences and Disorders, James Madison University, Harrisonburg, VA, USA
| | - Debra Hildebrand
- Department of Otolaryngology-Head and Neck Surgery, University of Virginia, Charlottesville, VA, USA
| | - Bradley W Kesser
- Department of Otolaryngology-Head and Neck Surgery, University of Virginia, Charlottesville, VA, USA
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7
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Aedo C, Aguilar E. Cochlear synaptopathy: new findings in animal and human research. Rev Neurosci 2020; 31:605-615. [PMID: 32681786 DOI: 10.1515/revneuro-2020-0002] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Accepted: 04/25/2020] [Indexed: 12/30/2022]
Abstract
In animal models, prolonged exposure (2 h) to high-level noise causes an irreparable damage to the synapses between the inner hair cells and auditory nerve fibers within the cochlea. Nevertheless, this injury does not necessarily alter the hearing threshold. Similar findings have been observed as part of typical aging in animals. This type of cochlear synaptopathy, popularly called "hidden hearing loss," has been a significant issue in neuroscience research and clinical audiology scientists. The results obtained in different investigations are inconclusive in their diagnosis and suggest new strategies for both prognosis and treatment of cochlear synaptopathy. Here we review the major physiological findings regarding cochlear synaptopathy in animals and humans and discuss mathematical models. We also analyze the potential impact of these results on clinical practice and therapeutic options.
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Affiliation(s)
- Cristian Aedo
- Laboratorio de Audiología y Percepción Auditiva, Facultad de Medicina, Universidad de Chile, Santiago, 8380453, Chile
- Departamento de Tecnología Médica, Facultad de Medicina, Universidad de Chile, Santiago, 8380453, Chile
| | - Enzo Aguilar
- Laboratorio de Audiología y Percepción Auditiva, Facultad de Medicina, Universidad de Chile, Santiago, 8380453, Chile
- Departamento de Tecnología Médica, Facultad de Medicina, Universidad de Chile, Santiago, 8380453, Chile
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8
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Nakashima A, Giguère C. Toward an improved hearing safety standard for impulse noise exposure in the Canadian Armed Forces. JOURNAL OF MILITARY VETERAN AND FAMILY HEALTH 2020. [DOI: 10.3138/jmvfh-2019-0035] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Introduction: Current hearing safety standards for the Canadian Armed Forces (CAF) do not adequately address exposure limits for mitigation of noise-induced hearing loss (NIHL) from weapon noise. Recommendations for updating the hearing safety standard are being formulated by the recently initiated Noise Health Hazard Working Group (NHHWG). In this article, we aim to provide a way forward for the NHHWG. Methods: On the basis of experience with auditory research, noise measurement, acoustic standards development, interactions with CAF members, and a review of the literature, we present an overview of the current state of knowledge regarding impulse noise. The topics include impulse noise measurement, engineering and administrative controls for noise exposure, and use of personal hearing protection devices (HPDs). Results: Although technology for impulse noise measurements and ways to account for HPDs have improved substantially in recent years, not much has changed in hearing damage risk criteria. Energy-based metrics can account for the impulse duration and frequency-dependent characteristics of the HPD, which are important considerations in calculating allowed exposures. Discussion: The NHHWG is recommended to focus on measurements of current weapons systems in various configurations and training environments and to evaluate the use of energy-based metrics, together with frequency-dependent HPD insertion loss.
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Affiliation(s)
- Ann Nakashima
- Defence Research and Development Canada, Toronto Research Centre
| | - Christian Giguère
- Audiology and Speech-Language Pathology Program, University of Ottawa
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9
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Guest H, Munro KJ, Couth S, Millman RE, Prendergast G, Kluk K, Murray C, Plack C. No Effect of Interstimulus Interval on Acoustic Reflex Thresholds. Trends Hear 2020; 23:2331216519874165. [PMID: 31516095 PMCID: PMC6852360 DOI: 10.1177/2331216519874165] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The acoustic reflex (AR), a longstanding component of the audiological test battery, has received renewed attention in the context of noise-induced cochlear synaptopathy—the destruction of synapses between inner hair cells and auditory nerve fibers. Noninvasive proxy measures of synaptopathy are widely sought, and AR thresholds (ARTs) correlate closely with synaptic survival in rodents. However, measurement in humans at high stimulus frequencies—likely important when testing for noise-induced pathology—can be challenging; reflexes at 4 kHz are frequently absent or occur only at high stimulus levels, even in young people with clinically normal audiograms. This phenomenon may partly reflect differences across stimulus frequency in the temporal characteristics of the response; later onset of the response, earlier onset of adaptation, and higher rate of adaptation have been observed at 4 kHz than at 1 kHz. One temporal aspect of the response that has received little attention is the interstimulus interval (ISI); inadequate duration of ISI might lead to incomplete recovery of the response between successive presentations and consequent response fatigue. This research aimed to test for effects of ISI on ARTs in normally hearing young humans, measured at 1 and 4 kHz. Contrary to our hypotheses, increasing ISIs from 2.5 to 8.5 s did not reduce ART level, nor raise ART reliability. Results confirm that clinically measured ARTs—including those at 4 kHz—can exhibit excellent reliability and that relatively short (2.5 s) ISIs are adequate for the measurement of sensitive and reliable ARTs.
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Affiliation(s)
- Hannah Guest
- Manchester Centre for Audiology and Deafness, Manchester Academic Health Science Centre, University of Manchester, UK
| | - Kevin J Munro
- Manchester Centre for Audiology and Deafness, Manchester Academic Health Science Centre, University of Manchester, UK.,Manchester University NHS Foundation Trust, UK
| | - Samuel Couth
- Manchester Centre for Audiology and Deafness, Manchester Academic Health Science Centre, University of Manchester, UK
| | - Rebecca E Millman
- Manchester Centre for Audiology and Deafness, Manchester Academic Health Science Centre, University of Manchester, UK
| | - Garreth Prendergast
- Manchester Centre for Audiology and Deafness, Manchester Academic Health Science Centre, University of Manchester, UK
| | - Karolina Kluk
- Manchester Centre for Audiology and Deafness, Manchester Academic Health Science Centre, University of Manchester, UK
| | - Carlyn Murray
- Manchester Centre for Audiology and Deafness, Manchester Academic Health Science Centre, University of Manchester, UK
| | - Chris Plack
- Manchester Centre for Audiology and Deafness, Manchester Academic Health Science Centre, University of Manchester, UK.,Department of Psychology, Lancaster University, UK
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Themann CL, Masterson EA. Occupational noise exposure: A review of its effects, epidemiology, and impact with recommendations for reducing its burden. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2019; 146:3879. [PMID: 31795665 DOI: 10.1121/1.5134465] [Citation(s) in RCA: 108] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Exposure to hazardous noise is one of the most common occupational risks, both in the U.S. and worldwide. Repeated overexposure to noise at or above 85 dBA can cause permanent hearing loss, tinnitus, and difficulty understanding speech in noise. It is also associated with cardiovascular disease, depression, balance problems, and lower income. About 22 million U.S. workers are currently exposed to hazardous occupational noise. Approximately 33% of working-age adults with a history of occupational noise exposure have audiometric evidence of noise-induced hearing damage, and 16% of noise-exposed workers have material hearing impairment. While the Mining, Construction, and Manufacturing sectors typically have the highest prevalence of noise exposure and hearing loss, there are noise-exposed workers in every sector and every sector has workers with hearing loss. Noise-induced hearing loss is preventable. Increased understanding of the biological processes underlying noise damage may lead to protective pharmacologic or genetic therapies. For now, an integrated public health approach that (1) emphasizes noise control over reliance on hearing protection, (2) illustrates the full impact of hearing loss on quality of life, and (3) challenges the cultural acceptance of loud noise can substantially reduce the impact of noise on worker health.
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Affiliation(s)
- Christa L Themann
- National Institute for Occupational Safety and Health, 1090 Tusculum Avenue, MS C-27, Cincinnati, Ohio 45226, USA
| | - Elizabeth A Masterson
- National Institute for Occupational Safety and Health, 1090 Tusculum Avenue, MS C-27, Cincinnati, Ohio 45226, USA
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11
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Le Prell CG, Hammill TL, Murphy WJ. Noise-induced hearing loss and its prevention: Integration of data from animal models and human clinical trials. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2019; 146:4051. [PMID: 31795668 PMCID: PMC7195863 DOI: 10.1121/1.5132951] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 10/19/2019] [Indexed: 05/07/2023]
Abstract
Animal models have been used to gain insight into the risk of noise-induced hearing loss (NIHL) and its potential prevention using investigational new drug agents. A number of compounds have yielded benefit in pre-clinical (animal) models. However, the acute traumatic injury models commonly used in pre-clinical testing are fundamentally different from the chronic and repeated exposures experienced by many human populations. Diverse populations that are potentially at risk and could be considered for enrollment in clinical studies include service members, workers exposed to occupational noise, musicians and other performing artists, and children and young adults exposed to non-occupational (including recreational) noise. Both animal models and clinical populations were discussed in this special issue, followed by discussion of individual variation in vulnerability to NIHL. In this final contribution, study design considerations for NIHL otoprotection in pre-clinical and clinical testing are integrated and broadly discussed with evidence-based guidance offered where possible, drawing on the contributions to this special issue as well as other existing literature. The overarching goals of this final paper are to (1) review and summarize key information across contributions and (2) synthesize information to facilitate successful translation of otoprotective drugs from animal models into human application.
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Affiliation(s)
- Colleen G Le Prell
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Dallas, Texas 75080, USA
| | - Tanisha L Hammill
- Department of Defense, Defense Health Agency, Falls Church, Virginia 22042, USA
| | - William J Murphy
- Division of Field Studies and Engineering, National Institute for Occupational Safety and Health, Cincinanati, Ohio 45226-1998, USA
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12
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Deiters KK, Flamme GA, Tasko SM, Murphy WJ, Greene NT, Jones HG, Ahroon WA. Generalizability of clinically measured acoustic reflexes to brief sounds. THE JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA 2019; 146:3993. [PMID: 31795698 PMCID: PMC7043895 DOI: 10.1121/1.5132705] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Revised: 08/20/2019] [Accepted: 08/22/2019] [Indexed: 05/08/2023]
Abstract
Middle ear muscle contractions (MEMC) can be elicited in response to high-level sounds, and have been used clinically as acoustic reflexes (ARs) during evaluations of auditory system integrity. The results of clinical AR evaluations do not necessarily generalize to different signal types or durations. The purpose of this study was to evaluate the likelihood of observing MEMC in response to brief sound stimuli (tones, recorded gunshots, noise) in adult participants (N = 190) exhibiting clinical ARs and excellent hearing sensitivity. Results revealed that the presence of clinical ARs was not a sufficient indication that listeners will also exhibit MEMC for brief sounds. Detection rates varied across stimulus types between approximately 20% and 80%. Probabilities of observing MEMC also differed by clinical AR magnitude and latency, and declined over the period of minutes during the course of the MEMC measurement series. These results provide no support for the inclusion of MEMC as a protective factor in damage-risk criteria for impulsive noises, and the limited predictability of whether a given individual will exhibit MEMC in response to a brief sound indicates a need to measure and control for MEMC in studies evaluating pharmaceutical interventions for hearing loss.
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Affiliation(s)
- Kristy K Deiters
- Stephenson and Stephenson Research and Consulting (SASRAC), Forest Grove, Oregon 97116, USA
| | - Gregory A Flamme
- Stephenson and Stephenson Research and Consulting (SASRAC), Forest Grove, Oregon 97116, USA
| | - Stephen M Tasko
- Stephenson and Stephenson Research and Consulting (SASRAC), Forest Grove, Oregon 97116, USA
| | - William J Murphy
- National Institute for Occupational Safety and Health (NIOSH), Cincinnati, Ohio 45226, USA
| | - Nathaniel T Greene
- United States (U.S.) Army Aeromedical Research Lab (USAARL), Fort Rucker, Alabama 36362, USA
| | - Heath G Jones
- United States (U.S.) Army Aeromedical Research Lab (USAARL), Fort Rucker, Alabama 36362, USA
| | - William A Ahroon
- United States (U.S.) Army Aeromedical Research Lab (USAARL), Fort Rucker, Alabama 36362, USA
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13
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Bramhall N, Beach EF, Epp B, Le Prell CG, Lopez-Poveda EA, Plack CJ, Schaette R, Verhulst S, Canlon B. The search for noise-induced cochlear synaptopathy in humans: Mission impossible? Hear Res 2019; 377:88-103. [DOI: 10.1016/j.heares.2019.02.016] [Citation(s) in RCA: 74] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 02/25/2019] [Accepted: 02/28/2019] [Indexed: 10/27/2022]
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14
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Le Prell CG. Effects of noise exposure on auditory brainstem response and speech-in-noise tasks: a review of the literature. Int J Audiol 2018; 58:S3-S32. [DOI: 10.1080/14992027.2018.1534010] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Colleen G. Le Prell
- School of Behavioral and Brain Sciences, University of Texas at Dallas, Dallas, TX, USA
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15
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Jones HG, Greene NT, Ahroon WA. Human middle-ear muscles rarely contract in anticipation of acoustic impulses: Implications for hearing risk assessments. Hear Res 2018; 378:53-62. [PMID: 30538053 DOI: 10.1016/j.heares.2018.11.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Revised: 11/14/2018] [Accepted: 11/16/2018] [Indexed: 12/30/2022]
Abstract
The current study addressed the existence of an anticipatory middle-ear muscle contraction (MEMC) as a protective mechanism found in recent damage-risk criteria for impulse noise exposure. Specifically, the experiments reported here tested instances when an exposed individual was aware of and could anticipate the arrival of an acoustic impulse. In order to detect MEMCs in human subjects, a laser-Doppler vibrometer (LDV) was used to measure tympanic membrane (TM) motion in response to a probe tone. Here we directly measured the time course and relative magnitude changes of TM velocity in response to an acoustic reflex-eliciting (i.e. MEMC eliciting) impulse in 59 subjects with clinically assessable MEMCs. After verifying the presence of the MEMC, we used a classical conditioning paradigm pairing reflex-eliciting acoustic impulses (unconditioned stimulus, UCS) with various preceding stimuli (conditioned stimulus, CS). Changes in the time-course of the MEMC following conditioning were considered evidence of MEMC conditioning, and any indication of an MEMC prior to the onset of the acoustic elicitor was considered an anticipatory response. Nine subjects did not produce a MEMC measurable via LDV. For those subjects with an observable MEMC (n = 50), 48 subjects (96%) did not show evidence of an anticipatory response after conditioning, whereas only 2 subjects (4%) did. These findings reveal that MEMCs are not readily conditioned in most individuals, suggesting that anticipatory MEMCs are not prevalent within the general population. The prevalence of anticipatory MEMCs does not appear to be sufficient to justify inclusion as a protective mechanism in auditory injury risk assessments.
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Affiliation(s)
- Heath G Jones
- United States Army Aeromedical Research Laboratory, 6901 Farrel Road, Fort Rucker, AL, 36362, USA; Laulima Government Solutions, LLC, 12565 Research Parkway, Suite 300, Orlando, FL, 32826, USA.
| | - Nathaniel T Greene
- United States Army Aeromedical Research Laboratory, 6901 Farrel Road, Fort Rucker, AL, 36362, USA; The Geneva Foundation, 917 Pacific Ave, Suite 600, Tacoma, WA, 98402, USA.
| | - William A Ahroon
- United States Army Aeromedical Research Laboratory, 6901 Farrel Road, Fort Rucker, AL, 36362, USA.
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16
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Intracochlear pressure measurements during acoustic shock wave exposure. Hear Res 2018; 365:149-164. [PMID: 29843947 DOI: 10.1016/j.heares.2018.05.014] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 05/02/2018] [Accepted: 05/17/2018] [Indexed: 11/20/2022]
Abstract
INTRODUCTION Injuries to the peripheral auditory system are among the most common results of high intensity impulsive acoustic exposure. Prior studies of high intensity sound transmission by the ossicular chain have relied upon measurements in animal models, measurements at more moderate sound levels (i.e. < 130 dB SPL), and/or measured responses to steady-state noise. Here, we directly measure intracochlear pressure in human cadaveric temporal bones, with fiber optic pressure sensors placed in scala vestibuli (SV) and tympani (ST), during exposure to shock waves with peak positive pressures between ∼7 and 83 kPa. METHODS Eight full-cephalic human cadaver heads were exposed, face-on, to acoustic shock waves in a 45 cm diameter shock tube. Specimens were exposed to impulses with nominal peak overpressures of 7, 28, 55, & 83 kPa (171, 183, 189, & 192 dB pSPL), measured in the free field adjacent to the forehead. Specimens were prepared bilaterally by mastoidectomy and extended facial recess to expose the ossicular chain. Ear canal (EAC), middle ear, and intracochlear sound pressure levels were measured with fiber-optic pressure sensors. Surface-mounted sensors measured SPL and skull strain near the opening of each EAC and at the forehead. RESULTS Measurements on the forehead showed incident peak pressures approximately twice that measured by adjacent free-field and EAC entrance sensors, as expected based on the sensor orientation (normal vs tangential to the shock wave propagation). At 7 kPa, EAC pressure showed gain, calculated from the frequency spectra, consistent with the ear canal resonance, and gain in the intracochlear pressures (normalized to the EAC pressure) were consistent with (though somewhat lower than) previously reported middle ear transfer functions. Responses to higher intensity impulses tended to show lower intracochlear gain relative to EAC, suggesting sound transmission efficiency along the ossicular chain is reduced at high intensities. Tympanic membrane (TM) rupture was observed following nearly every exposure 55 kPa or higher. CONCLUSIONS Intracochlear pressures reveal lower middle-ear transfer function magnitudes (i.e. reduced gain relative to the ear canal) for high sound pressure levels, thus revealing lower than expected cochlear exposure based on extrapolation from cochlear pressures measured at more moderate sound levels. These results are consistent with lowered transmissivity of the ossicular chain at high intensities, and are consistent with our prior report measuring middle ear transfer functions in human cadaveric temporal bones with high intensity tone pips.
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17
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McGregor KD, Flamme GA, Tasko SM, Deiters KK, Ahroon WA, Themann CL, Murphy WJ. Acoustic reflexes are common but not pervasive: evidence using a diagnostic middle ear analyser. Int J Audiol 2018; 57:S42-S50. [PMID: 29256642 PMCID: PMC6719315 DOI: 10.1080/14992027.2017.1416189] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Accepted: 12/03/2017] [Indexed: 10/18/2022]
Abstract
OBJECTIVE The objective of this study is to determine whether acoustic reflexes are pervasive (i.e. known with 95% confidence to be observed in at least 95% of people) by examining the frequency of occurrence using a friction-fit diagnostic middle ear analyser. DESIGN Adult participants with very good hearing sensitivity underwent audiometric and middle ear testing. Acoustic reflexes were tested ipsilaterally and contralaterally in both ears across a range of elicitor frequencies. Reflex elicitors were 700 ms tones presented at maximum level of 100 dB HL. Two automated methods were used to detect the presence of an acoustic reflex. STUDY SAMPLE A group of 285 adult volunteers with normal hearing. RESULTS There were no conditions in which the proportion of participants exhibiting acoustic reflexes was high enough to be deemed pervasive. Ipsilateral reflexes were more likely to be observed than contralateral reflexes and reflexes were more common at 0.5 and 1 kHz elicitor frequencies as compared with 2 and 4 kHz elicitor frequencies. CONCLUSIONS Acoustic reflexes are common among individuals with good hearing. However, acoustic reflexes are not pervasive and should not be included in damage risk criteria and health hazard assessments for impulsive noise.
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Affiliation(s)
- Kara D. McGregor
- Department of Speech, Language and Hearing Sciences, Western Michigan University, 1903 W. Michigan Ave., Kalamazoo, MI 49008–5355
| | - Gregory A. Flamme
- Stephenson and Stephenson Research and Consulting, LLC, 2264 Heather Way, Forest Grove, OR USA
| | - Stephen M. Tasko
- Stephenson and Stephenson Research and Consulting, LLC, 2264 Heather Way, Forest Grove, OR USA
- Department of Speech, Language and Hearing Sciences, Western Michigan University, 1903 W. Michigan Ave., Kalamazoo, MI 49008–5355
| | - Kristy K. Deiters
- Stephenson and Stephenson Research and Consulting, LLC, 2264 Heather Way, Forest Grove, OR USA
| | - William A. Ahroon
- Auditory Protection and Performance Division, U.S. Army Aeromedical Research Laboratory, Building 6901, Farrel Road, Fort Rucker, AL 36362-0577
| | - Christa L. Themann
- Hearing Loss Prevention Team, Engineering and Physical Hazards Branch, Division of Applied Research and Technology, National Institute for Occupational Safety and Health, 1090 Tusculum Ave. Mailstop C-27, Cincinnati, OH USA
| | - William J. Murphy
- Hearing Loss Prevention Team, Engineering and Physical Hazards Branch, Division of Applied Research and Technology, National Institute for Occupational Safety and Health, 1090 Tusculum Ave. Mailstop C-27, Cincinnati, OH USA
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18
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Murphy WJ, Flamme GA, Campbell AR, Zechmann EL, Tasko SM, Lankford JE, Meinke DK, Finan DS, Stewart M. The reduction of gunshot noise and auditory risk through the use of firearm suppressors and low-velocity ammunition. Int J Audiol 2018; 57:S28-S41. [DOI: 10.1080/14992027.2017.1407459] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- William J. Murphy
- Hearing Loss Prevention Team, Engineering and Physical Hazards Branch, Division of Applied Research and Technology, National Institute for Occupational Safety and Health, Cincinnati, OH, USA,
| | - Gregory A. Flamme
- Stephenson and Stephenson Research and Consulting, LLC, Forest Grove, OR, USA,
| | - Adam R. Campbell
- Hearing Loss Prevention Team, Engineering and Physical Hazards Branch, Division of Applied Research and Technology, National Institute for Occupational Safety and Health, Cincinnati, OH, USA,
| | - Edward L. Zechmann
- Hearing Loss Prevention Team, Engineering and Physical Hazards Branch, Division of Applied Research and Technology, National Institute for Occupational Safety and Health, Cincinnati, OH, USA,
| | - Stephen M. Tasko
- Stephenson and Stephenson Research and Consulting, LLC, Forest Grove, OR, USA,
- Department of Speech, Language and Hearing Sciences, Western Michigan University, Kalamazoo, MI, USA,
| | - James E. Lankford
- Allied Health and Communication Disorders, Northern Illinois University, Dekalb, IL, USA,
| | - Deanna K. Meinke
- Audiology and Speech-Language Sciences, University of Northern Colorado, Greeley, CO, USA, and
| | - Donald S. Finan
- Audiology and Speech-Language Sciences, University of Northern Colorado, Greeley, CO, USA, and
| | - Michael Stewart
- Department of Communication Disorders, Central Michigan University, Mount Pleasant, MI, USA
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