Auditory brainstem response to paired clicks as a candidate marker of cochlear synaptopathy in humans.

OBJECTIVE: This study aimed to evaluate whether auditory brainstem response (ABR) using a paired-click stimulation paradigm could serve as a tool for detecting cochlear synaptopathy (CS). METHODS: The ABRs to single-clicks and paired-clicks with various inter-click intervals (ICIs) and scores for word intelligibility in degraded listening conditions were obtained from 57 adults with normal hearing. The wave I peak amplitude and root mean square values for the post-wave I response within a range delayed from the wave I peak (referred to as the RMSpost-w1) were calculated for the single- and second-click responses. RESULTS: The wave I peak amplitudes did not correlate with age except for the second-click responses at an ICI of 7 ms, and the word intelligibility scores. However, we found that the RMSpost-w1 values for the second-click responses significantly decreased with increasing age. Moreover, the RMSpost-w1 values for the second-click responses at an ICI of 5 ms correlated significantly with the scores for word intelligibility in degraded listening conditions. CONCLUSIONS: The magnitude of the post-wave I response for the second-click response could serve as a tool for detecting CS in humans. SIGNIFICANCE: Our findings shed new light on the analytical methods of ABR for quantifying CS.

A genome-wide association study reveals a polygenic architecture of speech-in-noise deficits in individuals with self-reported normal hearing.

Speech-in-noise (SIN) perception is a primary complaint of individuals with audiometric hearing loss. SIN performance varies drastically, even among individuals with normal hearing. The present genome-wide association study (GWAS) investigated the genetic basis of SIN deficits in individuals with self-reported normal hearing in quiet situations. GWAS was performed on 279,911 individuals from the UB Biobank cohort, with 58,847 reporting SIN deficits despite reporting normal hearing in quiet. GWAS identified 996 single nucleotide polymorphisms (SNPs), achieving significance (p < 5*10-8) across four genomic loci. 720 SNPs across 21 loci achieved suggestive significance (p < 10-6). GWAS signals were enriched in brain tissues, such as the anterior cingulate cortex, dorsolateral prefrontal cortex, entorhinal cortex, frontal cortex, hippocampus, and inferior temporal cortex. Cochlear cell types revealed no significant association with SIN deficits. SIN deficits were associated with various health traits, including neuropsychiatric, sensory, cognitive, metabolic, cardiovascular, and inflammatory conditions. A replication analysis was conducted on 242 healthy young adults. Self-reported speech perception, hearing thresholds (0.25-16 kHz), and distortion product otoacoustic emissions (1-16 kHz) were utilized for the replication analysis. 73 SNPs were replicated with a self-reported speech perception measure. 211 SNPs were replicated with at least one and 66 with at least two audiological measures. 12 SNPs near or within MAPT, GRM3, and HLA-DQA1 were replicated for all audiological measures. The present study highlighted a polygenic architecture underlying SIN deficits in individuals with self-reported normal hearing.

The role of hidden hearing loss in tinnitus: Insights from early markers of peripheral hearing damage.

Since the presence of tinnitus is not always associated with audiometric hearing loss, it has been hypothesized that hidden hearing loss may act as a potential trigger for increased central gain along the neural pathway leading to tinnitus perception. In recent years, the study of hidden hearing loss has improved with the discovery of cochlear synaptopathy and several objective diagnostic markers. This study investigated three potential markers of peripheral hidden hearing loss in subjects with tinnitus: extended high-frequency audiometric thresholds, the auditory brainstem response, and the envelope following response. In addition, speech intelligibility was measured as a functional outcome measurement of hidden hearing loss. To account for age-related hidden hearing loss, participants were grouped according to age, presence of tinnitus, and audiometric thresholds. Group comparisons were conducted to differentiate between age- and tinnitus-related effects of hidden hearing loss. All three markers revealed age-related differences, whereas no differences were observed between the tinnitus and non-tinnitus groups. However, the older tinnitus group showed improved performance on low-pass filtered speech in noise tests compared to the older non-tinnitus group. These low-pass speech in noise scores were significantly correlated with tinnitus distress, as indicated using questionnaires, and could be related to the presence of hyperacusis. Based on our observations, cochlear synaptopathy does not appear to be the underlying cause of tinnitus. The improvement in low-pass speech-in-noise could be explained by enhanced temporal fine structure encoding or hyperacusis. Therefore, we recommend that future tinnitus research takes into account age-related factors, explores low-frequency encoding, and thoroughly assesses hyperacusis.

The curvature quantification of wave I in auditory brainstem responses detects cochlear synaptopathy in human beings.

PURPOSE: Patients with age-related hearing loss complain often about reduced speech perception in adverse listening environment. Studies on animals have suggested that cochlear synaptopathy may be one of the primary mechanisms responsible for this phenomenon. A decreased wave I amplitude in supra-threshold auditory brainstem response (ABR) can diagnose this pathology non-invasively. However, the interpretation of the wave I amplitude in humans remains controversial. Recent studies in mice have established a robust and reliable mathematic algorithm, i.e., curve curvature quantification, for detecting cochlear synaptopathy. This study aimed to determine whether the curve curvature has sufficient test-retest reliability to detect cochlear synaptopathy in aging humans. METHODS: Healthy participants were recruited into this prospective study. All subjects underwent an audiogram examination with standard and extended high frequencies ranging from 0.125 to 16 kHz and an ABR with a stimulus of 80 dB nHL click. The peak amplitude, peak latency, curvature at the peak, and the area under the curve of wave I were calculated and analyzed. RESULTS: A total of 80 individuals with normal hearing, aged 18 to 61 years, participated in this study, with a mean age of 26.4 years. Pearson correlation analysis showed a significant negative correlation between curvature and age, as well as between curvature and extended high frequency (EHF) threshold (10-16 kHz). Additionally, the same correlation was observed between age and area as well as age and EHF threshold. The model comparison demonstrated that the curvature at the peak of wave I is the best metric to correlate with EHF threshold. CONCLUSION: The curvature at the peak of wave I is the most sensitive metric for detecting cochlear synaptopathy in humans  and may be applied in routine diagnostics to detect early degenerations of the auditory nerve.

Effects of age and noise exposure history on auditory nerve response amplitudes: A systematic review, study, and meta-analysis.

Auditory nerve (AN) function has been hypothesized to deteriorate with age and noise exposure. Here, we perform a systematic review of published studies and find that the evidence for age-related deficits in AN function is largely consistent across the literature, but there are inconsistent findings among studies of noise exposure history. Further, evidence from animal studies suggests that the greatest deficits in AN response amplitudes are found in noise-exposed aged mice, but a test of the interaction between effects of age and noise exposure on AN function has not been conducted in humans. We report a study of our own examining differences in the response amplitude of the compound action potential N1 (CAP N1) between younger and older adults with and without a self-reported history of noise exposure in a large sample of human participants (63 younger adults 18-30 years of age, 103 older adults 50-86 years of age). CAP N1 response amplitudes were smaller in older than younger adults. Noise exposure history did not appear to predict CAP N1 response amplitudes, nor did the effect of noise exposure history interact with age. We then incorporated our results into two meta-analyses of published studies of age and noise exposure history effects on AN response amplitudes in neurotypical human samples. The meta-analyses found that age effects across studies are robust (r = -0.407), but noise exposure effects are weak (r = -0.152). We conclude that noise exposure effects may be highly variable depending on sample characteristics, study design, and statistical approach, and researchers should be cautious when interpreting results. The underlying pathology of age-related and noise-induced changes in AN function are difficult to determine in living humans, creating a need for longitudinal studies of changes in AN function across the lifespan and histological examination of the AN from temporal bones collected post-mortem.

Effects of Age and Noise Exposure History on Auditory Nerve Response Amplitudes: A Systematic Review, Study, and Meta-Analysis.

Auditory nerve (AN) function has been hypothesized to deteriorate with age and noise exposure. Here, we perform a systematic review of published studies and find that the evidence for age-related deficits in AN function is largely consistent across the literature, but there are inconsistent findings among studies of noise exposure history. Further, evidence from animal studies suggests that the greatest deficits in AN response amplitudes are found in noise-exposed aged mice, but a test of the interaction between effects of age and noise exposure on AN function has not been conducted in humans. We report a study of our own examining differences in the response amplitude of the compound action potential N1 (CAP N1) between younger and older adults with and without a self-reported history of noise exposure in a large sample of human participants (63 younger adults 18-30 years of age, 103 older adults 50-86 years of age). CAP N1 response amplitudes were smaller in older than younger adults. Noise exposure history did not appear to predict CAP N1 response amplitudes, nor did the effect of noise exposure history interact with age. We then incorporated our results into two meta-analyses of published studies of age and noise exposure history effects on AN response amplitudes in neurotypical human samples. The meta-analyses found that age effects across studies are robust (r=-0.407), but noise-exposure effects are weak (r=-0.152). We conclude that noise-exposure effects may be highly variable depending on sample characteristics, study design, and statistical approach, and researchers should be cautious when interpreting results. The underlying pathology of age-related and noise-induced changes in AN function are difficult to determine in living humans, creating a need for longitudinal studies of changes in AN function across the lifespan and histological examination of the AN from temporal bones collected post-mortem.

Iron deficiency at birth and risk of hidden hearing loss in infants modification by socioeconomic status: mother-newborn cohort in Shenyang, China.

OBJECTIVE: The diagnosis of hidden hearing loss (HHL) in calm state has not yet been determined, while the nutritional status is not involved in its pathogenic risk factors. In utero iron deficiency (ID) may delay auditory neural maturation in infants. We evaluated the association between ID and HHL as well as the modification effect of socioeconomic status (SES) on this association in newborns. STUDY DESIGN: We included 859 mother-newborns from the baseline of this observational northeast cohort. Data on exposure assessment included iron status [maternal hemoglobin (Hb) and neonatal heel prick serum ferritin (SF)] and SES (occupation, education and income). Auditory neural maturation was reflected by auditory brainstem response (ABR) testing and electrocochleography (ECochG). RESULTS: Iron status and SES were independently and jointly associated with the prediction of neonatal HHL by logistic and linear regression model. The mediation effects were performed by Process. ID increased absolute latency wave V, interpeak latency (IPL) III-V, and summting potentials (SP) /action potentials (AP), which were combined as HHL. Low SES showed the highest risk of HHL and the highest levels of related parameters in ID newborns. Moreover, after Corona Virus Disease 2019 (COVID-19) were positive, preschool children who experience ID in neonatal period were more likely to suffer from otitis media with effusion (OME). High SES also showed similar risk effects. CONCLUSION: Both low and high SES may strengthen the risk of ID on neonatal HHL in Northeast China.

[Mechanism of noise induced hidden hearing loss based on proteomics].

Objective: To explore the mechanism of noise-induced hidden hearing loss by proteomics. Methods: In October 2022, 64 SPF male C57BL/6J mice were divided into control group and noise exposure group with 32 mice in each group according to random sampling method. The noise exposure group was exposed to 100 dB sound pressure level, 2000-16000 Hz broadband noise for 2 h, and the mouse hidden hearing loss model was established. Auditory brainstem response (ABR) was used to test the change of hearing threshold of mice on the 7th day after noise exposure, the damage of basal membrane hair cells was observed by immunofluorescence, and the differentially expressed proteins in the inner ear of mice in each group were identified and analyzed by 4D-Label-free quantitative proteomics, and verified by Western blotting. The results were statistically analyzed by ANOVA and t test. Results: On the 7th day after noise exposure, there was no significant difference in hearing threshold between the control group and the noise exposure group at click and 8000 Hz acoustic stimulation (P>0.05) . The hearing threshold in the noise exposure group was significantly higher than that in the control group under 16000 Hz acoustic stimulation (P<0.05) . Confocal immunofluorescence showed that the basal membrane hair cells of cochlear tissue in noise exposure group were arranged neatly, but the relative expression of C-terminal binding protein 2 antibody of presynaptic membrane in middle gyrus and basal gyrus was significantly lower than that in control group (P<0.05) . GO enrichment analysis showed that the functions of differentially expressed proteins were mainly concentrated in membrane potential regulation, ligand-gated channel activity, and ligand-gated ion channel activity. KEGG pathway enrichment analysis showed that differentially expressed proteins were significantly enriched in phosphatidylinositol 3 kinase-protein kinase B (PI3K-Akt) signaling pathway, NOD-like receptor signaling pathway, calcium signaling pathway, etc. Western blotting showed that the expression of inositol 1, 4, 5-trisphosphate receptor 3 (Itpr3) was increased and the expression of solute carrier family 38 member 2 (Slc38a2) was decreased in the noise exposure group (P<0.05) . Conclusion: Through proteomic analysis, screening and verification of the differential expression proteins Itpr3 and Slc38a2 in the constructed mouse noise-induced hidden hearing loss model, the glutaminergic synaptic related pathways represented by Itpr3 and Slc38a2 may be involved in the occurrence of hidden hearing loss.

The human OPA1delTTAG mutation induces adult onset and progressive auditory neuropathy in mice.

Dominant optic atrophy (DOA) is one of the most prevalent forms of hereditary optic neuropathies and is mainly caused by heterozygous variants in OPA1, encoding a mitochondrial dynamin-related large GTPase. The clinical spectrum of DOA has been extended to a wide variety of syndromic presentations, called DOAplus, including deafness as the main secondary symptom associated to vision impairment. To date, the pathophysiological mechanisms underlying the deafness in DOA remain unknown. To gain insights into the process leading to hearing impairment, we have analyzed the Opa1delTTAG mouse model that recapitulates the DOAplus syndrome through complementary approaches combining morpho-physiology, biochemistry, and cellular and molecular biology. We found that Opa1delTTAG mutation leads an adult-onset progressive auditory neuropathy in mice, as attested by the auditory brainstem response threshold shift over time. However, the mutant mice harbored larger otoacoustic emissions in comparison to wild-type littermates, whereas the endocochlear potential, which is a proxy for the functional state of the stria vascularis, was comparable between both genotypes. Ultrastructural examination of the mutant mice revealed a selective loss of sensory inner hair cells, together with a progressive degeneration of the axons and myelin sheaths of the afferent terminals of the spiral ganglion neurons, supporting an auditory neuropathy spectrum disorder (ANSD). Molecular assessment of cochlea demonstrated a reduction of Opa1 mRNA level by greater than 40%, supporting haploinsufficiency as the disease mechanism. In addition, we evidenced an early increase in Sirtuin 3 level and in Beclin1 activity, and subsequently an age-related mtDNA depletion, increased oxidative stress, mitophagy as well as an impaired autophagic flux. Together, these results support a novel role for OPA1 in the maintenance of inner hair cells and auditory neural structures, addressing new challenges for the exploration and treatment of OPA1-linked ANSD in patients.

Quantifying the Impact of Auditory Deafferentation on Speech Perception.

The past decade has seen a wealth of research dedicated to determining which and how morphological changes in the auditory periphery contribute to people experiencing hearing difficulties in noise despite having clinically normal audiometric thresholds in quiet. Evidence from animal studies suggests that cochlear synaptopathy in the inner ear might lead to auditory nerve deafferentation, resulting in impoverished signal transmission to the brain. Here, we quantify the likely perceptual consequences of auditory deafferentation in humans via a physiologically inspired encoding-decoding model. The encoding stage simulates the processing of an acoustic input stimulus (e.g., speech) at the auditory periphery, while the decoding stage is trained to optimally regenerate the input stimulus from the simulated auditory nerve firing data. This allowed us to quantify the effect of different degrees of auditory deafferentation by measuring the extent to which the decoded signal supported the identification of speech in quiet and in noise. In a series of experiments, speech perception thresholds in quiet and in noise increased (worsened) significantly as a function of the degree of auditory deafferentation for modeled deafferentation greater than 90%. Importantly, this effect was significantly stronger in a noisy than in a quiet background. The encoding-decoding model thus captured the hallmark symptom of degraded speech perception in noise together with normal speech perception in quiet. As such, the model might function as a quantitative guide to evaluating the degree of auditory deafferentation in human listeners.

Utility of Extended High-Frequency Audiograms in Clinical Practice.

OBJECTIVES: Extended high-frequency (EHF) audiometry elicits pure-tone thresholds at frequencies above 8 kHz, which are not included in routine clinical testing. This study explores the utility of EHF audiometry in patients with various audiologic symptoms despite normal-hearing thresholds at ≤8 kHz. METHODS: A retrospective review was performed of all patients receiving conventional (250-8 kHz) and EHF (9-20 kHz) audiometry at a tertiary otological referral center between April 2021 and August 2022. Only patients with audiologic symptoms and pure-tone thresholds ≤25 dB HL at ≤8 kHz bilaterally on routine testing were included in subsequent analysis. EHF-PTA was defined for each ear as an average of the air conduction thresholds at 9.0, 10.0, 11.2, 12.5, 14.0, 16.0, 18.0, and 20.0 kHz. RESULTS: Of the 50 patients who received EHF testing, 40 had audiologic symptoms and normal conventional audiograms at ≤8 kHz. Twenty-five of the 40 (62.5%) were found to have hearing loss in the highest frequencies. Patients with EHF hearing loss (EHF-HL) were more likely to report subjective hearing loss. Age was significantly greater in those with EHF-HL compared with those without EHF-HL, and age was positively correlated with the degree of EHF-HL. CONCLUSION: EHF testing correlates with audiologic symptoms in patients with normal testing at ≤8 kHz and may be considered when standard audiometry is normal. Additional data are warranted to create an evidenced-based, clinical algorithm for EHF audiometry that can guide treatment, direct mitigation strategies, and potentially identify those at higher risk of hearing loss over time. LEVEL OF EVIDENCE: 4 Laryngoscope, 134:907-910, 2024.

Sinaptopatia coclear e perda auditiva oculta: uma revisão de escopo / Cochlear synaptopathy and hidden hearing loss: a scoping review

RESUMO Objetivo Identificar as definições fisiopatológicas adotadas pelos estudos que investigaram a "sinaptopatia coclear" (SC) e "perda auditiva oculta" (PAO). Estratégia de pesquisa Utilizou-se a combinação de unitermos "Auditory Synaptopathy" or "Neuronal Synaptopathy" or "Hidden Hearing Loss" com "etiology" or "causality" or "diagnosis" nas bases de dados EMBASE, Pubmed (MEDLINE), CINAHL (EBSCO) e Web of Science. Critérios de seleção Incluiu-se estudos que investigaram a SC ou PAO em humanos com procedimentos comportamentais e/ou eletrofisiológicos. Análise dos dados Realizou-se a análise e extração de dados quanto a terminologia, definição e população estudada. Resultados Foram incluídos 49 artigos. Destes, 61,2% utilizaram a terminologia SC, 34,7% ambos os termos e 4,1% utilizaram PAO. As condições mais estudadas foram exposição ao ruído e zumbido. Conclusão A terminologia SC foi empregada na maioria dos estudos, com referência ao processo fisiopatológico de desaferenciação entre as fibras do nervo coclear e as células ciliadas internas

ABSTRACT Purpose To identify the pathophysiological definitions adopted by studies investigating "cochlear synaptopathy" (CS) and "hidden hearing loss" (HHL). Research strategies The combination of keywords "Auditory Synaptopathy" or "Neuronal Synaptopathy" or "Hidden Hearing Loss" with "etiology" or "causality" or "diagnosis" was used in the databases EMBASE, Pubmed (MEDLINE), CINAHL (EBSCO), and Web of Science. Selection criteria Studies that investigated CS or HHL in humans using behavioral and/or electrophysiological procedures were included. Data analysis Data analysis and extraction were performed with regard to terminology, definitions, and population. Results 49 articles were included. Of these, 61.2% used the CS terminology, 34.7% used both terms, and 4.1% used HHL. The most-studied conditions were exposure to noise and tinnitus. Conclusion CS terminology was used in most studies, referring to the pathophysiological process of deafferentiation between the cochlear nerve fibers and inner hair cells.

Normal behavioral discrimination of envelope statistics in budgerigars with kainate-induced cochlear synaptopathy.

Cochlear synaptopathy is a common pathology in humans associated with aging and potentially sound overexposure. Synaptopathy is widely expected to cause "hidden hearing loss," including difficulty perceiving speech in noise, but support for this hypothesis is controversial. Here in budgerigars (Melopsittacus undulatus), we evaluated the impact of long-term cochlear synaptopathy on behavioral discrimination of Gaussian noise (GN) and low-noise noise (LNN) signals processed to have a flatter envelope. Stimuli had center frequencies of 1-3kHz, 100-Hz bandwidth, and were presented at sensation levels (SLs) from 10 to 30dB. We reasoned that narrowband, low-SL stimuli of this type should minimize spread of excitation across auditory-nerve fibers, and hence might reveal synaptopathy-related defects if they exist. Cochlear synaptopathy was induced without hair-cell injury using kainic acid (KA). Behavioral threshold tracking experiments characterized the minimum stimulus duration above which animals could reliably discriminate between LNN and GN. Budgerigar thresholds for LNN-GN discrimination ranged from 40 to 60ms at 30dB SL, were similar across frequencies, and increased for lower SLs. Notably, animals with long-term 39-77% estimated synaptopathy performed similarly to controls, requiring on average a ∼7.5% shorter stimulus duration (-0.7±1.0dB; mean difference ±SE) for LNN-GN discrimination. Decision-variable correlation analyses of detailed behavioral response patterns showed that individual animals relied on envelope cues to discriminate LNN and GN, with lesser roles of FM and energy cues; no difference was found between KA-exposed and control groups. These results suggest that long-term cochlear synaptopathy does not impair discrimination of low-level signals with different envelope statistics.

Loss of synaptic ribbons is an early cause in ROS-induced acquired sensorineural hearing loss.

Considerable evidence of reactive oxygen species (ROS) involvement in cochlear hair cell (HC) loss, leading to acquired sensorineural hearing loss (SNHL), were reported. Cochlear synaptopathy between HCs and spiral ganglion neurons has been gathering attention as a cochlear HC loss precursor not detectable by normal auditory evaluation. However, the molecular mechanisms linking ROS with HC loss, as well as the relationship between ROS and cochlear synaptopathy have not been elucidated. Here, we examined these linkages using NOX4-TG mice, which constitutively produce ROS without stimulation. mRNA levels of Piccolo 1, a major component of the synaptic ribbon (a specialized structure surrounded by synaptic vesicles in HCs), were decreased in postnatal day 6 NOX4-TG mice cochleae compared to those in WT mice; they were also decreased by noise exposure in 2-week-old WT cochleae. As noise exposure induces ROS production, this suggests that the synaptic ribbon is a target of ROS. The level of CtBP2, another synaptic ribbon component, was significantly lower in NOX4-TG cochleae of 1-month-old and 4-month-old mice compared to that in WT mice, although no significant differences were noted at 1.5- and 2-months. The decrease in CtBP2 plateaued in 4-month-old NOX4-TG, while it gradually decreased from 1 to 6 months in WT mice. Furthermore, CtBP2 level in 2-month-old NOX4-TG mice decreased significantly after exposure to cisplatin and noise compared to that in WT mice. These findings suggest that ROS lead to developmental delays and early degeneration of synaptic ribbons, which could be potential targets for novel therapeutics for ROS-induced SNHL.

Hidden Hearing Loss, Cochlear Synaptopathy and Occupational Noise / Pérdida Auditiva Oculta, Sinaptopatía Coclear y Ruido Ocupacional

Introducción: La sinaptopatía coclear por exposición a ruido (SCER) es definida como una alteración funcional transitoria o permanente de las sinapsis en cinta de las células pilosas internas de la cóclea. Este artículo tiene el objetivo de comentar la utilidad de la identificación temprana de la pérdida auditiva oculta por SCER basado en marcadores audiológicos y en la metodología usada en grupos clínicos para su búsqueda.Método: Revisión de la literatura relacionada en bases científicas y la narración descriptiva de los resultados.Resultados: La SCER produce una pérdida auditiva oculta en pacientes con audiograma normal, principalmente obreros o individuos expuestos a niveles de ruido intenso. Los principales estudios de identificación de la SCER han sido realizados principalmente en estudiantes universitarios o en músicos.Conclusiones: Son necesarios ajustes en la política de salud auditiva para una amplia identificación temprana de la SCER en las poblaciones en riesgo para la pérdida auditiva oculta y luchar por una regulación del daño. (AU)

Introduction: Cochlear synaptopathy after noise exposure (CSNE) is defined as the transient or permanent func-tional damage to the ribbon synapsis of the inner hair cells of the cochlea. This article has the objective of comment the usefulness of early identification of the hidden hearing loss after CSNE based on audiological markers and in changes in the clinical methodology in clinical groups for its searching.Method: Review of related literature in scientific databases and narrative description of results.Results: CSNE results in a hidden hearing loss in patients with normal pitch audiogram, mainly workers or indi-viduals exposed to high noise levels. The main studies of identification have been performed mainly in groups of students from college or musicians.Conclusions: Is necessary adjustments in hearing health policy for an wide early identification of CSNE in at risk populations for the identification of the hidden hearing loss and fight for its damage regulation. (AU)

Healthcare Professionals and Noise-Generating Tools: Challenging Assumptions about Hearing Loss Risk.

Hearing loss is a significant global health concern, affecting billions of people and leading to various physical, mental, and social consequences. This paper focuses on the risk of noise-induced hearing loss (NIHL) among specific healthcare professionals, especially ear surgeons, orthopaedic surgeons, dentists, and dental hygienists, who frequently use noisy instruments in their professions. While studies on these professionals' noise exposure levels are limited, certain conditions and factors could pose a risk to their hearing. Measures such as engineering and administrative controls, regular audiometric testing, and the use of hearing protection devices are crucial in preventing NIHL. Early detection and intervention are also vital to mitigate further damage. This paper proposes the results of a modified screening protocol, including questionnaires, audiometry, and additional diagnostic tests to identify and address potential hearing disorders. Specific healthcare professionals should remain aware of the risks, prioritize hearing protection, and undergo regular monitoring to safeguard their long-term auditory well-being.

Hidden Hearing Loss, Cochlear Synaptopathy and Occupational Noise / Pérdida Auditiva Oculta, Sinaptopatía Coclear y Ruido Ocupacional

Introducción: La sinaptopatía coclear por exposición a ruido (SCER) es definida como una alteración funcional transitoria o permanente de las sinapsis en cinta de las células pilosas internas de la cóclea. Este artículo tiene el objetivo de comentar la utilidad de la identificación temprana de la pérdida auditiva oculta por SCER basado en marcadores audiológicos y en la metodología usada en grupos clínicos para su búsqueda.Método: Revisión de la literatura relacionada en bases científicas y la narración descriptiva de los resultados.Resultados: La SCER produce una pérdida auditiva oculta en pacientes con audiograma normal, principalmente obreros o individuos expuestos a niveles de ruido intenso. Los principales estudios de identificación de la SCER han sido realizados principalmente en estudiantes universitarios o en músicos.Conclusiones: Son necesarios ajustes en la política de salud auditiva para una amplia identificación temprana de la SCER en las poblaciones en riesgo para la pérdida auditiva oculta y luchar por una regulación del daño (AU)

Introduction: Cochlear synaptopathy after noise exposure (CSNE) is defined as the transient or permanent func-tional damage to the ribbon synapsis of the inner hair cells of the cochlea. This article has the objective of comment the usefulness of early identification of the hidden hearing loss after CSNE based on audiological markers and in changes in the clinical methodology in clinical groups for its searching.Method: Review of related literature in scientific databases and narrative description of results.Results: CSNE results in a hidden hearing loss in patients with normal pitch audiogram, mainly workers or indi-viduals exposed to high noise levels. The main studies of identification have been performed mainly in groups of students from college or musicians.Conclusions: Is necessary adjustments in hearing health policy for an wide early identification of CSNE in at risk populations for the identification of the hidden hearing loss and fight for its damage regulation (AU)

Correlation between pure tone audiometry at all frequencies and distortion product otoacoustic emission of patients with hidden hearing loss.

To explore the correlation between pure tone audiometry at all frequencies and distortion product otoacoustic emission (DPOAE) of hidden hearing loss (HHL). The workers exposed to noise from a factory in Zhangjiakou (noise exposure group, n = 73) and normal young and middle-aged people recruited by society (control group, n = 77) from August 2021 to April 2022 were study subjects, and all of them underwent audiometry in clinic. Compared with the control group, the noise exposure group had significantly higher threshold by extended high-frequency audiometry at all frequencies and higher signal-to-noise ratio threshold (SNR50) (all P < 0.001), and higher amplitude ratio of SP to AP of the waveform induced by short sound at 96, 90, 80 and 70 dB nHL and lower SNR at 6 kHz and above (all P < 0.05). The pure tone audiometry was correlated with DPOAE test results at the frequencies of 6, 8, 9 and 10 kHz (P < 0.001). The results of speech audiometry in noise were related to the average SNR of DPOAE test at each frequency (P = 0.026,r = -0.265). The ratio of SP to AP in electrocochleogram recorded at the intensity of 96 dB nHL was correlated with the average SNR at 6 kHz and above in DPOAE test (P = 0.018,r = -0.461), and with the average auditory threshold at each frequency in extended high-frequency audiometry (P = 0.032, r = 0.421). DPOAE has certain value in detecting HHL.

Middle Ear Muscle Reflex in Normal-Hearing Individuals with Occupational Noise Exposure.

Objectives: Noise-induced cochlear synaptopathy is studied extensively in animal models. The diagnosis of synaptopathy in humans is challenging and the roles of many noninvasive measures in identifying synaptopathy are being explored. The acoustic middle ear muscle reflex (MEMR) can be considered as a vital tool since noise exposure affects the low-spontaneous rate fibers that play an important role in elicitation of MEMR. The present study aimed at measuring MEMR threshold and MEMR strength. Design: The study participants were divided into two groups. All the participants had normal-hearing thresholds. The control group consisted of 25 individuals with no occupational noise exposure whereas noise exposure group had 25 individuals who were exposed to occupational noise of 85 dBA for a minimum period of 1 year. MEMR threshold and strength was assessed for pure tones (500 Hz and 1000 Hz) and broadband noise. Results: The results showed that the MEMR threshold was similar in both the groups. MEMR strength was reduced in noise exposure group compared to control group. Conclusions: The results of the study suggest that MEMR strength could be used as a sensitive measure in identifying cochlear synaptopathy with careful consideration of the stimulus characteristics.

The value of headphone accommodations in Apple Airpods Pro for managing speech-in-noise hearing difficulties of individuals with normal audiograms.

OBJECTIVE: To investigate the extent to which Headphone Accommodations in Apple AirPods Pro attend to the hearing needs of individuals with normal audiograms who experience hearing difficulties in noisy environments. DESIGN: Single-arm interventional study using acoustic measures, speech-in-noise laboratory testing, and real-world measures via questionnaires and ecological momentary assessment. STUDY SAMPLE: Seventeen normal-hearing individuals (9 female, 21-59 years) with self-reported hearing-in-noise difficulties. RESULTS: Acoustic measures showed that, relative to unaided, AirPods Pro provided a SNR advantage of +5.4 dB. Speech intelligibility performance in laboratory testing increased 11.8% with AirPods Pro, relative to unaided. On average, participants trialling AirPods Pro in real-world noisy venues reported that their overall hearing experience was a bit better than without them. Five participants (29%) reported that they would continue using AirPods Pro in the future. The most relevant barriers that would discourage their future use were limited hearing benefit, discomfort, and stigma. CONCLUSIONS: Occasional use of AirPods Pro may help some individuals with normal audiograms ameliorate their speech-in-noise hearing difficulties. The identified barriers may inspire the development of new technological solutions aimed at providing an optimal management strategy for the hearing difficulties of this segment of the population.