From laboratory to clinic: a large scale study of distortion product otoacoustic emissions in ears with normal hearing and ears with hearing loss

The relationship between distortion product otoacoustic emissions and audiometric thresholds in the extended high-frequency range

Distortion product otoacoustic emissions (DPOAEs) and behavioral audiometry are routinely used for hearing screening and assessment. These measures provide related information about hearing status as both are sensitive to cochlear pathologies. However, DPOAE testing is quicker and does not require a behavioral response. Despite these practical advantages, DPOAE testing is often limited to screening only low and mid- frequencies. Variation in ear canal acoustics across ears and probe placements has resulted in less reliable measurements of DPOAEs near 4 kHz and above where standing waves commonly occur. Stimulus calibration in forward pressure level and responses in emitted pressure level can reduce measurement variability. Using these calibrations, this study assessed the correlation between audiometry and DPOAEs in the extended high frequencies where stimulus calibrations and responses are most susceptible to the effect of standing waves. Behavioral thresholds and DPOAE amplitudes were negatively correlated, and DPOAE amplitudes in emitted pressure level accounted for twice as much variance as amplitudes in sound pressure level. Both measures were correlated with age. These data show that with appropriate calibration methods, extended high-frequency DPOAEs are sensitive to differences in audiometric thresholds and highlight the need to consider calibration techniques in clinical and research applications of DPOAEs.

Predictors of Speech-in-Noise Understanding in a Population of Occupationally Noise-Exposed Individuals

Understanding speech in noise is particularly difficult for individuals occupationally exposed to noise due to a mix of noise-induced auditory lesions and the energetic masking of speech signals. For years, the monitoring of conventional audiometric thresholds has been the usual method to check and preserve auditory function. Recently, suprathreshold deficits, notably, difficulties in understanding speech in noise, has pointed out the need for new monitoring tools. The present study aims to identify the most important variables that predict speech in noise understanding in order to suggest a new method of hearing status monitoring. Physiological (distortion products of otoacoustic emissions, electrocochleography) and behavioral (amplitude and frequency modulation detection thresholds, conventional and extended high-frequency audiometric thresholds) variables were collected in a population of individuals presenting a relatively homogeneous occupational noise exposure. Those variables were used as predictors in a statistical model (random forest) to predict the scores of three different speech-in-noise tests and a self-report of speech-in-noise ability. The extended high-frequency threshold appears to be the best predictor and therefore an interesting candidate for a new way of monitoring noise-exposed professionals.

Reliable Long-Term Serial Evaluation of Cochlear Function Using Pulsed Distortion-Product Otoacoustic Emissions: Analyzing Levels and Pressure Time Courses

OBJECTIVES

To date, there is no international standard on how to use distortion-product otoacoustic emissions (DPOAEs) in serial measurements to accurately detect changes in the function of the cochlear amplifier due, for example, to ototoxic therapies, occupational noise, or the development of regenerative therapies. The use of clinically established standard DPOAE protocols for serial monitoring programs appears to be hampered by multiple factors, including probe placement and calibration effects, signal-processing complexities associated with multiple sites of emission generation as well as suboptimal selection of stimulus parameters.

DESIGN

Pulsed DPOAEs were measured seven times within 3 months for f2 = 1 to 14 kHz and L2 = 25 to 80 dB SPL in 20 ears of 10 healthy participants with normal hearing (mean age = 32.1 ± 9.7 years). L1 values were computed from individual optimal-path parameters derived from the corresponding individual DPOAE level map in the first test session. Three different DPOAE metrics for evaluating the functional state of the cochlear amplifier were investigated with respect to their test-retest reliability: (1) the interference-free, nonlinear-distortion component level (LOD), (2) the time course of the DPOAE-envelope levels, LDP(t), and (3) the squared, zero-lag correlation coefficient () between the time courses of the DPOAE-envelope pressures, pDP(t), measured in two sessions. The latter two metrics include the two main DPOAE components and their state of interference.

RESULTS

Collated over all sessions and frequencies, the median absolute difference for LOD was 1.93 dB and for LDP(t) was 2.52 dB; the median of was 0.988. For the low (f2 = 1 to 3 kHz), mid (f2 = 4 to 9 kHz), and high (f2 = 10 to 14 kHz) frequency ranges, the test-retest reliability of LOD increased with increasing signal to noise ratio (SNR).

CONCLUSIONS

On the basis of the knowledge gained from this study on the test-retest reliability of pulsed DPOAE signals and the current literature, we propose a DPOAE protocol for future serial monitoring applications that takes into account the following factors: (1) separation of DPOAE components, (2) use of individually optimal stimulus parameters, (3) SNR of at least 15 dB, (4) accurate pressure calibration, (5) consideration of frequency- and level-dependent test-retest reliabilities and corresponding reference ranges, and (6) stimulus levels L2 that are as low as possible with sufficient SNR to capture the nonlinear functional state of the cochlear amplifier operating at its highest gain.

Deep Learning Models for Predicting Hearing Thresholds Based on Swept-Tone Stimulus-Frequency Otoacoustic Emissions

OBJECTIVES

This study aims to develop deep learning (DL) models for the quantitative prediction of hearing thresholds based on stimulus-frequency otoacoustic emissions (SFOAEs) evoked by swept tones.

DESIGN

A total of 174 ears with normal hearing and 388 ears with sensorineural hearing loss were studied. SFOAEs in the 0.3 to 4.3 kHz frequency range were recorded using linearly swept tones at a rate of 2 Hz/msec, with stimulus level changing from 40 to 60 dB SPL in 10 dB steps. Four DL models were used to predict hearing thresholds at octave frequencies from 0.5 to 4 kHz. The models-a conventional convolutional neural network (CNN), a hybrid CNN-k-nearest neighbor (KNN), a hybrid CNN-support vector machine (SVM), and a hybrid CNN-random forest (RF)-were individually built for each frequency. The input to the DL models was the measured raw SFOAE amplitude spectra and their corresponding signal to noise ratio spectra. All DL models shared a CNN-based feature self-extractor. They differed in that the conventional CNN utilized a fully connected layer to make the final regression decision, whereas the hybrid CNN-KNN, CNN-SVM, and CNN-RF models were designed by replacing the last fully connected layer of CNN model with a traditional machine learning (ML) regressor, that is, KNN, SVM, and RF, respectively. The model performance was evaluated using mean absolute error and SE averaged over 20 repetitions of 5 × 5 fold nested cross-validation. The performance of the proposed DL models was compared with two types of traditional ML models.

RESULTS

The proposed SFOAE-based DL models resulted in an optimal mean absolute error of 5.98, 5.22, 5.51, and 6.06 dB at 0.5, 1, 2, and 4 kHz, respectively, superior to that obtained by the traditional ML models. The produced SEs were 8.55, 7.27, 7.58, and 7.95 dB at 0.5, 1, 2, and 4 kHz, respectively. All the DL models outperformed any of the traditional ML models.

CONCLUSIONS

The proposed swept-tone SFOAE-based DL models were capable of quantitatively predicting hearing thresholds with satisfactory performance. With DL techniques, the underlying relationship between SFOAEs and hearing thresholds at disparate frequencies was explored and captured, potentially improving the diagnostic value of SFOAEs.

Associations Between Physiological Correlates of Cochlear Synaptopathy and Tinnitus in a Veteran Population

PURPOSE

Animal models and human temporal bones indicate that noise exposure is a risk factor for cochlear synaptopathy, a possible etiology of tinnitus. Veterans are exposed to high levels of noise during military service. Therefore, synaptopathy may explain the high rates of noise-induced tinnitus among Veterans. Although synaptopathy cannot be directly evaluated in living humans, animal models indicate that several physiological measures are sensitive to synapse loss, including the auditory brainstem response (ABR), the middle ear muscle reflex (MEMR), and the envelope following response (EFR). The purpose of this study was to determine whether tinnitus is associated with reductions in physiological correlates of synaptopathy that parallel animal studies.

METHOD

Participants with normal audiograms were grouped according to Veteran status and tinnitus report (Veterans with tinnitus, Veterans without tinnitus, and non-Veteran controls). The effects of being a Veteran with tinnitus on ABR, MEMR, and EFR measurements were independently modeled using Bayesian regression analysis.

RESULTS

Modeled point estimates of MEMR and EFR magnitude showed reductions for Veterans with tinnitus compared with non-Veterans, with the most evident reduction observed for the EFR. Two different approaches were used to provide context for the Veteran tinnitus effect on the EFR by comparing to age-related reductions in EFR magnitude and synapse numbers observed in previous studies. These analyses suggested that EFR magnitude/synapse counts were reduced in Veterans with tinnitus by roughly the same amount as over 20 years of aging.

CONCLUSION

These findings suggest that cochlear synaptopathy may contribute to tinnitus perception in noise-exposed Veterans.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.24347761.

Telemedicine Referral to Improve Access to Specialty Care for Preschool Children in Rural Alaska: A Cluster-Randomized Controlled Trial

OBJECTIVES

Preschool programs provide essential preventive services, such as hearing screening, but in rural regions, limited access to specialists and loss to follow-up compound rural health disparities. We conducted a parallel-arm cluster-randomized controlled trial to evaluate telemedicine specialty referral for preschool hearing screening. The goal of this trial was to improve timely identification and treatment of early childhood infection-related hearing loss, a preventable condition with lifelong implications. We hypothesized that telemedicine specialty referral would improve time to follow-up and the number of children receiving follow-up compared with the standard primary care referral.

DESIGN

We conducted a cluster-randomized controlled trial in K-12 schools in 15 communities over two academic years. Community randomization occurred within four strata using location and school size. In the second academic year (2018-2019), an ancillary trial was performed in the 14 communities that had preschools to compare telemedicine specialty referral (intervention) to standard primary care referral (comparison) for preschool hearing screening. Randomization of communities from the main trial was used for this ancillary trial. All children enrolled in preschool were eligible. Masking was not possible because of timing in the second year of the main trial, but referral assignment was not openly disclosed. Study team members and school staff were masked throughout data collection, and statisticians were blinded to allocation during analysis. Preschool screening occurred once, and children who were referred for possible hearing loss or ear disease were monitored for follow-up for 9 months from the screening date. The primary outcome was time to ear/hearing-related follow-up from the date of screening. The secondary outcome was any ear/hearing follow-up from screening to 9 months. Analyses were conducted using an intention-to-treat approach.

RESULTS

A total of 153 children were screened between September 2018 and March 2019. Of the 14 communities, 8 were assigned to the telemedicine specialty referral pathway (90 children), and 6 to the standard primary care referral pathway (63 children). Seventy-one children (46.4%) were referred for follow-up: 39 (43.3%) in the telemedicine specialty referral communities and 32 (50.8%) in the standard primary care referral communities. Of children referred, 30 (76.9%) children in telemedicine specialty referral communities and 16 (50.0%) children in standard primary care referral communities received follow-up within 9 months (Risk Ratio = 1.57; 95% confidence interval [CI], 1.22 to 2.01). Among children who received follow-up, median time to follow-up was 28 days (interquartile range [IQR]: 15 to 71) in telemedicine specialty referral communities compared with 85 days (IQR: 26 to 129) in standard primary care referral communities. Mean time to follow-up for all referred children was 4.5 (event time ratio = 4.5; 95% CI, 1.8 to 11.4; p = 0.045) times faster in telemedicine specialty referral communities compared with standard primary care referral communities in the 9-month follow-up time frame.

CONCLUSIONS

Telemedicine specialty referral significantly improved follow-up and reduced time to follow-up after preschool hearing screening in rural Alaska. Telemedicine referrals could extend to other preventive school-based services to improve access to specialty care for rural preschool children.

Characterizing a Joint Reflection-Distortion OAE Profile in Humans With Endolymphatic Hydrops

OBJECTIVES

Endolymphatic hydrops (EH), a hallmark of Meniere disease, is an inner-ear disorder where the membranes bounding the scala media are distended outward due to an abnormally increased volume of endolymph. In this study, we characterize the joint-otoacoustic emission (OAE) profile, a results profile including both distortion- and reflection-class emissions from the same ear, in individuals with EH and speculate on its potential utility in clinical assessment and monitoring.

DESIGN

Subjects were 16 adults with diagnosed EH and 18 adults with normal hearing (N) matched for age. Both the cubic distortion product (DP) OAE, a distortion-type emission, and the stimulus-frequency (SF) OAE, a reflection-type emission, were measured and analyzed as a joint OAE profile. OAE level, level growth (input/output functions), and phase-gradient delays were measured at frequencies corresponding to the apical half of the human cochlea and compared between groups.

RESULTS

Normal hearers and individuals with EH shared some common OAE patterns, such as the reflection emissions being generally higher in level than distortion emissions and showing more linear growth than the more strongly compressed distortion emissions. However, significant differences were noted between the EH and N groups as well. OAE source strength (a metric based on OAE amplitude re: stimulus level) was significantly reduced, as was OAE level, at low frequencies in the EH group. These reductions were more marked for distortion than reflection emissions. Furthermore, two significant changes in the configuration of OAE input/output functions were observed in ears with EH: a steepened growth slope for reflection emissions and an elevated compression knee for distortion emissions. SFOAE phase-gradient delays at 40 dB forward-pressure level were slightly shorter in the group with EH compared with the normal group.

CONCLUSIONS

The underlying pathology associated with EH impacts the generation of both emission types, reflection and distortion, as shown by significant group differences in OAE level, growth, and delay. However, hydrops impacts reflection and distortion emissions differently. Most notably, DPOAEs were more reduced by EH than were SFOAEs, suggesting that pathologies associated with the hydropic state do not act identically on the generation of nonlinear distortion at the hair bundle and intracochlear reflection emissions near the peak of the traveling wave. This differential effect underscores the value of applying a joint OAE approach to access both intracochlear generation processes concurrently.

The effect of cumulative noise exposure on distortion product otoacoustic emissions

OBJECTIVE

This study aimed to identify the characteristics of distortion product otoacoustic emissions (DPOAEs) that can be used to differentiate noise-induced hearing loss (NIHL) from age-related hearing loss. A potential index to detect NIHL was defined in terms of its susceptibility to cumulative noise exposure but not to age.

DESIGN

In this cross-sectional cohort study, a job-exposure matrix was used to calculate the cumulative noise exposure. Multivariate linear regression models were used to examine how age and cumulative noise exposure associated with DPOAEs at individual frequencies after adjusting for hypertension, dyslipidaemia, tobacco use and alcohol consumption.

STUDY SAMPLE

The pure-tone audiometry and DPOAEs data collected from 239 male workers in a steel factory.

RESULTS

DPOAEs and DPOAE signal-to-noise ratios (SNRs) at all frequencies were found to be correlated with age, and those at 2, 3, 4 and 6 kHz were correlated with both age and noise exposure. The difference between DPOAE SNR at 1 and 3 kHz showed significant correlation with noise exposure but not with age.

CONCLUSIONS

The results showed that this DPOAE index, the DPOAE SNR at 1 kHz minus the DPOAE SNR at 3 kHz, could add values to audiometric evaluation of NIHL.

Model-based prediction of otoacoustic emission level, noise level, and signal-to-noise ratio during time-synchronous averaging

Although averaging is effective in reducing noise, its efficiency rapidly decreases beyond several hundred averages. Depending on environmental and patient noise levels, several hundred averages may be insufficient for informed clinical decision making. The predictable nature of the otoacoustic emission (OAE) and noise during time-synchronous averaging implicates the use of predictive modeling as an alternative to increased averaging when noise is high. Click-evoked OAEs were measured in 98, normal-hearing subjects. Average OAE and noise levels were calculated for subsets of the total number of averages and then fit using variants of a power function. The accuracy of the models was quantified as the difference between the measured value and model output. Models were used to predict the OAE signal-to-noise ratio (SNR) for a criterion noise level. Based on predictions, the OAE was categorized as present or absent. Model-based decisions were compared to decisions from direct measurements. Model accuracy improved as the number of averages (and SNR in the case of OAEs) from which the model was derived increased. Model-based classifications permitted correct categorization of the OAE status from fewer averages than measurement-based classifications. Furthermore, model-based predictions resulted in fewer false positives (i.e., absent OAE despite normal hearing).

Influence of tinnitus, lifetime noise exposure, and firearm use on hearing thresholds, distortion product otoacoustic emissions, and their relative metric

Distortion product otoacoustic emissions (DPOAEs) and hearing thresholds (HTs) are widely used to evaluate auditory physiology. DPOAEs are sensitive to cochlear amplification processes, while HTs are additionally dependent upon inner hair cells, synaptic junctions, and the auditory nervous system. These distinctions between DPOAEs and HTs might help differentially diagnose auditory dysfunctions. This study aims to differentially diagnose auditory dysfunctions underlying tinnitus, firearm use, and high lifetime noise exposure (LNE) using HTs, DPOAEs, and a derived metric comparing HTs and DPOAEs, in a sample containing overlapping subgroups of 133 normal-hearing young adults (56 with chronic tinnitus). A structured interview was used to evaluate LNE and firearm use. Linear regression was used to model the relationship between HTs and DPOAEs, and their regression residuals were used to quantify their relative agreement. Participants with chronic tinnitus showed significantly elevated HTs, yet DPOAEs remained comparable to those without tinnitus. In contrast, firearm users revealed elevated HTs and significantly lower DPOAEs than predicted from HTs. High LNE was associated with elevated HTs and a proportional decline in DPOAEs, as predicted from HTs. We present a theoretical model to interpret the findings, which suggest neural (or synaptic) dysfunction underlying tinnitus and disproportional mechanical dysfunction underlying firearm use.

Evaluation of Subtle Auditory Impairments with Multiple Audiological Assessments in Normal Hearing Workers Exposed to Occupational Noise

Recent studies involving guinea pigs have shown that noise can damage the synapses between the inner hair cells and spiral ganglion neurons, even with normal hearing thresholds-which makes it important to investigate this kind of impairment in humans. The aim was to investigate, with multiple audiological assessments, the auditory function of normal hearing workers exposed to occupational noise. Altogether, 60 workers were assessed (30 in the noise-exposure group [NEG], who were exposed to occupational noise, and 30 in the control group [CG], who were not exposed to occupational noise); the workers were matched according to age. The following procedures were used: complete audiological assessment; speech recognition threshold in noise (SRTN); speech in noise (SN) in an acoustic field; gaps-in-noise (GIN); transient evoked otoacoustic emissions (TEOAE) and inhibitory effect of the efferent auditory pathway; auditory brainstem response (ABR); and long-latency auditory evoked potentials (LLAEP). No significant difference was found between the groups in SRTN. In SN, the NEG performed worse than the CG in signal-to-noise ratio (SNR) 0 (p-value 0.023). In GIN, the NEG had a significantly lower percentage of correct answers (p-value 0.042). In TEOAE, the NEG had smaller amplitude values bilaterally (RE p-value 0.048; LE p-value 0.045) and a smaller inhibitory effect of the efferent pathway (p-value 0.009). In ABR, the NEG had greater latencies of wave V (p-value 0.017) and interpeak intervals III-V and I-V in the LE (respective p-values: 0.005 and 0.04). In LLAEP, the NEG had a smaller P3 amplitude bilaterally (RE p-value 0.001; LE p-value 0.002). The NEG performed worse than the CG in most of the assessments, suggesting that the auditory function in individuals exposed to occupational noise is impaired, even with normal audiometric thresholds.

A Survey of U.S. Audiologists' Usage of and Attitudes Toward Otoacoustic Emissions

PURPOSE

Otoacoustic emissions (OAEs) provide information on outer hair cell function and have multiple clinical applications. Two types of OAEs, transient-evoked OAEs (TEOAEs) and distortion product OAEs (DPOAEs), are currently utilized in clinical practice. However, it remains unknown how confident U.S. clinicians are in performing and interpreting TEOAEs and DPOAEs. Additionally, the extent to which U.S. audiologists incorporate OAEs for different clinical applications and populations has not been thoroughly investigated. To fill these gaps in knowledge, this study characterized the attitudes toward and usage of TEOAEs and DPOAEs in a sample of U.S. audiologists.

METHOD

This study utilized an online survey distributed to U.S. audiologists through multiple channels from January to March 2021. A total of 214 completed surveys were included in the analysis. Results were analyzed descriptively. Associations between variables and comparisons between users of DPOAEs only and users of TEOAEs and DPOAEs were also examined.

RESULTS

DPOAEs were reportedly utilized more frequently and with greater confidence than TEOAEs. The most common clinical application of both OAE types was a cross-check. Significant associations were found between responses to DPOAE questions and the clinician's setting and patient age. There were some significant differences between users of DPOAEs only and users of TEOAEs and DPOAEs.

CONCLUSIONS

Results suggest that U.S. audiologists utilize OAEs for multiple clinical purposes and that there are appreciable differences in terms of attitudes toward and usage of DPOAEs versus TEOAEs. Future work could investigate the reasons that underlie these differences to further improve clinical implementation of OAEs.

The Effect of Stimuli Level on Distortion Product Otoacoustic Emission in Normal Hearing Adults

The goal of this study is to compare three of the most commonly used primary-level relation paradigms (i.e., Scissors, Boys Town 'Optimal', and Equal-Level) in generation of distortion product otoacoustic emissions (DPOAEs) in normal hearing adults. The generator and reflection components were extracted from DPOAEs in each paradigm. The generator and reflection component levels and input/output (I/O) functions were compared across paradigms and primary-tone levels. The results showed a different I/O function growth behavior across frequency and levels among paradigms. The Optimal paradigm showed a systematic change in the generator and reflection component levels and I/O slopes across primary levels among subjects. Moreover, the levels and slopes in the Optimal paradigm were more distinct across levels with less variations across frequency leading to a systematic change in the DPOAE fine structure across levels. The I/O functions were found to be more sensitive to the selected paradigm; especially the I/O function for the reflection component. The I/O functions of the reflection components showed large variability across frequencies due to different frequency shifts in their microstructure depending on the paradigm. The findings of this study suggested the Optimal paradigm as the proper primary-level relation to study cochlear amplification/compression. The findings of this study shows that care needs to be taken in comparing the findings of different studies that generated DPOAEs with a different level-relation paradigm.

Environmental Factors for Hearing Loss and Middle Ear Disease in Alaska Native Children and Adolescents: A Cross-Sectional Analysis from a Cluster Randomized Trial

OBJECTIVES

Infection-related childhood hearing loss is one of the few preventable chronic health conditions that can affect a child's lifelong trajectory. This study sought to quantify relationships between infection-mediated hearing loss and middle ear disease and environmental factors, such as exposure to wood smoke, cigarette smoke, household crowding, and lack of access to plumbed (running) water, in a northwest region of rural Alaska.

DESIGN

This study is a cross-sectional analysis to estimate environmental factors of infection-related hearing loss in children aged 3 to 21 years. School hearing screenings were performed as part of two cluster randomized trials in rural Alaska over two academic years (2017-2018 and 2018-2019). The first available screening for each child was used for this analysis. Sociodemographic questionnaires were completed by parents/guardians upon entry into the study. Multivariable regression was performed to estimate prevalence differences and prevalence ratios (PR). A priori knowledge about the prevalence of middle ear disease and the difficulty inherent in obtaining objective hearing loss data in younger children led to analysis of children by age (3 to 6 years versus 7 years and older) and a separate multiple imputation sensitivity analysis for pure-tone average (PTA)-based infection-related hearing loss measures.

RESULTS

A total of 1634 children participated. Hearing loss was present in 11.1% of children sampled based on otoacoustic emission as the primary indicator of hearing loss and was not associated with exposure to cigarette smoke (PR = 1.07; 95% confidence interval [CI], 0.48 to 2.38), use of a wood-burning stove (PR = 0.85; 95% CI, 0.55 to 1.32), number of persons living in the household (PR = 1.06; 95% CI, 0.97 to 1.16), or lack of access to running water (PR = 1.38; 95% CI, 0.80 to 2.39). Using PTA as a secondary indicator of hearing loss also showed no association with environmental factors. Middle ear disease was present in 17.4% of children. There was a higher prevalence of middle ear disease in homes without running water versus those with access to running water (PR = 1.53; 95% CI, 1.03 to 2.27). There was little evidence to support any cumulative effects of environmental factors. Heterogeneity of effect models by age found sample prevalence of hearing loss higher for children aged 3 to 6 years (12.2%; 95% CI, 9.3 to 15.7) compared to children 7 years and older (10.6%; 95% CI, 8.9 to 2.6), as well as for sample prevalence of middle ear disease (22.7%; 95% CI, 18.9 to 26.9 and 15.3%; 95% CI, 13.3 to 17.5, respectively).

CONCLUSIONS

Lack of access to running water in the home was associated with increased prevalence of middle ear disease in this rural, Alaska Native population, particularly among younger children (aged 3 to 6 years). There was little evidence in this study that cigarette smoke, wood-burning stoves, and greater numbers of persons in the household were associated with infection-mediated hearing loss or middle ear disease. Future research with larger sample sizes and more sensitive measures of environmental exposure is necessary to further evaluate these relationships. Children who live in homes without access to running water may benefit from earlier and more frequent hearing health visits.

Development of an audiological assessment and diagnostic model for high occupational noise exposure

PURPOSE

To explore the diagnostic auditory indicators of high noise exposure and combine them into a diagnostic model of high noise exposure and possible development of hidden hearing loss (HHL).

METHODS

We recruited 101 young adult subjects and divided them according to noise exposure history into high-risk and low-risk groups. All subjects completed demographic characteristic collection (including age, noise exposure, self-reported hearing status, and headset use) and related hearing examination.

RESULTS

The 8 kHz (P = 0.039) and 10 kHz (P = 0.005) distortion product otoacoustic emission amplitudes (DPOAE) (DPs) in the high-risk group were lower than those in the low-risk group. The amplitudes of the summating potential (SP) (P = 0.017) and action potential (AP) (P = 0.012) of the electrocochleography (ECochG) in the high-risk group were smaller than those in the low-risk group. The auditory brainstem response (ABR) wave III amplitude in the high-risk group was higher than that in the low-risk group. When SNR = - 7.5 dB (P = 0.030) and - 5 dB (P = 0.000), the high-risk group had a lower speech discrimination score than that of the low-risk group. The 10 kHz DPOAE DP, ABR wave III amplitude and speech discrimination score under noise with SNR = - 5 dB were combined to construct a combination diagnostic indicator. The area under the ROC curve was 0.804 (95% CI 0.713-0.876), the sensitivity was 80.39%, and the specificity was 68.00%.

CONCLUSIONS

We expect that high noise exposure can be detected early with this combined diagnostic indicator to prevent HHL or sensorineural hearing loss (SNHL).

TRIAL REGISTRATION NUMBER/DATE OF REGISTRATION

ChiCTR2200057989, 2022/3/25.

Contralateral inhibition of distortion product otoacoustic emissions in young noise-exposed Veterans

Although animal models show a clear link between noise exposure and damage to afferent cochlear synapses, the relationship between noise exposure and efferent function appears to be more complex. Animal studies indicate that high intensity noise exposure reduces efferent medial olivocochlear (MOC) reflex strength, whereas chronic moderate noise exposure is associated with a conditioning effect that enhances the MOC reflex. The MOC reflex is predicted to improve speech-in-noise perception and protects against noise-induced auditory damage by reducing cochlear gain. In humans, MOC reflex strength can be estimated by measuring contralateral inhibition of distortion product otoacoustic emissions (DPOAEs). The objective of this study was to determine the impact of military noise exposure on efferent auditory function by measuring DPOAE contralateral inhibition in young Veterans and non-Veterans with normal audiograms. Compared with non-Veteran controls, Veterans with high levels of reported noise exposure demonstrated a trend of reduced contralateral inhibition across a broad frequency range, suggesting efferent damage. Veterans with moderate noise exposure showed trends of reduced inhibition from 3 to 4 kHz but greater inhibition from 1 to 1.5 kHz, consistent with conditioning. These findings suggest that, in humans, the impact of noise exposure on the MOC reflex differs depending on the noise intensity and duration.

Relative changes in the cochlear summating potentials to paired-clicks predict speech-in-noise perception and subjective hearing acuity

Objective assays of human cochlear synaptopathy (CS) have been challenging to develop. It is suspected that relative summating potential (SP) changes are different in listeners with CS. In this proof-of-concept study, young, normal-hearing adults were recruited and assigned to a low/high-risk group for having CS based on their extended audiograms (9-16 kHz). SPs to paired-clicks with varying inter-click intervals isolated non-refractory receptor components of cochlear activity. Abrupt increases in SPs to paired- vs single-clicks were observed in high-risk listeners. Critically, exaggerated SPs predicted speech-in-noise and subjective hearing abilities, suggesting relative SP changes to rapid clicks might help identify putative synaptopathic listeners.

Characterizing the Relationship Between Reflection and Distortion Otoacoustic Emissions in Normal-Hearing Adults

Otoacoustic emissions (OAEs) arise from one (or a combination) of two basic generation mechanisms in the cochlea: nonlinear distortion and linear reflection. As a result of having distinct generation processes, these two classes of emissions may provide non-redundant information about hair-cell integrity and show distinct sensitivities to cochlear pathology. Here, we characterize the relationship between reflection and distortion emissions in normal hearers across a broad frequency and stimulus-level space using novel analysis techniques. Furthermore, we illustrate the promise of this approach in a small group of individuals with mild-moderate hearing loss. A "joint-OAE profile" was created by measuring interleaved swept-tone stimulus-frequency OAEs (SFOAEs) and 2f1-f2 distortion-product OAEs (DPOAEs) in the same ears using well-considered parameters. OAE spectra and input/output functions were calculated across five octaves. Using our specific recording protocol and analysis scheme, SFOAEs in normal hearers had higher levels than did DPOAEs, with the most pronounced differences occurring at the highest stimulus levels. Also, SFOAE compression occurred at higher stimulus levels (than did DPOAE compression) and its growth in the compressed region was steeper. The diagnostic implications of these findings and the influence of the measurement protocol on both OAEs (and on their relationship) are discussed.

A Smartphone Application and Education Program for Hearing Health Promotion in High School Teenagers

OBJECTIVES

To assess knowledge retention after video-based hearing health education and measure headphone listening behavior change using a novel smartphone application.

METHODS

In this prospective longitudinal study, students participated in video-based hearing health education and hearing screening sessions. Hearing health knowledge was assessed in students and parents after 6 weeks. A novel smartphone application was created to measure daily noise exposure based on volume settings with headphone use and to display the National Institute for Occupational Safety and Health (NIOSH) noise doses with alerts for cumulative daily doses nearing the maximum.

RESULTS

Seventy-six teenage students and parents participated. Eighty three percent of participants identified as a racial or ethnic minority and 66% were of low-income socioeconomic status. Hearing health knowledge was retained in students 6 weeks after education and parents' knowledge improved from baseline. The smartphone app was installed on 12 student phones, and 25% of days monitored exhibited noise doses that exceeded the NIOSH maximum. App use for at least 10 days by nine students showed a significant reduction in average daily noise dose and time spent at the highest volume settings during the second-half of app use.

CONCLUSIONS

Video-based hearing health education with knowledge question reinforcement was associated with knowledge retention in students and improved parental attitudes and knowledge about hearing conservation. A smartphone app with a real-time display of headphone cumulative noise exposure dose identified at-risk students. The integration of hearing health education, hearing screening, and digital health tools has promised to promote positive behavior changes for long-term hearing conservation.

LEVEL OF EVIDENCE

4 Laryngoscope, 2022.

Optimizing distortion product otoacoustic emission recordings in normal-hearing ears by adopting cochlear place-specific stimuli

Distortion product otoacoustic emissions (DPOAEs) provide a window into active cochlear processes and have become a popular clinical and research tool. DPOAEs are commonly recorded using stimulus with fixed presentation levels and frequency ratio irrespective of the test frequency. However, this is inconsistent with the changing mechanical properties of the cochlear partition from the base to the apex that lend specific frequency-dependent spatial properties to the cochlear traveling wave. Therefore, the frequency and level characteristics between the stimulus tones should also need to be adjusted as a function of frequency to maintain optimal interaction between them. The goal of this investigation was to establish a frequency-specific measurement protocol guided by local cochlear mechanics. A broad stimulus parameter space extending up to 20 kHz was explored in a group of normal-hearing individuals. The stimulus frequency ratio yielding the largest 2f₁-f₂ DPOAE level changed as a function of frequency and stimulus level. Specifically, for a constant stimulus level, the frequency ratio producing the largest DPOAE level decreased with increasing frequency. Similarly, at a given f₂ frequency, the stimulus frequency ratio producing the largest DPOAE level became wider as stimulus level increased. These results confirm and strengthen our current understanding of DPOAE generation in the normally functioning cochlea and expand our understanding to previously unexamined higher frequencies. These data support the use of frequency- and level-specific stimulus frequency ratios to maximize DPOAE generation.

Joint Profile Characteristics of Long-Latency Transient Evoked and Distortion Otoacoustic Emissions

PURPOSE

In clinical practice, otoacoustic emissions (OAEs) are interpreted as either "present" or "absent." However, OAEs have the potential to inform about etiology and severity of hearing loss if analyzed in other dimensions. A proposed method uses the nonlinear component of the distortion product OAEs together with stimulus frequency OAEs to construct a joint reflection-distortion profile. The objective of the current study is to determine if joint reflection-distortion profiles can be created using long-latency (LL) components of transient evoked OAEs (TEOAEs) as the reflection-type emission.

METHOD

LL TEOAEs and the nonlinear distortion OAEs were measured from adult ears. Individual input-output (I/O) functions were created, and OAE level was normalized by dividing by the stimulus level yielding individual gain functions. Peak strength, compression threshold, and OAE level at compression threshold were derived from individual gain functions to create joint reflection-distortion profiles.

RESULTS

TEOAEs with a poststimulus window starting at 6 ms had I/O functions with compression characteristics similar to LL TEOAE components. The model fit the LL gain functions, which had R ² > .93, significantly better than the nonlinear distortion OAE gain functions, which had R ² = .596-.99. Interquartile ranges for joint reflection-distortion profiles were larger for compression threshold and OAE level at compression threshold but smaller for peak strength than those previously published.

CONCLUSIONS

The gain function fits LL TEOAEs well. Joint reflection-distortion profiles are a promising method that could enhance diagnosis of hearing loss, and use of the LL TEOAE in the profile for peak strength may be important because of narrow interquartile ranges.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.20323593.

The Impacts of Noise Exposure on the Middle Ear Muscle Reflex in a Veteran Population

PURPOSE

Human studies of noise-induced cochlear synaptopathy using physiological indicators identified in animal models (auditory brainstem response [ABR] Wave I amplitude, envelope following response [EFR], and middle ear muscle reflex [MEMR]) have yielded mixed findings. Differences in the population studied may have contributed to the differing results. For example, due to differences in the intensity level of the noise exposure, noise-induced synaptopathy may be easier to detect in a military Veteran population than in populations with recreational noise exposure. We previously demonstrated a reduction in ABR Wave I amplitude and EFR magnitude for young Veterans with normal audiograms reporting high levels of noise exposure compared to non-Veteran controls. In this article, we expand on the previous analysis in the same population to determine if MEMR magnitude is similarly reduced.

METHOD

Contralateral MEMR growth functions were obtained in 92 young Veterans and non-Veterans with normal audiograms, and the relationship between noise exposure history and MEMR magnitude was assessed. Associations between MEMR magnitude and distortion product otoacoustic emission, EFR, and ABR measurements collected in the same sample were also evaluated.

RESULTS

The results of the statistical analysis, although not conventionally statistically significant, suggest a reduction in mean MEMR magnitude for Veterans reporting high noise exposure compared with non-Veteran controls. In addition, the MEMR appears relatively insensitive to subclinical outer hair cell dysfunction, as measured by distortion product otoacoustic emissions, and is not well correlated with ABR and EFR measurements.

CONCLUSIONS

When combined with our previous ABR and EFR findings in the same population, these results suggest that noise-induced synaptopathy occurs in humans. In addition, the findings indicate that the MEMR may be a good candidate for noninvasive diagnosis of cochlear synaptopathy/deafferentation and that the MEMR may reflect the integrity of different neural populations than the ABR and EFR.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.18665645.

High-Frequency Cochlear Amplifier Dysfunction: A Dominating Contribution to the Cognitive-Ear Link

Objective: The objective of this study was to investigate the role of the high-frequency cochlear dysfunction in the cognitive-ear link.

Methods: Seventy-four presbycusis patients (PC group) and seventy-one age-, sex-, and education-level matched normal hearing controls (NH group) were recruited in this study. Participants underwent a battery of cognitive tests estimated by Montreal Cognitive Assessment (MoCA), Stroop Color-Word Interference Test (Stroop), Symbol Digit Modalities Test (SDMT), Auditory Verbal Learning Test (AVLT), and Trail-Making Test (TMT-A and B), as well as auditory tests including distortion product otoacoustic emission (DPOAE), pure tone (PT) thresholds, and speech reception thresholds (SRT). Data were analyzed using the factor analysis, partial correlation analysis, multiple linear regression models, and mediation models.

Results: Distortion product otoacoustic emission detection amplitudes and PT thresholds performed worse gradually from low to high frequencies in both the NH and PC groups. High-frequency DPOAE (H-DPOAE) was significantly correlated with cognitive domains in the PC group (AVLT: r = 0.30, p = 0.04; SDMT: r = 0.36, p = 0.01; Stroop: r = –0.32, p = 0.03; TMT-A: r = –0.40, p = 0.005; TMT-B: r = –0.34, p = 0.02). Multiple linear regression models showed that H-DPOAE predicted cognitive impairment effectively for aspects of memory (R2 = 0.27, 95% CI, 0.03 to 1.55), attention (R2 = 0.32, 95% CI, –6.18 to –0.40), processing speed (R2 = 0.37, 95% CI, 0.20 to 1.64), and executive function (TMT-A: R2 = 0.34, 95% CI, –5.52 to 1.03; TMT-B: R2 = 0.29, 95% CI, –11.30 to –1.12). H-DPOAE directly affected cognition and fully mediated the relationship between pure tone average (PTA)/SRT and cognitive test scores, excluding MoCA.

Conclusion: This study has demonstrated that the high-frequency cochlear amplifier dysfunction has a direct predictive effect on the cognitive decline and makes a large contribution to the cognitive-ear link.

Short- and mid-term multidisciplinary outcomes of newborns exposed to SARS-CoV-2 in utero or during the perinatal period: preliminary findings

The long-term outcomes of newborns exposed to SARS-CoV-2 infection in utero or during the first hours of life are still unknown. We performed a single-center, prospective, observational study of newborns born from mothers with microbiologically confirmed SARS-CoV-2 infection in pregnancy or at time of delivery. Infants were offered a multidisciplinary follow-up consisting of nasopharyngeal Polymerase Chain Reaction test at birth and at 48-72 h of life, auxological growth and neurological development, serologic testing, and audiological and ophthalmological assessments. One-hundred ninety-eight mothers and 199 newborns were enrolled. Of the 199 newborns, 171 underwent nasopharyngeal swab, four (2.3%) and two (1.15%) children tested positive at birth and 48-72 h of life, respectively. None had SARS-CoV-2 related symptoms. Auxologic and neurologic development were normal in all children during follow-up. Nine out of 59 infants had SARS-CoV-2 IgG at 3 months of life, which was associated with a positive nasopharyngeal swab at birth (P = 0.04). Twenty seven out of 143 (18.8%) newborns had pathologic transitory evoked otoacoustic emissions at birth, although 14/27 repeated after 1 month were normal. Audiological evaluation was completed with Auditory Brainstem Response between the third and sixth month of life in 34 children, showing in all normal hearing threshold. The ophthalmological evaluation found retinal vascular anomalies in 3/20 (15%) children, immature visual acuity in 5/20 (25%) children, and reduced distance attention in 6/20 cases (30%).

CONCLUSIONS

Our study showed that the neonatal and mid-term multidisciplinary outcomes of newborns exposed to SARS-CoV-2 infection in utero or during the first hours of life are mostly positive, with the exception of ophthalmologic findings which, in a preliminary cohort, were abnormal in about 15% of cases. Further prospective, longitudinal studies are needed to better understand the clinical outcomes of children exposed to SARS-CoV-2 in utero and in the early postnatal life.

WHAT IS KNOWN

• In utero mother-to-child transmission of SARS-CoV-2 has been documented by several independent studies. • Neonatal COVID-19 is a systemic disease that can be severe, although rarely.

WHAT IS NEW

• Newborns exposed in utero to SARS-CoV-2 have mostly a normal auxological, audiological, and neurological development during the first months of life. • Fundus fluorescein angiography revealed that up to 5% of newborns exposed in utero to SARS-CoV2 can show retinal and choroidal abnormalities, including peripheral hypofluorescence of the choroid and increased vascular tortuosity.

Envelope following response measurements in young veterans are consistent with noise-induced cochlear synaptopathy

Animal studies have demonstrated that noise exposure can lead to the loss of the synapses between the inner hair cells and their afferent auditory nerve fiber targets without impacting auditory thresholds. Although several non-invasive physiological measures appear to be sensitive to cochlear synaptopathy in animal models, including auditory brainstem response (ABR) wave I amplitude, the envelope following response (EFR), and the middle ear muscle reflex (MEMR), human studies of these measures in samples that are expected to vary in terms of the degree of noise-induced synaptopathy have resulted in mixed findings. One possible explanation for the differing results is that synaptopathy risk is lower for recreational noise exposure than for occupational or military noise exposure. The goal of this analysis was to determine if EFR magnitude and ABR wave I amplitude are reduced among young Veterans with a history of military noise exposure compared with non-Veteran controls with minimal noise exposure. EFRs and ABRs were obtained in a sample of young (19-35 years) Veterans and non-Veterans with normal audiograms and robust distortion product otoacoustic emissions (DPOAEs). The statistical analysis is consistent with a reduction in mean EFR magnitude and ABR wave I amplitude (at 90 dB peSPL) for Veterans with a significant history of noise exposure compared with non-Veteran controls. These findings are in agreement with previous ABR wave I amplitude findings in young Veterans and are consistent with animal models of noise-induced cochlear synaptopathy.

Long-Term Variability of Distortion-Product Otoacoustic Emissions in Infants and Children and Its Relation to Pediatric Ototoxicity Monitoring

OBJECTIVE

Distortion-product otoacoustic emissions (DPOAEs) provide a rapid, noninvasive measure of outer hair cell damage associated with chemotherapy and are a key component of pediatric ototoxicity monitoring. Serial monitoring of DPOAE levels in reference to baseline measures is one method for detecting ototoxic damage. Interpreting DPOAE findings in this context requires that test-retest differences be considered in relation to normal variability, data which are lacking in children. This study sought to (1) characterize normal test-retest variability in DPOAE level over the long time periods reflective of pediatric chemotherapy regimens for a variety of childhood ages and f2 primary frequencies using common clinical instrumentation and stimulus parameters; (2) develop level-shift reference intervals; and (3) account for any age-related change in DPOAE level or measurement error that may occur as the auditory system undergoes maturational change early in life.

DESIGN

Serial DPOAE measurements were obtained in 38 healthy children (25 females and 13 males) with normal hearing and ranging in age from one month to 10 years at the initial (baseline) visit. On average, children were tested 5.2 times over an observation period of 6.5 months. Data were collected in the form of DP grams, in which DPOAE level was measured for f2 ranging from 1.4 to 10 kHz, using a fixed f2/f1 ratio of 1.22 and stimulus level of 65/55 dB SPL for L1/L2. Age effects on DPOAE level and measurement error were estimated using Bayesian regression of the longitudinal data. The raw and model-based distribution of DPOAE test-retest differences were characterized using means and standard error of the measurement for several ages and f2's.

RESULTS

DPOAE test-retest differences for the children in this study are at the high end of those previously observed in adults, as reflected in the associated shift reference intervals. Further, although we observe substantial child-specific variation in DPOAE level, the pattern of age-related changes is highly consistent across children. Across a wide range of f2's, DPOAE level decreases by 3 to 4 dB from 1 to 13 months of age followed by a more gradual decline of <1 dB/year. An f2 of 6 kHz shows the smallest decrease during the early rapid maturation period. DPOAE measurement error is fairly constant with age. It is 3 to 4 dB at most f2's and is greater (indicating poorer reliability) at 1.5, 8, and 10 kHz.

CONCLUSIONS

DPOAE level decreases with childhood age, with the greatest changes observed in the first year of life. Maturational effects during infancy and greater measurement error at very low and high f2's affect test-retest variability in children. An f2 of 6 kHz shows minimal maturation and measurement error, suggesting it may be an optimal sentinel frequency for ototoxicity monitoring in pediatric patients. Once validated with locally developed normative data, reference intervals provided herein could be used to determine screen fail criteria for serial monitoring using DPOAEs. Employing state-of-the-art calibration techniques might reduce variability, allowing for more sensitive screen fail criteria.

Intracochlear distortion products are broadly generated by outer hair cells but their contributions to otoacoustic emissions are spatially restricted

Detection of low-level sounds by the mammalian cochlea requires electromechanical feedback from outer hair cells (OHCs). This feedback arises due to the electromotile response of OHCs, which is driven by the modulation of their receptor potential caused by the stimulation of mechano-sensitive ion channels. Nonlinearity in these channels distorts impinging sounds, creating distortion-products that are detectable in the ear canal as distortion-product otoacoustic emissions (DPOAEs). Ongoing efforts aim to develop DPOAEs, which reflects the ear's health, into diagnostic tools for sensory hearing loss. These efforts are hampered by limited knowledge on the cochlear extent contributing to DPOAEs. Here, we report on intracochlear distortion products (IDPs) in OHC electrical responses and intracochlear fluid pressures. Experiments and simulations with a physiologically motivated cochlear model show that widely generated electrical IDPs lead to mechanical vibrations in a frequency-dependent manner. The local cochlear impedance restricts the region from which IDPs contribute to DPOAEs at low to moderate intensity, which suggests that DPOAEs may be used clinically to provide location-specific information about cochlear damage.

Phonemically Balanced Arabic Monosyllabic Word Lists for Speech Audiometry Testing in Jordan

BACKGROUND

 Many of the Arabic monosyllabic word lists that are currently available in the literature have some limitations and drawbacks. Some of these available lists include word structures that are not consonant-nucleus-consonant (CNC) such as cluster and disyllabic word structures. Other lists have poor phonetic or phonemic distribution balance and do not represent some phoneme appropriately in each list.

PURPOSE

 The purpose of the present study is to create and validate eight digitally recorded lists of phonemically balanced CNC words that represent all Arabic phonemes, to be used in the evaluation of word recognition score (WRS) of Jordanian Arabic-speaking adults. These lists should be easily adapted by other Arab countries because of the simplicity of the words, and the balanced inclusion of all the Arabic phonemes.

RESEARCH DESIGN

 The present study is a prospective cross-sectional study.

STUDY SAMPLE

 Thirty-one (23 females, 8 males) normal hearing and healthy young adults (18-29 years old) participated in the present study. All participants were native speakers of Jordanian Arabic and had no history of ear disease or surgery.

LISTS

 The authors created all possible combinations of Arabic CNC words, and then created eight phonemically balanced lists with 26 words in each list. Each consonant was presented only once at the beginning of a word and once at the end of a word in each list. The lists were recorded using a Jordanian male voice and the intensity of each word was digitally calibrated.

DATA COLLECTION AND ANALYSIS

 The pure tone average (PTA) of 0.5, 1, 2, 4 kHz was calculated for each participant, and the WRS was obtained for each intensity level in the range of -10 to 55 dB SL (ref. PTA) in 5 dB steps.

RESULTS

 No significant difference between right and left ear WRS was found at any intensity level. The WRSs from both ears were averaged and used in the repeated measure analysis of variance. Performance-intensity functions for all the lists showed some small but statistically significant differences between lists. However, none of these differences were clinically significant (<4%). All the lists showed WRS exceeding 96% at 40 dB SL, and none of the lists showed statistically significant improvement in WRS beyond 40 dB SL.

CONCLUSION

 The present study provides eight lists of recorded and calibrated CNC word lists. The obtained PI functions showed that these lists are suitable for Jordanian Arabic speaking adults. These lists can be easily generalized to other Arab countries after conducting the required follow-up research.

The role of the medial olivocochlear reflex in psychophysical masking and intensity resolution in humans: a review

This review addresses the putative role of the medial olivocochlear (MOC) reflex in psychophysical masking and intensity resolution in humans. A framework for interpreting psychophysical results in terms of the expected influence of the MOC reflex is introduced. This framework is used to review the effects of a precursor or contralateral acoustic stimulation on 1) simultaneous masking of brief tones, 2) behavioral estimates of cochlear gain and frequency resolution in forward masking, 3) the buildup and decay of forward masking, and 4) measures of intensity resolution. Support, or lack thereof, for a role of the MOC reflex in psychophysical perception is discussed in terms of studies on estimates of MOC strength from otoacoustic emissions and the effects of resection of the olivocochlear bundle in patients with vestibular neurectomy. Novel, innovative approaches are needed to resolve the dissatisfying conclusion that current results are unable to definitively confirm or refute the role of the MOC reflex in masking and intensity resolution.

Test-retest reliability of distortion-product thresholds compared to behavioral auditory thresholds

When referred to baseline measures, serial monitoring of pure-tone behavioral thresholds and distortion-product otoacoustic emissions (DPOAEs) can be used to detect the progression of cochlear damage. Semi-logarithmic DPOAE input-output (I/O) functions enable the computation of estimated distortion-product thresholds (EDPTs) by means of linear regression, a metric that provides a quantitative estimate of hearing loss due to cochlear-amplifier degradation. DPOAE wave interference and a suboptimal choice of stimulus levels limit the accuracy of EDPTs. This work identifies the test-retest reliability of EDPTs derived from short-pulse DPOAE level maps (EDPT_LM), a method that circumvents limitations associated with both wave interference and suboptimal choice of stimulus levels. The test-retest reliability was compared to that of EDPTs derived from semi-logarithmic I/O functions (EDPT_I/O) and that of behavioral thresholds acquired with pure-tone audiometry (PTA) and modified Békésy tracking audiometry (TA) to provide a foundation for identifying and interpreting significant threshold shifts. The DPOAE-based auditory thresholds (EDPT_LM and EDPT_I/O) and behavioral thresholds (PTA and TA) were recorded seven times within three months at 14 frequencies with f₂ = 1-14 kHz in 20 ears from ten subjects with normal hearing (4PTA_0.5-4kHz < 20 dB HL). To obtain EDPT_LM, short-pulse DPOAEs were recorded using 21 L₁,L₂ pairs. Reconstruction of DPOAE growth behavior as a function of L₁ and L₂ using nonlinear curve fitting enabled the derivation of EDPT_LM for each frequency. Test-retest reliability was determined using three different approaches: 1) centered thresholds, 2) average threshold differences, and 3) average absolute threshold differences, between each possible test session (N = 21). Test-retest reliability based on centered thresholds and average threshold differences showed no statistically significant difference between EDPT_LM, EDPT_I/O, PTA, and TA for the pooled analysis incorporating all stimulus frequencies. Average absolute threshold differences presented small but significant differences in test-retest reliability with median values of 3.00 dB for PTA, 3.20 dB for TA, 3.34 dB for EDPT_LM, and 3.51 dB for EDPT_I/O. A considerable frequency dependence of test-retest reliability was found; namely, the highest test-retest reliability was for EDPT_LM at f₂ = 11 - 14 kHz. Otherwise, at lower frequencies, the highest test-retest reliability was for TA at f₂ =1 - 2 kHz. Overall, the test-retest reliability of EDPT_LM was better than that of EDPT_I/O and was similar to that for behavioral thresholds. Hence, deriving EDPT_LM from individual level maps is a promising and sensitive method for objectively monitoring the state of the cochlea. Furthermore, the detection of an equidirectional threshold change at a single frequency in both EDPT_LM and TA might allow reducing the threshold shift as indication of a follow-up examination from the clinical standard of 10 dB down to 5 dB. This stricter indicator might be beneficial when monitoring cochlear damage, for example ototoxicity, in the presence of (remnant) cochlear amplification at baseline.

Cochlear Synaptopathy due to Mutations in OTOF Gene May Result in Stable Mild Hearing Loss and Severe Impairment of Speech Perception

OBJECTIVES

Congenital profound hearing loss with preserved cochlear outer hair cell activity (otoacoustic emissions and cochlear microphonic) is the most common phenotype associated with mutations in the OTOF gene. The aim of this study was to investigate the pathophysiological mechanisms behind the auditory dysfunction in five patients (2 adults and 3 children) carrying biallelic mutations in OTOF, who showed an uncommon phenotype of mild hearing impairment associated with severe difficulties in speech perception and delay of language development.

DESIGN

Patients underwent audiometric assessment with pure-tone and speech perception evaluation, and otoacoustic emissions and auditory brainstem response recording. Cochlear potentials were recorded in all subjects through transtympanic electrocochleography in response to clicks delivered in the free field from 120 to 60 dB peak equivalent SPL and were compared to recordings obtained from 20 normally hearing controls and from eight children with profound deafness due to mutations in the OTOF gene. Three patients out of five underwent unilateral cochlear implantation. Speech perception measures and electrically evoked auditory nerve potentials were obtained within 1 year of cochlear implant use.

RESULTS

Pathogenic mutations in the two alleles of OTOF were found in all five patients, and five novel mutations were identified. Hearing thresholds indicated mild hearing loss in four patients and moderate hearing loss in one. Distortion product otoacoustic emissions were recorded in all subjects, whereas auditory brainstem responses were absent in all but two patients, who showed a delayed wave V in one ear. In electrocochleography recordings, cochlear microphonics and summating potentials showed normal latency and peak amplitude, consistently with preservation of both outer and inner hair cell activity. In contrast, the neural compound action potential recorded in normally hearing controls was replaced by a prolonged, low-amplitude negative response. No differences in cochlear potentials were found between OTOF subjects showing mild or profound hearing loss. Electrical stimulation through the cochlear implant improved speech perception and restored synchronized auditory nerve responses in all cochlear implant recipients.

CONCLUSIONS

These findings indicate that disordered synchrony in auditory fiber activity underlies the impairment of speech perception in patients carrying biallelic mutations in OTOF gene who show a stable phenotype of mild hearing loss. Abnormal nerve synchrony with preservation of hearing sensitivity is consistent with selective impairment of vesicle replenishment at the ribbon synapses with relative preservation of synaptic exocytosis. Cochlear implants are effective in restoring speech perception and synchronous activation of the auditory pathway by directly stimulating auditory fibers.

Audiologic Profiles of Children With Otitis Media With Effusion

OBJECTIVES

To describe the impact of effusion volume, viscosity, and purulence on the audiologic profiles of children with otitis media with effusion.

DESIGN

Fifty-one ears from children between the ages of 8 months and 11 years who had a diagnosis of otitis media with effusion and were scheduled for tympanostomy tube placement were recruited from medical clinics. The control group consisted of 17 ears from children between the ages of 10 months and 11 years without a recent history of otitis media and were recruited from a database of research volunteers. Participants received a comprehensive audiologic testing battery consisting of tympanometry, otoacoustic emissions, behavioral audiometric thresholds, and auditory brainstem response testing. For children with otitis media, this testing battery occurred 1 to 2 days before surgery. Middle ear effusions were characterized and collected on the day of surgery during tympanostomy tube placement from ears with otitis media with effusion. The comprehensive audiologic testing battery was completed postoperatively as well for most participants.

RESULTS

Effusion volume, categorized in each ear as clear, partial, or full, effected the audiologic results. Ears with full effusions had moderate hearing losses, few to no measurable otoacoustic emissions, and delayed Wave V latencies. Ears with partial effusions and clear ears both had slight to mild hearing losses and normal Wave V latencies, though ears with partial effusions had fewer measurable otoacoustic emissions than clear ears. Normal-hearing control ears with no recent history of otitis media with effusion demonstrated normal audiometric thresholds, present otoacoustic emissions, and normal Wave V latencies. Repeat postoperative testing demonstrated improvements in audiologic testing results for all of the otitis media with effusion volume groups, with no significant differences remaining between the three otitis media with effusion groups. However, significant differences between otitis media with effusion ears and normal-hearing control ears persisted postoperatively, with otitis media with effusion ears demonstrating significantly poorer audiometric thresholds and reduced otoacoustic emissions as compared to normal control ears. The effect of effusion viscosity and purulence could not be systematically evaluated because minimal variability in effusion viscosity and purulence was observed in our sample, with nearly all effusions being mucoid and nonpurulent.

CONCLUSIONS

Effusion volume observed at the time of tympanostomy tube surgery was found to play a significant role in outcomes and responses on a range of audiologic tests that compose the standard clinical pediatric audiologic assessment battery. Full middle ear effusions were associated with a moderate hearing loss, and few to no measurable otoacoustic emissions were detected. Ears with a recent diagnosis of otitis media with effusion but clear at the time of tympanostomy tube placement had less hearing loss and a greater number of present otoacoustic emissions than ears with full or partial effusions but were still found to have poorer hearing sensitivity than the healthy control ears. Differences between ears with otitis media with effusion and healthy control ears persisted on postoperative assessments of otoacoustic emissions and audiometric thresholds, though there were no remaining effects of the presurgical effusion volume group.

The Immediate and Long-Term Impact of Military Aircraft Noise on Hearing: A Cross-Sectional Comparison of Fighter Pilots and Ground Staff

We examined the immediate and long-term impacts of military aircraft noise exposure on noise-induced hearing loss (NIHL) in fighter pilots and ground staff. We recruited 40 pilots, 40 ground staff, and 136 age-matched controls; all participants underwent hearing tests, including conventional pure-tone audiometry (PTA) (0.25–8.0 kHz), extended high-frequency (EHF) audiometry (9.0–18.0 kHz), and distortion-product otoacoustic emission (DPOAE) as a recent reference. A subsequent hearing test immediately after flight-mission noise exposure was requested. The results revealed higher recent hearing thresholds in pilots and ground staff than in controls. Threshold shifts at many octave band frequencies were also significantly elevated in ground staff. The grouped frequency threshold was significantly elevated in the 4–8 kHz high-frequency range. After a single flight-mission noise exposure, both ground staff and pilots showed decreased signal-to-noise ratios for DPOAE (1–8 kHz), whereas only ground staff showed significantly elevated left-ear hearing thresholds at 3, 11.2, and 12.5 kHz by conventional and EHF PTA. Fighter pilots and ground staff serve in hazardous noise-exposed environments that cause hearing damage and subsequent NIHL, but ground staff may be more vulnerable. A comprehensive hearing conservation program should be implemented to protect high-risk service members, and especially ground staff, from high-intensity noise exposure.

Feasibility of a hearing screening programme using DPOAEs in 3-year-old children in South Auckland

OBJECTIVES

In New Zealand (NZ), permanent hearing loss is associated with higher levels of socioeconomic deprivation, and is more prevalent amongst Māori and Pacific than NZ European children. Many of these hearing losses are detected through newborn hearing screening, however there is a need to screen children again later, to look for childhood hearing losses that are either late-onset, progressive, or acquired. This study evaluated the feasibility of implementing an objective screening protocol that includes otoscopy, distortion product otoacoustic emission screening (DPOAEs), and tympanometry. It also evaluated the feasibility of using Early Learning Centres (ELCs) to contact families, recruit, and test 3-year-old children from an area of high socioeconomic deprivation in Auckland, New Zealand.

METHODS

Sixty-one 3-year-old children were recruited from ELCs within the Counties Manukau District Health Board (CMDHB) region which services the geographical area of South Auckland. The first part of the screening protocol consisted of otoscopy, DPOAEs, and tympanometry. Children identified with hearing loss and/or middle ear problems were either referred directly to Otolaryngology/Audiology at the local hospital or invited back for a re-screen 4-8 weeks later. Children who were referred from the screening were followed up to track and document their subsequent clinical pathway through the public health system.

RESULTS

Mean overall time for the screening protocol was 4.1 minutes. The combination of otoscopy, DPOAEs, and tympanometry was well accepted by the 3-year-old children. DPOAE amplitude and signal-to-noise ratio results significantly differentiated between different tympanometry results, providing support for this combination of measures to accurately screen for hearing loss and/or middle ear disease. Thirty-eight of the 61 children (62%) passed the screening protocol. Of the remaining 23 children, five were referred to the hospital after not passing the screening, but following more in-depth audiological testing, were discharged with normal hearing. Six children referred to the hospital were diagnosed with varying degrees of conductive hearing loss, and two of the six received grommet insertion surgery. The remaining 12 children who were referred to the hospital were lost to follow-up, highlighting challenges for the families to successfully navigate the current public health system.

CONCLUSION

This study demonstrates that identifying hearing loss and ear disease in 3-year-old children in the pre-school setting is feasible. A number of barriers were identified in the current health system that contribute to a large proportion of children referred with suspected hearing loss and ear disease being unsuccessful in accessing Otolaryngology/Audiology clinical care through the local hospital.

Hearing Norton Sound: community involvement in the design of a mixed methods community randomized trial in 15 Alaska Native communities

Community involvement is important in good research practice. We led a community-based study to improve early detection and treatment of childhood hearing loss in rural Alaska. This study evaluated a cell phone-based hearing screening process and compared a new telemedicine specialty referral pathway to the standard primary care referral pathway. The study included community involvement, engagement, and participation from the very beginning to inform how to best design the trial. We obtained insight and feedback from community members through involvement of a core stakeholder team and through community engagement and participation in focus groups and community events. Feedback received through community involvement and participation influenced the design of the trial at key decision points. Community member guidance shaped the research question, the outcomes to be measured, and the procedures for completing the project, such as participant recruitment. This study offers an example of community involvement, engagement and participation that could be mirrored in future research to maintain the interests of participating communities. Background Effective systems for early identification and treatment of childhood hearing loss are essential in rural Alaska, where data indicate a high prevalence of childhood ear infections and hearing loss. However, loss to follow-up from school hearing screening programs is pervasive. The Hearing Norton Sound study was a mixed methods community randomized controlled trial that was developed to address this gap. The study engaged community members and participants in the design of the trial, including involvement of stakeholders as collaborators. Methods Community engagement and participation in research design occurred through focus groups and through the integration of stakeholders into the study team. Representation was cross-sectoral, involving individuals from multiple levels of the school and health system, as well as community members from each of the 15 communities. Feedback obtained between April 2017 and August 2017 informed the final design of the randomized trial, which began enrollment of children in October 2017 and concluded in March 2019. Results Stakeholder involvement and community participation shaped the design of specific trial elements (research question; comparators; outcomes and measures; telemedicine protocols; and recruitment and retention). Community involvement was strengthened by the use of multiple modalities of involvement and by the positionality of lead stakeholders on the study team. Conclusions This study highlights the effectiveness of multifaceted stakeholder involvement and participation in the design of health research conducted within Alaska Native communities. It offers an example of involvement and reporting that could be mirrored in future research in order to protect and further the interests of the participating community. Trial registration ClinicalTrials.gov, NCT03309553 , First registered 10/9/2017.

Identifying three otopathologies in humans

OBJECTIVES

Hearing-in-noise (HIN) is a primary complaint of both the hearing impaired and the hearing aid user. Both auditory nerve (AN) function and outer hair cell (OHC) function are thought to contribute to HIN, but their relative contributions are still being elucidated. OHCs play a critical role in HIN by fine tuning the motion of the basilar membrane. Further, animal studies suggest that cochlear (auditory) synaptopathy, which is the loss of synaptic contact between hair cells and the AN, may be another cause of HIN difficulty. While there is evidence that cochlear synaptopathy occurs in animal models, there is debate as to whether cochlear synaptopathy is clinically significant in humans, which may be due to disparate methods of measuring noise exposure in humans and our high variability in susceptibility to noise damage. Rather than use self-reported noise exposure to define synaptopathic groups, this paper assumes that the general population exhibits a range of noise exposures and resulting otopathologies and defines cochlear synaptopathy "operationally" as low CAP amplitude accompanied by normal DPOAE levels in persons with low pure tone averages. The first question is whether the standard audiogram detects AN dysfunction and OHC dysfunction? The second question is whether HIN performance is primarily dependent on AN function, OHC function, or both functions?

DESIGN

Adult subjects have been recruited to participate in an ongoing study and variables such as age, self-reported gender, pure tone audiometry (0.25-20 kHz), subjective perception of HIN difficulty, Quick Speech-in Noise (QuickSIN) test, 45% time compressed word recognition (WR) in 10% reverberation and WR in the presence of ipsilateral speech-weighted noise have been collected. These variables were correlated with OHC function measured by distortion-product otoacoustic emission (DPOAE) signal to-noise-ratio (SNR), and AN function measured by compound action potential (CAP) peak amplitude and ratio to summating potential measured using electrocochleography.

RESULTS

Synaptopathy, by this operational definition, may be present in as many as 30% of individuals with normal hearing. Persons hearing within normal limits may exhibit HIN difficulties, and persons with hearing within normal limits may exhibit two distinct types of otopathologies undetected by the standard audiogram (a.k.a. hidden hearing loss) namely operational cochlear synaptopathy and OHC dysfunction. AN untuning secondary to OHC dysfunction is a third otopathology that occurs in subjects with a Mild-Moderate sensorineural hearing loss (SNHL). Clinical norms for each of these otopathologies are presented. Finally, the data show that operational cochlear synaptopathy does not correlate with HIN dysfunction. Rather, HIN performance is primarily governed by OHC function, while AN untuning also plays a lesser but statistically significant role.

CONCLUSIONS

The results of this study suggest the following: (1) persons hearing within normal limits may exhibit HIN difficulties; (2) persons hearing within normal limits may exhibit undetected otopathologies, namely AN dysfunction and OHC dysfunction; (3) AN untuning secondary to OHC dysfunction occurs in subjects with Mild-Moderate SNHL; (4) HIN performance is primarily governed by OHC function rather than AN function.

A clinical comparison of DPOAE fine structure reduction methods

OBJECTIVE

To evaluate two real-time methods for reducing distortion product otoacoustic emission (DPOAE) fine structure in terms of DPOAE amplitude and fine structure depth.

DESIGN

A prospective, repeated-measures design was used to assess DPOAE characteristics in response to a conventional stimulation method (Conv.), as well as for methods implementing either a generic suppressor tone (Supp.) or frequency modulation of the f₂ primary tone (FM).

STUDY SAMPLE

Eighty-three young adults (58 females) between the ages of 20 and 34 years with normal hearing completed testing for this study.

RESULTS

Use of the Conv. and FM methods resulted in consistently higher DPOAE levels relative to the Supp. method, with average advantages of 6 and 5 dB, respectively. For all methods, increased fine structure depth was observed for stimulation with lower level (25-45 dB SPL) and lower frequency (1000-3000 Hz) primary tones. Finally, use of the Supp. and FM methods resulted in significantly decreased fine structure depth relative to the Conv. method.

CONCLUSION

Through frequency modulation of the f₂ primary tone, it was possible to reduce the depth of fine structure across a clinically meaningful range of stimulation levels and frequencies without concomitant reduction in DPOAE amplitude.

Estimating Hearing Thresholds From Stimulus-Frequency Otoacoustic Emissions

It is of clinical interest to estimate pure-tone thresholds from potentially available objective measures, such as stimulus-frequency otoacoustic emissions (SFOAEs). SFOAEs can determine hearing status (normal hearing vs. hearing loss), but few studies have explored their further potential in predicting audiometric thresholds. The current study investigates the ability of SFOAEs to predict hearing thresholds at octave frequencies from 0.5 to 8 kHz. SFOAE input/output functions and pure-tone thresholds were measured from 230 ears with normal hearing and 737 ears with sensorineural hearing loss. Two methods were used to predict hearing thresholds. Method 1 is a linear regression model; Method 2 proposed in this study is a back propagation (BP) network predictor built on the bases of a BP neural network and principal component analysis. In addition, a BP network classifier was built to identify hearing status. Both Methods 1 and 2 were able to predict hearing thresholds from 0.5 to 8 kHz, but Method 2 achieved better performance than Method 1. The BP network classifiers achieved excellent performance in determining the presence or absence of hearing loss at all test frequencies. The results show that SFOAEs are not only able to identify hearing status with great accuracy at all test frequencies but, more importantly, can predict hearing thresholds at octave frequencies from 0.5 to 8 kHz, with best performance at 0.5 to 4 kHz. The BP network predictor is a potential tool for quantitatively predicting hearing thresholds, at least at 0.5 to 4 kHz.

Maximising the ability of stimulus-frequency otoacoustic emissions to predict hearing status and thresholds using machine-learning models

OBJECTIVE

This study aimed to maximise the ability of stimulus-frequency otoacoustic emissions (SFOAEs) to predict hearing status and thresholds based on machine-learning models.

DESIGN

SFOAE data and audiometric thresholds were collected at octave frequencies from 0.5 to 8 kHz. Support vector machine, k-nearest neighbour, back propagation neural network, decision tree, and random forest algorithms were used to build classification models for status identification and to develop regression models for threshold prediction.

STUDY SAMPLE

About 230 ears with normal hearing and 737 ears with sensorineural hearing loss.

RESULTS

All classification models yielded areas under the receiver operating characteristic curve of 0.926-0.994 at 0.5-8 kHz, superior to the previous SFOAE study. The regression models produced lower standard errors (8.1-12.2 dB, mean absolute errors: 5.53-8.97 dB) as compared to those for distortion-product and transient-evoked otoacoustic emissions previously reported (8.6-19.2 dB).

CONCLUSIONS

SFOAEs using machine-learning approaches offer promising tools for the prediction of hearing capabilities, at least at 0.5-4 kHz. Future research may focus on further improvements in accuracy and reductions in test time to improve clinical utility.

An intracochlear DP-gram: Proof of principle in noise-damaged rabbits

Distortion-product otoacoustic emissions (DPOAEs) can be used to assess cochlear damage and are often evaluated by generating a DP-gram in which 2f₁-f₂ DPOAE levels are plotted as a function of the higher-frequency primary at f₂. DPOAEs are derived from the reverse propagation of distortion-product (DP) wavelets from their intracochlear sites of generation to emerge as measurable acoustic signals in the outer ear canal. However, at least, some of these same wavelets also propagate within the cochlea in the normal forward direction to the DP-frequency (f_dp) place, where they appear as intracochlear distortion products (iDPs). Depending on several factors, especially, the extent to which DP wavelets add or cancel with each other in phase, one might expect iDPs to differ from DPOAEs in their ability to map the frequency pattern of cochlear damage. In the present study, the behavior of 2f₁-f₂ iDPs was inferred by interacting a probe tone (f₃) with the iDP of interest to produce a 'secondary' DPOAE (i.e., DPOAE^2ry), which was then used to infer the level of 2f₁-f₂ iDPs as a function of the f₂-test frequency, thus, constituting a newly developed iDP-gram. To determine the feasibility of and potential applications for the iDP-gram procedure, noise-induced cochlear damage was assessed in two 'test' rabbits, one of which exhibited a well-defined punctate loss in their DP-gram, while the other exhibited a broader V-shaped loss. To validate the iDP-gram procedure, standard DP-grams were simultaneously collected and compared to their iDP-gram counterparts. Cochlear damage was independently assessed using auditory brainstem responses (ABRs) describing threshold-shift patterns to which both DP-gram types could be compared. Each DP-gram variety, to some extent, was able to detect a punctate loss in one rabbit and a broader V-shaped loss in the other. For the punctate-loss subject, the standard DP-gram showed a more generalized loss across test frequencies, while iDP-grams showed several localized notches superimposed on the generalized-loss pattern. In general, for the V-shaped loss pattern, both DP-gram types performed very well at detecting the large loss, with the lower primary-tone levels being most sensitive. At the narrow primary-tone ratios of f₂/f₁=1.05, standard DP-grams were unable to detect either loss pattern, while for the punctate loss, they paradoxically showed enhancement. Notably, the simultaneously collected iDP-grams performed favorably at the narrow-ratio setting, which is consistent with the notion that DPs travelling toward the 2f₁-f₂ f_dp place are not subject to the cancellation of wavelets typical for narrow primary-ratio conditions that can confound measures of DPs moving towards the ear canal to emerge as DPOAEs.

Cochlear synaptopathy: new findings in animal and human research

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.

Evoked Potentials Reveal Noise Exposure-Related Central Auditory Changes Despite Normal Audiograms

Purpose Complaints of auditory perceptual deficits, such as tinnitus and difficulty understanding speech in background noise, among individuals with clinically normal audiograms present a perplexing problem for audiologists. One potential explanation for these "hidden" auditory deficits is loss of the synaptic connections between the inner hair cells and their afferent auditory nerve fiber targets, a condition that has been termed cochlear synaptopathy. In animal models, cochlear synaptopathy can occur due to aging or exposure to noise or ototoxic drugs and is associated with reduced auditory brainstem response (ABR) wave I amplitudes. Decreased ABR wave I amplitudes have been demonstrated among young military Veterans and non-Veterans with a history of firearm use, suggesting that humans may also experience noise-induced synaptopathy. However, the downstream consequences of synaptopathy are unclear. Method To investigate how noise-induced reductions in wave I amplitude impact the central auditory system, the ABR, the middle latency response (MLR), and the late latency response (LLR) were measured in 65 young Veterans and non-Veterans with normal audiograms. Results In response to a click stimulus, the MLR was weaker for Veterans compared to non-Veterans, but the LLR was not reduced. In addition, low ABR wave I amplitudes were associated with a reduced MLR, but with an increased LLR. Notably, Veterans reporting tinnitus showed the largest mean LLRs. Conclusions These findings indicate that decreased peripheral auditory input leads to compensatory gain in the central auditory system, even among individuals with normal audiograms, and may impact auditory perception. This pattern of reduced MLR, but not LLR, was observed among Veterans even after statistical adjustment for sex and distortion product otoacoustic emission differences, suggesting that synaptic loss plays a role in the observed central gain. Supplemental Material https://doi.org/10.23641/asha.11977854.

Auditory function and prevalence of specific ear and hearing related pathologies in the general population at age 70

Objective: To describe the auditory function in early old age in detail based on both psychoacoustic and physiological measures, and to investigate the prevalence of specific audiological and otological pathologies.Design: An unscreened subsample from a population-based geriatric investigation was examined with otoscopy; tympanometry; pure-tone audiometry; word-recognition-in-noise test; distortion-product otoacoustic emissions; and auditory-evoked brainstem responses. Audiometric subtypes and diagnoses were established based on set criteria. The association between word scores and ABR was examined with linear regression analysis.Study Sample: 251 persons aged 70 (113 men, 138 women, born in 1944) that were representative of the inhabitants of the city of Gothenburg.Results: The prevalence of conductive pathology was 2% versus 49% for cochlear and 2% for auditory-neural pathology. Four percent had indeterminate type. Cochlear dysfunction was present in the majority of ears and around 20% performed worse-than-expected on speech testing. Poor performance on the speech in noise test was associated with prolonged interpeak latency interval of ABR waves I-V.Conclusion: Specific otological and audiological pathologies, other than cochlear hearing loss, are rare in the general population at age 70. Additionally, there is subtle evidence of age-related decline of the auditory nerve. Longitudinal follow-up would be of great interest.

Auditory brainstem response demonstrates that reduced peripheral auditory input is associated with self-report of tinnitus

Tinnitus is one of the predicted perceptual consequences of cochlear synaptopathy, a type of age-, noise-, or drug-induced auditory damage that has been demonstrated in animal models to cause homeostatic changes in central auditory gain. Although synaptopathy has been observed in human temporal bones, assessment of this condition in living humans is limited to indirect non-invasive measures such as the auditory brainstem response (ABR). In animal models, synaptopathy is associated with a reduction in ABR wave I amplitude at suprathreshold stimulus levels. Several human studies have explored the relationship between wave I amplitude and tinnitus, with conflicting results. This study investigates the hypothesis that reduced peripheral auditory input due to synaptic/neuronal loss is associated with tinnitus. Wave I amplitude data from 193 individuals [43 with tinnitus (22%), 150 without tinnitus (78%)], who participated in up to 3 out of 4 different studies, were included in a logistic regression analysis to estimate the relationship between wave I amplitude and tinnitus at a variety of stimulus levels and frequencies. Statistical adjustment for sex and distortion product otoacoustic emissions (DPOAEs) was included. The results suggest that smaller wave I amplitudes and/or lower DPOAE levels are associated with an increased probability of tinnitus.

Observations of Distortion Product Otoacoustic Emission Components in Adults With Hearing Loss

OBJECTIVES

Distortion product otoacoustic emissions (DPOAEs) measured in the ear canal are composed of OAEs generated by at least two mechanisms coming from different places in the cochlea. Otoacoustic emission (OAE) models hypothesize that reduction of cochlear gain will differentially impact the components. The purpose of the current experiment was to provide preliminary data about DPOAE components in adults with hearing loss in relation to OAE models and explore whether evaluation of the relative amplitudes of generator and reflection components can enhance identification of hearing loss.

DESIGN

DPOAEs were measured from 45 adult ears; 21 had normal hearing (≤15 dB HL) and 24 with mild-to-severe sensorineural hearing loss (>15 dB HL). The higher frequency primary (f2) was swept logarithmically between 1500 and 6000 Hz, and f2/f1 was 1.22. The two equal-level primaries varied from 55 to 75 dB SPL in 5 dB steps. The swept primary procedure permitted the measurement of the amplitude and phase of the DPOAE fine structure and the extraction of the two major components (generator and reflection) by varying the predicted delays of the analysis windows.

RESULTS

DPOAE fine structure was reduced or absent in ears with hearing loss. DPOAE generator and reflection components were lower in ears with hearing loss than those with normal hearing, especially for the reflection component. Significant correlations were found between the generator component and hearing threshold but not between reflection levels and hearing threshold. Most ears with normal hearing had both components, but only a small number of ears with hearing loss had both components.

CONCLUSIONS

The reflection component is not recordable or low in level in ears with hearing loss, explaining the reduced or absent DPOAE fine structure. DPOAE generator components are also lower in level in ears with hearing loss than in ears without hearing loss. In ears that had both measurable generator and reflection components, the relationship between the two did not depend on the presence or absence of hearing loss. Because reflection components are not measurable in many ears with hearing thresholds >15 dB HL, stimuli that evoke other types of reflection emissions, such as stimulus-frequency or long-latency transient-evoked emissions, should be explored in conjunction with DPOAE generator components.

Cochlear Mechanisms and Otoacoustic Emission Test Performance

OBJECTIVES

This study aims to determine the impact of controlling cochlear-source mechanism on the accuracy with which auditory status is identified using otoacoustic emissions (OAEs) in two groups of subjects with normal hearing (NH) and subjects with mild to moderate hearing loss.

DESIGN

Data were collected from 212 subjects with NH and with mild to moderate hearing loss who fell into two categories based on a distortion product OAE (DPOAE) screening protocol: the uncertain-identification group (where errors were likely) and the certain-identification group (where errors were unlikely). DPOAE fine-structure patterns were recorded at intervals surrounding f2 = 1, 2 and 4 kHz (f2/f1 ratio = 1.22), with L2 = 35, 45, and 55 dB SPL (L1/L2 ratio = 10 dB). The discrete cosine transform was used to smooth fine structure, limiting the source contribution to the distortion source only. Reflection-source OAEs were also recorded using amplitude-modulated stimulus frequency OAEs (AM-SFOAE). Area under the relative operating characteristic (AROC) curve was used to quantify test accuracy when the source contribution was controlled versus the condition where both sources contribute. Additionally, failure rate, fixed at 5% for NH ears, as a function of behavioral-threshold category was evaluated.

RESULTS

When data for the entire subject group were examined, reducing the reflection-source contribution to the DPOAE did not result in better test performance than the best control condition at any frequency tested. When the subjects with NH were restricted to those with confirmed fine structure, AROC analyses indicated that reducing the reflection-source contribution resulted in several small increases in the accuracy (2%-5%) with which auditory status was identified relative to the best control condition. This improvement was observed for the lowest stimulus levels (i.e., L2 = 35 or 45 dB SPL). In this subset of subjects, distortion-source DPOAEs resulted in more accurate identification of mild hearing loss for a fixed false-positive rate of 5% in NH ears at lower L2's, conditions with poor accuracy in the larger group of subjects. The impact of controlling the source contribution on the identification of moderate losses was less clear in the reduced subject group, with some conditions where the distortion-source DPOAE was more accurate than the control condition and other conditions where there was no change. There was no evidence that reflection-source AM-SFOAEs more accurately identified ears with hearing loss when compared to any of the DPOAE conditions in either the large or reduced group of subjects.

CONCLUSION

While improvements in test accuracy were observed for some subjects and some conditions (e.g., mild hearing losses and low stimulus levels in the reduced subset of subjects), these results suggest that restricting cochlear source contribution by "smoothing" DPOAE fine structure is not expected to improve DPOAE test accuracy in a general population of subjects. Likewise, recording reflection-source OAEs using the AM-SFOAE technique would not be expected to more accurately identify hearing status compared to mixed- or single-source DPOAEs.

Emerging Distortion Product Otoacoustic Emission Techniques to Identify Preclinical Warning Signs of Basal Cochlear Dysfunction Due to Ototoxicity

Hundreds of medications commonly prescribed for anticancer treatments and some infections are known to cause hearing damage, referred to as ototoxicity. Preventing or minimizing ototoxicity is critical in order to preserve quality of life for patients receiving treatment and to reduce the societal burden of hearing loss. Current clinical evaluations are restricted to a limited frequency range (≤8 kHz); however, this approach does not permit the earliest detection of ototoxicity, most likely to be observed at the highest frequencies (9–20 kHz). Distortion product otoacoustic emissions (DPOAEs) offer a noninvasive, objective approach to monitor cochlear health in those unable to respond via conventional methods. The current report analyzes different DPOAE paradigms used in patients undergoing chemotherapy treatments with various platinum derivatives. Individualized serial monitoring protocols were completed at the highest frequencies with measurable DPOAEs. This allowed the exploration of potential clinical translation opportunities for further quantification of the earliest signs of underlying cochlear damage, which may go undetected with conventional methods. Clinical practice has the potential to be enhanced by emerging DPOAE applications, including targeted monitoring protocols and high-frequency stimuli to assess cochlear function, especially at the highest frequencies, and advanced calibration techniques to ensure the stability of serial measurements.

Subclinical conductive hearing loss significantly reduces otoacoustic emission amplitude: Implications for test performance

OBJECTIVES

Distortion product otoacoustic emissions (DPOAEs) are a time-efficient, non-invasive means of assessing the integrity of active inner ear mechanics. Unfortunately, the presence of even relatively minor conductive hearing loss (CHL) has been suggested to reduce the clinical utility of DPOAEs significantly. The primary aims of this study were to systematically evaluate the impact of CHL on DPOAE amplitude and to determine if ear-specific primary tone level manipulations can be used to mitigate CHL impact and recover DPOAE measurability.

METHODS

For 30 young adults (57 ears) with normal hearing, DPOAEs were obtained for f₂ = 1-6 kHz. Observed DPOAE amplitudes were used to generate ear- and frequency-specific models with the primary tone levels, L₁ and L_2, as inputs and predicted DPOAE amplitude, L_DP, as output. These models were then used to simulate the effect of CHL (0-15 dB), as well as L₁ manipulations (0-15 dB), on DPOAE measurability.

RESULTS

Mean L_DP for every CHL condition was significantly different from that for all other conditions (p = <.001), with a mean L_DP attenuation of 8.7 dB for every 5 dB increase in CHL. Mean DPOAE measurability in response to a standard clinical stimulation paradigm of L₁/L₂ = 65/55 (dB SPL) was determined to be 99%, 84%, 37%, and 9% in the presence of 0, 5, 10, and 15 dB CHL, respectively. In the presence of 10 dB CHL, altering L₁ resulted in an approximately 25% increase in DPOAE responses.

CONCLUSION

Subclinical CHL loss is sufficient to significantly impair DPOAE measurability in a meaningful proportion of otherwise healthy ears. However, through strategic alteration of primary tone levels, the clinician can mitigate CHL impact and at least partially recover DPOAE measurability.

Cochlear dysfunction evidenced by reduction of amplitude of otoacoustic responses in patients with congenital hypothyroidism

INTRODUCTION

The investigation of amplitudes of otoacoustic emissions in congenital hypothyroidism can provide information on cochlear function with more sensibility, when compared to other methods of auditory evaluation.

AIM

To investigate cochlear function through the amplitude of distortion product otoacoustic emissions in individuals with congenital hypothyroidism and to correlate with clinical aspects.

METHODS

An exploratory, analytical, cross-sectional study with a convenience sample, composed of 50 individuals with congenital hypothyroidism and a group of 42 individuals without the disease, mean age of 8.4 (±3.1) years. The subjects of the research were evaluated by means of tonal and speech audiometry, immittance and distortion product otoacoustic emissions (DPOAEs). Continuous variables were described as mean or median and standard deviation. The Spearman test evaluated the correlations between the variables.

RESULTS

Otoacoustic emission amplitudes were significantly reduced in the exposed group, with congenital hypothyroidism, when compared to the group of individuals without the disease, especially in the medium frequencies. The Spearman test showed a slight correlation between the amplitude values of the otoacoustic emissions of some frequencies and the variables: disease time, diagnostic age, irregular serum free thyroxine hormone levels and thyroid stimulating hormone, especially in the condition of less treatment, whose correlation was negative.

CONCLUSION

There was a correlation between the levels of signal amplitudes of otoacoustic emissions with clinical conditions and hormonal follow-up, suggesting probable subclinical auditory impairment in this population, as well as influence of some clinical aspects of congenital hypothyroidism on auditory function.