Transient Evoked Otoacoustic Emissions Research Articles

Covid-19 infection in pregnant women: Auditory evaluation in infants.

Recent studies showed that COVID-19 infection can affect cochleo-vestibular system. The possibility of a vertical transmission is controversial. Some studies suggested that it is possible but unlikely, others find no evidence of vertical transmission. The objective of this study was to investigate whether exposure to COVID-19 during pregnancy or at birth has an impact on the hearing of the offspring. As part of the national hearing screening program, we performed in all newborns between January 2022 and February 2023, TEOAEs (Transient Evoked Otoacoustic Emissions) at birth and at 3 months. For those "REFER" at the third month test, we performed aABR (Automatic Auditory Brainstem Response) at 6 months. We analysed separately result between infants born to COVID-positive mothers during pregnancy and those born to COVID-negative mothers. To statistical verify differences we performed "Chi-square test". We enrolled a total of 157 infants, of whom 16 were born to mothers who had a molecular PCR test positive for COVID-19. In the latter we tested a total of 32 ears and only 1 ear (3,1%) resulted "REFER". On the other hand, in the control group we tested a total of 282 ears and 22 (7,8%) were found to be "REFER". Our study showed no significant differences in audiological assessment between newborns exposed to COVID-19 infection during pregnancy or at birth compared to the unexposed group. However, further studies with a larger patient's sample will be necessary for a more comprehensive evaluation.

Psychometric Validation of a Hearing Screening Questionnaire for Preschoolers based on language development evaluation by caregivers.

This study aimed to validate three age-adjusted versions of a Hearing Screening Questionnaire for Preschoolers, in Brazilian Portuguese, based on parents' perception of their children's hearing and oral language. Psychometric validation was conducted on three questionnaires, each comprising nine items with Yes/No responses. Three items focused on hearing screening at birth, and six assessed hearing and oral language. The study included 152 parents and their children, who attended day care centers in Belo Horizonte, Brazil. The children were categorized into three age bands: 12 to 18 months, 19 to 35 months, and 36 to 48 months. Audiological assessments, including tympanometry, transient-evoked otoacoustic emissions (TOAE) and pure-tone audiometry (when applicable), were performed on the children. In case of abnormal findings in the previous exams, auditory brainstem response (ABR) testing was conducted. Descriptive data, false alarm, and false-negative analyses were carried out. Considering any type of hearing loss, whether unilateral or bilateral, the questionnaires showed a false-negative rate of 41.17% (7/17 children). However, when considering only bilateral hearing loss, the questionnaire showed a false alarm rate of 31.69% (45/142) and a false-negative rate of 30.0% (3/10). When focusing exclusively on sensorineural hearing loss, the questionnaire identified two children (1.31%), with a false-negative rate of 0% but a false-positive rate of 33.33%. Language-development oriented questionnaires allowed quick screening of potential hearing loss in preschoolers. This study found a robust hit rate with these questionnaires. Their validation signifies a promising and cost-effective tool for conducting hearing screenings in preschool children, especially in nations lacking a comprehensive school screening policy.The validated questionnaire affords an easy-to-apply, low-cost and effective instrument for preschool hearing screening.

Evaluation of cochlear and auditory brainstem functions in COVID-19 patients; a case control study

BackgroundMany viral infections can cause hearing loss due to affection of cochlear hair cells or neurogenic pathway. Although, the damage secondary to viral infections is mainly cochlear affection; auditory brainstem can be affected as well. It was predicted that SARS-COV-2 infection can similarly affect the auditory system. This study aimed to detect affection in auditory system and if present investigate the possible site of lesion (up to the level of the brain stem) in relation to COVID-19 infection.MethodsThis is a case control study, where the study group constituted of thirty adults, diagnosed with COVID-19 at least 2 weeks prior to testing and up to 6 months, without previous auditory complaints pre-COVID-19 or other risk factors that could affect the auditory pathway. Fifteen adult participants that were age and gender matched to the study group with no previous history of covid-19 infection constituted the control group. Audiological evaluations done to all participants were pure-tone and speech audiometry, tympanometry, transient-evoked otoacoustic emission with and without contralateral suppression and auditory brainstem response measurements.ResultsThe study group showed significantly worse pure tone thresholds at high frequencies 4 and 8 kHz (p < 0.01), significantly worse transient-evoked otoacoustic emission signal to noise ratio at 2800 Hz and 4000 Hz (p < 0.05) and significantly lower total suppression index (p<0.05). On the other hand, there was no significant difference between both groups in auditory brainstem response wave latencies (p > 0.05).ConclusionCOVID-19 had subtle effect on cochlear basal turn, and it is shown that the auditory efferent system may also be affected, while the auditory nerve and afferent brainstem pathways seems to be spared. Moreover, the absence of the symptoms of auditory dysfunction postcovid-19 does not guarantee normal auditory functions.

Audiologic and vestibular assessment in children and adolescents with transfusion dependent beta thalassemia major: The era of deferasirox film coated tablet

BackgroundHearing impairment has frequently been described in β-thalassemia patients with a significant impact on the patients’ quality of life. Most studies provided evidence of deferoxamine (DFO) dose-related ototoxicity, however, the data is scarce regarding deferasirox (DFX) as a sole iron chelator. AimWe aimed to assess the prevalence and risk factors of sensorineural hearing loss (SNHL) and vestibular dysfunction in regularly transfused β-thalassemia patients who had been treated with DFX film coated tablets. MethodsWe conducted a case control study on 57 transfusion dependent β-thalassemia patients with a mean age of 15.3 years who received DFX FCT as monotherapy for at least one consecutive year, and 57 healthy age and sex-matching controls. Comprehensive audiological evaluations using pure tone audiometry (PTA) and transient evoked otoacoustic emission (TEOAE) as well as vestibular evaluation using Video-nystagmography (VNG) were done. ResultsSNHL was identified in 12 patients (21.1 %) using PTA and a statistically significant difference was detected between controls and patients at 6 KHz and 12 KHz frequencies. A higher incidence of SNHL was detected using TEOAE, 22 patients (43.1 %) failed to pass TEOAE, with a statistically significant decrease in the signal at frequencies 1, 4 KHz bilaterally and at frequencies 1.5, 2 KHz in the right ear compared to controls. Canal paresis was detected in 21 (36.8 %) of thalassemic children using bithermal caloric test with significantly more unilateral weakness than control children (P = 0.008). We found no significant correlation between audio-vestibular dysfunction and age, sex, serum ferritin, frequency of blood transfusion and dose of DFX FCT in thalassemic children. ConclusionWe conclude that the incidence of SNHL and vestibular dysfunction was high among transfusion dependent β-thalassemia patients. Therefore, we recommend performing pre-treatment baseline audio-vestibular assessment and yearly audio-vestibular monitoring to early detect high risk patients and initiate timely management to prevent permanent damage.

NO AFTER-EFFECTS OF COVID-19 INFECTION IN TERMS OF STANDARD AUDIOLOGICAL TESTS

IntroductionCoronavirus disease (COVID-19), considered to be caused by a novel coronavirus (SARS-CoV-2), is an acute respiratory disease which was declared a pandemic by the World Health Organization. Previously published reports have shown contradictory findings on the involvement of the auditory system in individuals infected with COVID-19. The present study aims to assess auditory system functioning in individuals post-COVID-19 infection and compare the results with individuals without COVID-19 infection.Material and methodsParticipants in this study were 30 individuals who had experienced mild COVID-19 infection and 30 individuals who never had COVID-19. Participants were aged between 18 and 40 years. Testing was done 1 to 6 months after infection, and involved conventional and extended high-frequency audiometry, speech perception in quiet and at different signal-to-noise ratios (SPIN), transient evoked otoacoustic emissions (TEOAEs) in quiet and in the presence of contralateral noise, and auditory brainstem response (ABR) in the ipsilateral and contralateral mode.ResultsNone of the tests – pure-tone thresholds, speech perception in quiet and in noise, TEOAE with and without contralateral noise, and ABR – showed any significant difference between individuals who never had COVID-19 infection and those who had recovered from the infection. Both afferent and efferent auditory pathways showed normal findings in individuals post-COVID-19 infection.ConclusionsIndividuals who have been infected with mild COVID-19 did not show any significant deficit in any of the audiological tests, suggesting that the disease does not cause any permanent harm to the auditory system after the infection has subsided.

Analysis of audiological outcomes of children referred from a universal newborn hearing screening program over 9 years in Beijing, China

Universal newborn hearing screening (UNHS) and audiological diagnosis are crucial for children with congenital hearing loss (HL). The objective of this study was to analyze hearing screening techniques, audiological outcomes and risk factors among children referred from a UNHS program in Beijing. A retrospective analysis was performed in children who were referred to our hospital after failing UNHS during a 9-year period. A series of audiological diagnostic tests were administered to each case, to confirm and determine the type and degree of HL. Risk factors for HL were collected. Of 1839 cases, 53.0% were referred after only transient evoked otoacoustic emission (TEOAE) testing, 46.1% were screened by a combination of TEOAE and automatic auditory brainstem response (AABR) testing, and 1.0% were referred after only AABR testing. HL was confirmed in 55.7% of cases. Ears with screening results that led to referral experienced a more severe degree of HL than those with results that passed. Risk factors for HL were identified in 113 (6.1%) cases. The main risk factors included craniofacial anomalies (2.7%), length of stay in the neonatal intensive care unit longer than 5 days (2.4%) and birth weight less than 1500 g (0.8%). The statistical data showed that age (P < 0.001) and risk factors, including craniofacial anomalies (P < 0.001) and low birth weight (P = 0.048), were associated with the presence of HL. This study suggested that hearing screening plays an important role in the early detection of HL and that children with risk factors should be closely monitored.

Hearing Loss and Risk Factors in Very Low Birth Weight Infants.

The incidence of sensorineural hearing loss (SNHL) is still high in very low birth weight (VLBW) infants. The purpose of our study was to provide the prevalence rates of SNHL and to analyze the risk factors of hearing impairment and changes in hearing thresholds in a cohort of VLBW infants. A retrospective observational study was conducted in our neonatal intensive care unit (NICU) from 2012 to 2016. All VLBW infants included were screened by transient evoked otoacoustic emissions (TEOAEs) and diagnostic auditory brainstem response (ABR). In total, we enrolled 316 infants and SNHL was diagnosed in 68, leading to an early incidence of 21.5% as 36 infants out of 68 improved. Finally, SNHL was confirmed in 20 patients (6.3%) who needed hearing aids. They were significantly smaller, sicker, had longer hospitalizations, and received more ototoxic therapies. Logistic regression analysis showed that gestational age (GA) influenced the association between drugs and SNHL. The results underlined how the total exposure to antibiotics is significantly associated with SNHL, even after GA correction. In conclusion, GA, birth weight and, above all, the length and complexity of NICU stay quantify the risk of SNHL and should be considered at the individual level for parent counseling.

Heightened OAEs in young adult musicians: Influence of current noise exposure and training recency

Otoacoustic emissions (OAEs) are a non-invasive metric of cochlear function. Studies of OAEs in musicians have yielded mixed results, ranging from evidence of diminished OAEs in musicians—suggesting noise-induced hearing loss—to no difference when compared to non-musicians, or even a trend for stronger OAEs in musicians. The goal of this study was to use a large sample of college students with normal hearing (n = 160) to compare OAE SNRs in musicians and non-musicians and to explore potential effects of training recency and noise exposure on OAEs in these cohorts. The musician cohort included both active musicians (who at the time of enrollment practiced at least weekly) and past musicians (who had at least 6 years of training). All participants completed a questionnaire about recent noise exposure (previous 12 months), and a subset of participants (71 musicians and 15 non-musicians) wore a personal noise dosimeter for one week to obtain a more nuanced and objective measure of exposure to assess how different exposure levels may affect OAEs before the emergence of a clinically significant hearing loss. OAEs were tested using both transient-evoked OAEs (TEOAEs) and distortion-product OAEs (DPOAEs). As predicted from the literature, musicians experienced significantly higher noise levels than non-musicians based on both subjective (self-reported) and objective measures. Yet we found stronger TEOAEs and DPOAEs in musicians compared to non-musicians in the ∼1–5 kHz range. Comparisons between past and active musicians suggest that enhanced cochlear function in young adult musicians does not require active, ongoing musical practice. Although there were no significant relations between OAEs and noise exposure as measured by dosimetry or questionnaire, active musicians had weaker DPOAEs than past musicians when the entire DPOAE frequency range was considered (up to ∼16 kHz), consistent with a subclinical noise-induced hearing loss that only becomes apparent when active musicians are contrasted with a cohort of individuals with comparable training but without the ongoing risks of noise exposure. Our findings suggest, therefore, that separate norms should be developed for musicians for earlier detection of incipient hearing loss. Potential explanations for enhanced cochlear function in musicians include pre-existing (inborn or demographic) differences, training-related enhancements of cochlear function (e.g., upregulation of prestin, stronger efferent feedback mechanisms), or a combination thereof. Further studies are needed to determine if OAE enhancements offer musicians protection against damage caused by noise exposure.

Do Flights Affect Hearing in Hot Air Balloon Pilots?

This study aimed to reveal occupational effects on the hearing of hot air balloon (HAB) pilots and examine the relationship between the duration of experience and these effects. This study included 31 male HAB pilots and a control group of 32 male participants. Tympanometry, eustachian tube function (ETF) test, pure-tone audiometry, and transient evoked otoacoustic emission (TEOAE) tests were performed. Pure-tone audiometry results were significantly worse at 125, 500, and 6000 Hz in the right ear and 125, 500, 4000, and 6000 Hz in the left ear in the HAB group than the control group. Although tympanometry evaluation parameters did not differ between the HAB and control groups, ETF test was significantly worse in the HAB group than the controls bilaterally. TEOAE results were significantly worse at 1000, 2000, and 4000 Hz in the right ear and 4000 Hz in the left ear in the HAB group than the controls. There was a significant positive correlation for 125, 4000, 6000, and 8000 Hz between the duration of experience and right ear hearing thresholds. For the left ear, the duration of experience showed a significant positive correlation at 3000, 4000, 6000, and 8000 Hz. When the relationship between the duration of experience and TEOAE results was evaluated, a significant negative correlation was found at 4000 Hz in the left ear. In HAB pilots, in whom eustachian tube dysfunction is quite common, noise and high altitude affected hearing, especially low and high frequencies, and the duration of experience was found to be associated with hearing thresholds.

Hearing profile of recovered severe acute respiratory syndrome Coronavirus-2 (SARS-COV2) patients

BackgroundCoronaviruses are large, encapsulated RNA viruses that can infect both humans and animals and cause minor respiratory illnesses. In December 2019, numerous cases of pneumonia of unknown origin were reported in Wuhan, China. Coronavirus Disease 2019 (COVID-19), the cause of these cases, was discovered on January 6, 2020. The new coronavirus was declared an epidemic by the WHO on March, 2020. Several studies on COVID-19 have found that auditory complaints and hearing impairment can be detected using various tests.ObjectivesPure tone audiometry (PTA) and transient evoked otoacoustic emissions (TEOAEs) were used to assess hearing in recovered SARS-CoV-2 patients. Also, to compare the presence of patient's auditory complaints with the test findings.MethodsA case- control study was conducted, with each case and control group consisting of 58 people who were age and sex matched and ranged in age from 18 to 50 years. PTA, Extended PTA and, TEOAEs were used to evaluate hearing in both groups.ResultsPTA revealed a statistically significant difference in right ear thresholds at 250 Hz, 500 Hz, 4 kHz, and 8 kHz and left ear thresholds at 250 Hz, 4 kHz, 8 kHz, and 12.5 kHz between patients and controls. Additionally, a statistically significant difference in TEOAEs' overall reproducibility and amplitude between patients and controls was discovered. Affection for PTA and TEOAEs were related to the patient's complaints of hearing loss and tinnitus, respectively.ConclusionsWhether a patient is symptomatic or not, COVID-19 may have a negative impact on their hearing.

Robust estimation of synchronized spontaneous otoacoustic emission via singular value decomposition and optimal shrinkage.

We investigate matrix signal processing techniques for estimating synchronized spontaneous otoacoustic emission (OAE) in noise. Responses to repeated clicks are first stored in a matrix, and singular value decomposition is either applied in the time domain or the frequency domain after constructing a Hankel matrix at every frequency. The singular values are subject to optimal shrinkage (OS) which maximizes the signal-to-noise ratio. Human OAE data were analyzed, and the Hankel matrix method outperforms the time-domain OS method in synchronized spontaneous otoacoustic emission estimation, but not in the estimation of transient-evoked otoacoustic emission. Reasons for the performance discrepancy are discussed.

Acoustic differences in tinnitus between noise-induced and non-noise-induced hearing loss

Background Tinnitus, the perception of sound without external stimuli, varies across hearing loss types. The present study compared the acoustic characteristics of tinnitus in patients with noise-induced hearing loss (NIHL) and in those with hearing loss unrelated to noise exposure. Objective This study compared the acoustic characteristics of tinnitus in patients with noise-induced and non-noise-induced hearing loss. Methods A total of 403 patients with tinnitus were divided into those with noise-induced and non-noise-induced hearing loss. Patients were evaluated by pure tone audiometry (PTA), tinnitogram, transient evoked otoacoustic emission (TEOAE), distortion product otoacoustic emission (DPOAE), and auditory brainstem evoked response (ABR) tests. Results Patients with NIHL exhibited significantly higher hearing thresholds across all frequencies (125–8000 Hz) (p < .05) and reported significantly higher tinnitus intensity (p < .05). Otoacoustic emission tests showed that response rates were significantly lower (p < .05), and ABR tests found that latency periods were significantly more prolonged (p < .05), in patients with NIHL. Conclusions Tinnitus differs acoustically between patients with NIHL and those with non-noise-induced hearing loss, with specific patterns of intensity and auditory responses. These findings emphasize the need for tailoring the management of tinnitus according to the underlying type of hearing loss.

Normal linear and non-linear cochlear mechanisms and efferent system functioning in individuals with misophonia.

Misophonia, a condition characterized by heightened sensitivity and strong emotional reactions to specific sounds, has sparked considerable interest and debate regarding its underlying auditory mechanisms. The study aimed to understand the auditory underpinnings of two such potential inner ear systems, non-linear and linear outer hair cell functioning along with auditory efferent functioning in individuals with misophonia. 40 ears with misophonia (20 participants) and 37 ears without misophonia (20 participants), both having normal hearing sensitivity were included in this study. Transient evoked otoacoustic emissions (TEOAEs) and distortion product otoacoustic emissions (DPOAEs) were obtained in two conditions (with and without contralateral noise). Results of independent-samples t-test showed no statistically significant difference (p > 0.05) in the absolute amplitudes of both TEOAEs and DPOAEs between the individuals with and without misophonia. There was no statistically significant difference (p > 0.05) observed in the magnitude of suppression amplitude between the two groups for in both TEOAEs and DPOAEs between individuals with and without misophonia. These results suggest that the cochlear and efferent auditory underpinnings examined in this study may not be major contributors to the development or manifestation of misophonia.

Neonatal hearing screening - does failure in TEOAE screening matter when the AABR test is passed?

PurposeNewborns who fail the transient evoked otoacoustic emissions (TEOAE) but pass the automatic auditory brainstem response (AABR) in universal newborn hearing screening (UNHS), frequently have no further diagnostic test or follow-up. The present study aimed to investigate whether hearing loss might be missed by ignoring neonatal TEOAE failure in the presence of normal AABR.MethodsA retrospective analysis was conducted in newborns presenting between 2017 and 2021 to a tertiary referral centre due to failure in the initial UNHS. The main focus was on infants who failed TEOAE tests, but passed AABR screening. The clinical characteristics and audiometric outcomes were analysed and compared with those of other neonates.ResultsAmong 1,095 referred newborns, 253 (23%) failed TEOAE despite passing AABR screening. Of the 253 affected infants, 154 returned for follow-up. At 1-year follow-up, 46 (28%) achieved normal audiometric results. 32 (21%) infants had permanent hearing loss (HL) confirmed by diagnostic ABR, 58 (38%) infants had HL solely due to middle ear effusion (MEE), and for 18 (12%) infants HL was suspected without further differentiation. The majority of permanent HL was mild (78% mild vs. 13% moderate vs. 9% profound). The rate of spontaneous MEE clearance was rather low (29%) leading to early surgical intervention in 36 children. The profile of the risk factors for hearing impairment was similar to that of newborns with failure in both, TEOAE and AABR; however, there was a stronger association between the presence of risk factors and the incidence of HL (relative risk 1.55 vs. 1.06; odds ratio 3.61 vs. 1.80).ConclusionIn newborns, the discordance between a “refer” in TEOAE and a “pass” in AABR screening is associated with a substantial prevalence of hearing impairment at follow-up, especially in the presence of risk factors.

Hearing Loss and the Affecting Factors in Patients with Fibromyalgia.

To find the frequency of hearing loss in newly diagnosed patients with fibromyalgia (FM), and the factors affecting it. Descriptive study. Place and Duration of the Study: Department of Physical Medicine and Rehabilitation and Department of Otorhinolaryngology Head and Neck Surgery, Istanbul Medeniyet University, Goztepe Prof. Dr. Suleyman Yalcin City Hospital, Turkey, from March 2021 to November 2022. Patients with FM and gender/age matched controls were compared with pure-tone audiometric (PTA), and transient evoked otoacoustic emissions (TEOE) tests after standardised otorhinolaryngologic assessment The subjects were questioned for NSAID uptake and scored with ASAS-NSAID score. There were 33 patients with FM and 32 healthy volunteers. Subjective tinnitus, dizziness, and hearing loss rate in the FM group were 12%, 18%, and 15%, respectively. PTA air and bone conduction studies yielded significant differences between the control and FM group (p<0.05). The statistical difference was pronounced in higher frequencies. TEOE tests showed the FM group had significantly lower scores when compared to the control group at 3000 Hz and 4000 Hz (p<0.05). The median ASAS-NSAID scores were 0 for the control group and 7.78 for the FM group (p <0.001). Patients with FM had high rate of audiometric hearing loss of the sensorineural type. The abnormalities were more prominent in the high frequencies but also present in the low frequencies. Fibromyalgia syndrome, Hearing loss, Audiometry, Ototoxicity, Central sensitisation.

Otoacoustic emission measurements: a test–retest reliability study

ObjectivesOtoacoustic emissions (OAEs) are an important part of the audiological test battery and have many clinical uses. This study aims to determine the amplitude changes in the test–retest condition of distortion product otoacoustic emissions (DPOAEs) and transient-evoked otoacoustic emissions (TEOAEs), which are widely used in clinical settings.DesignDPOAE and TEOAE measurements were taken in 110 ears of 55 adults aged 18–35 years with normal hearing during three sessions. The repeatability of the measurements was evaluated by very short-term measurements taken 20 min after the first measurement and by short-term measurements taken 20 days after the first measurement.ResultsThere was no statistically significant difference between the three measurements in which DPOAE and TEOAE amplitudes were evaluated. The weakest reliability for TEOAEs was determined at frequencies of 1.0 kHz and 1.5 kHz, and the weakest reliability for DPOAEs was determined at 6728 Hz.ConclusionsThe current findings indicate that DPOAE and TEOAE measurements are reliable for monitoring cochlear function over time. The data obtained from this study could help clinicians correctly interpret OAE changes and distinguish between physiological and pathological changes.

Microcontroller-based acquisition system for evoked otoacoustic emissions: Protocol and methodology

This work presents the development of a signal acquisition and processing system for the fast detection of Transient-Evoked Otoacoustic Emissions (TEOAE). It was built under IEC 60645-6, IEC 62304, and IEC 82304-1 standards. Hardware and firmware specifications based on a Cortex-M7 microcontroller and an ER-10D acquisition probe are presented. A user interface was designed for parameter configuration and monitoring the detection process in a host personal computer. The signal processing chain is presented, and a time–frequency binary-mask approach is proposed to increase the signal-to-noise ratio, leading to a significant decrease in the average detection time. Results obtained with the implemented prototype for two different detection strategies were compared with those from a commercial equipment. Screening tests were performed with eight volunteers and one neonate with normal hearing. On average, the proposed hardware and associated signal processing methods provided a detection time fourteen times faster than the analyzed commercial system. These results are of special interest to developers of TEOAE screening systems.

Auditory function in humans at high altitude. A scoping review.

High-altitude (HA) affects sensory organ response, but its effects on the inner ear are not fully understood. The present scoping review aimed to collect the available evidence about HA effects on the inner ear with focus on auditory function. The scoping review was conducted following the guidelines of the Preferred Reporting Items for Systematic Review and Meta-Analysis extension for scoping reviews. PubMed, Scopus, and Web of Science electronic databases were systematically searched to identify studies conducted in the last 20 years, which quantified in healthy subjects the effects of HA on auditory function. The systematic search identified 17 studies on a total population of 888 subjects (88.7% male, age: 27.8 ± 4.1 years; median sample size of 15 subjects). Nine studies were conducted in a simulated environment and eight during real expeditions at HA. To quantify auditory function, six studies performed pure tone audiometry, four studies measured otoacoustic emissions (OAE) and eight studies measured auditory evoked responses (AER). Study protocols presented heterogeneity in the spatio-temporal patterns of HA exposure, with highly varying maximal altitudes and exposure durations. Most studies reported a reduction of auditory function with HA in terms of either elevation of auditory thresholds, lengthening of AER latencies, reduction of distortion-product and transient-evoked OAEs. Future studies in larger populations, using standardized protocols and multi-technique auditory function evaluation, are needed to further characterize the spatio-temporal pattern of HA effects along the auditory pathways and clarify the pathophysiological implications and reversibility of the observed changes.

The effect of coffee on contralateral suppression of transient evoked otoacoustic emissions.

Background: Coffee is a popular non-alcoholic beverage consumed by humans across the world. It contains caffeine, which is a type of stimulant of the central nervous system. In the auditory system, it has a positive effect on auditory brainstem response and perception of speech in noise. Further, caffeine has an inhibitory effect in the cochlea, but studies have rarely investigated its effect on otoacoustic emissions (OAEs) in humans. OAEs are low-intensity sounds produced by the cochlea, which could be recorded in the ear canal. The present study was carried out to investigate the effect of coffee on transient evoked otoacoustic emission (TEOAE) and contralateral suppression of TEOAE. Method: A total of 52 young adults participated in the study. A cross-over study design was used for the present investigation. The TEOAE and contralateral suppression of TEOAE were recorded before and after consumption of coffee and milk. The contralateral suppression of TEOAE was measured by presenting white noise to the contralateral ear at 40, 50, and 60 dB sound pressure level (SPL). Results: The mean amplitude of TEOAE before and after consumption of coffee was similar in both ears. Further, the mean contralateral suppression of TEOAE was slightly larger after consumption of coffee in both ears. However, the mean difference was not significant in both the ears. Conclusions: Based on the findings of present study, coffee has no significant effect on the amplitude of TEOAE and contralateral suppression of TEOAE.

Cochlear Function in Individuals with and without Spontaneous Otoacoustic Emissions.

This study investigated the status of spontaneous otoacoustic emissions (SOAEs) on cochlear function in a cohort of male/female participants with a wide age range. It examined whether there was a correlation between the presence of SOAEs and measurements of transient evoked otoacoustic emissions (TEOAEs), distortion product otoacoustic emissions (DPOAEs), SOAEs and extended high-frequency (EHF) hearing thresholds. 463 participants (222 male, 241 female; age range 20-59 years) with pure-tone thresholds ≤25 dB HL for octave frequencies of 500-8000 Hz were included in the study, divided into three age groups (20-29, 30-39, and 40-59 years). Evaluations included EHF (9000-16,000 Hz) hearing thresholds and TEOAE, DPOAE and SOAE measures. Multiple regression models showed that participants with SOAEs had larger expected amplitudes and signal-to-noise ratios (SNRs) for TEOAE and DPOAE responses than participants without SOAEs, holding gender and age variables constant. Spearman correlation tests identified deterioration in TEOAE and DPOAE amplitudes and SNRs, and EHF hearing thresholds with age in participants without SOAEs. Among participants with SOAEs, no significant decreases in TEOAE and DPOAE measures were shown in participants with older age. Nonetheless, as expected, EHF hearing thresholds did become worse with age, with or without SOAEs. Participants with identifiable SOAEs had greater TEOAE and DPOAE amplitudes and SNRs than participants without SOAEs. SOAEs appear to be a useful marker of cochlear health in adults.