Distortion Product Otoacoustic Emission Measurements Research Articles

Auditory Effects of Acoustic Noise From 3-T Brain MRI in Neonates With Hearing Protection.

Neonates with immature auditory function (eg, weak/absent middle ear muscle reflex) could conceivably be vulnerable to noise-induced hearing loss; however, it is unclear if neonates show evidence of hearing loss following MRI acoustic noise exposure. To explore the auditory effects of MRI acoustic noise in neonates. Prospective. Two independent cohorts of neonates (N = 19 and N = 18; mean gestational-age, 38.75 ± 2.18 and 39.01 ± 1.83 weeks). T1-weighted three-dimensional gradient-echo sequence, T2-weighted fast spin-echo sequence, single-shot echo-planar imaging-based diffusion-tensor imaging, single-shot echo-planar imaging-based diffusion-kurtosis imaging and T2-weighted fluid-attenuated inversion recovery sequence at 3.0 T. All neonates wore ear protection during scan protocols lasted ~40 minutes. Equivalent sound pressure levels (SPLs) were measured for both cohorts. In cohort1, left- and right-ear auditory brainstem response (ABR) was measured before (baseline) and after (follow-up) MRI, included assessment of ABR threshold, wave I, III and V latencies and interpeak interval to determine the functional status of auditory nerve and brainstem. In cohort2, baseline and follow-up left- and right-ear distortion product otoacoustic emission (DPOAE) amplitudes were assessed at 1.2 to 7.0 kHz to determine cochlear function. Wilcoxon signed-rank or paired t-tests with Bonferroni's correction were used to compare the differences between baseline and follow-up ABR and DPOAE measures. Equivalent SPLs ranged from 103.5 to 113.6 dBA. No significant differences between baseline and follow-up were detected in left- or right-ear ABR measures (P > 0.999, Bonferroni corrected) in cohort1, or in DPOAE levels at 1.2 to 7.0 kHz in cohort2 (all P > 0.999 Bonferroni corrected except for left-ear levels at 3.5 and 7.0 kHz with corrected P = 0.138 and P = 0.533). A single 40-minute 3-T MRI with equivalent SPLs of 103.5-113.6 dBA did not result in significant transient disruption of auditory function, as measured by ABR and DPOAE, in neonates with adequate hearing protection. 2. Stage 5.

Ototoxicity: a high risk to auditory function that needs to be monitored in drug development.

Hearing loss constitutes a major global health concern impacting approximately 1.5 billion people worldwide. Its incidence is undergoing a substantial surge with some projecting that by 2050, a quarter of the global population will experience varying degrees of hearing deficiency. Environmental factors such as aging, exposure to loud noise, and the intake of ototoxic medications are implicated in the onset of acquired hearing loss. Ototoxicity resulting in inner ear damage is a leading cause of acquired hearing loss worldwide. This could be minimized or avoided by early testing of hearing functions in the preclinical phase of drug development. While the assessment of ototoxicity is well defined for drug candidates in the hearing field - required for drugs that are administered by the otic route and expected to reach the middle or inner ear during clinical use - ototoxicity testing is not required for all other therapeutic areas. Unfortunately, this has resulted in more than 200 ototoxic marketed medications. The aim of this publication is to raise awareness of drug-induced ototoxicity and to formulate some recommendations based on available guidelines and own experience. Ototoxicity testing programs should be adapted to the type of therapy, its indication (targeting the ear or part of other medications classes being potentially ototoxic), and the number of assets to test. For multiple molecules and/or multiple doses, screening options are available: in vitro (otic cell assays), ex vivo (cochlear explant), and in vivo (in zebrafish). In assessing the ototoxicity of a candidate drug, it is good practice to compare its ototoxicity to that of a well-known control drug of a similar class. Screening assays provide a streamlined and rapid method to know whether a drug is generally safe for inner ear structures. Mammalian animal models provide a more detailed characterization of drug ototoxicity, with a possibility to localize and quantify the damage using functional, behavioral, and morphological read-outs. Complementary histological measures are routinely conducted notably to quantify hair cells loss with cochleogram. Ototoxicity studies can be performed in rodents (mice, rats), guinea pigs and large species. However, in undertaking, or at the very least attempting, all preclinical investigations within the same species, is crucial. This encompasses starting with pharmacokinetics and pharmacology efficacy studies and extending through to toxicity studies. In life read-outs include Auditory Brainstem Response (ABR) and Distortion Product OtoAcoustic Emissions (DPOAE) measurements that assess the activity and integrity of sensory cells and the auditory nerve, reflecting sensorineural hearing loss. Accurate, reproducible, and high throughput ABR measures are fundamental to the quality and success of these preclinical trials. As in humans, in vivo otoscopic evaluations are routinely carried out to observe the tympanic membrane and auditory canal. This is often done to detect signs of inflammation. The cochlea is a tonotopic structure. Hair cell responsiveness is position and frequency dependent, with hair cells located close to the cochlea apex transducing low frequencies and those at the base transducing high frequencies. The cochleogram aims to quantify hair cells all along the cochlea and consequently determine hair cell loss related to specific frequencies. This measure is then correlated with the ABR & DPOAE results. Ototoxicity assessments evaluate the impact of drug candidates on the auditory and vestibular systems, de-risk hearing loss and balance disorders, define a safe dose, and optimize therapeutic benefits. These types of studies can be initiated during early development of a therapeutic solution, with ABR and otoscopic evaluations. Depending on the mechanism of action of the compound, studies can include DPOAE and cochleogram. Later in the development, a GLP (Good Laboratory Practice) ototoxicity study may be required based on otic related route of administration, target, or known potential otic toxicity.

Combined genetic polymorphisms of the GSTT1 and NRF2 genes increase susceptibility to cisplatin-induced ototoxicity: A preliminary study

ObjectiveThe genotype-phenotype relationship in cisplatin-induced ototoxicity remains unclear. By assessing early shifts in distortion product otoacoustic emission (DPOAE) levels after initial cisplatin administration, we aimed to discriminate patients’ susceptibility to cisplatin-induced ototoxicity and elucidate their genetic background. Study DesignA prospective cross-sectional study. SettingTertiary referral hospital in Japan. PatientsTwenty-six patients with head and neck cancer were undergoing chemoradiotherapy with three cycles of 100 mg/m2 cisplatin. InterventionsRepetitive pure-tone audiometry and DPOAE measurements, and blood sampling for DNA extraction were performed. Patients were grouped into early ototoxicity presence or absence based on whether DPOAE level shifts exceeded the corresponding reference limits of the 21-day test interval. Main Outcome MeasuresHearing thresholds after each cisplatin cycle, severity of other adverse events, and polymorphisms in cisplatin-induced ototoxicity-associated genes were compared. ResultsEarly ototoxicity was present in 14 and absent in 12 patients. Ototoxicity presence on DPOAEs was associated with greater progression of hearing loss in frequencies ≥2 kHz throughout therapy and with higher ototoxicity grades compared with ototoxicity absence. Ototoxicity was further associated with grade ≥2 nausea. Ototoxicity presence was genetically associated with the GSTT1 null genotype and G-allele of NFE2L2 rs6721961, whereas ototoxicity absence was associated with the GSTM1 null genotype. Dose-dependent progression of hearing loss was the greatest in the combined genotype pattern of GSTT1 null and the T/G or G/G variants of rs6721961. ConclusionEarly DPOAE changes reflected genetic vulnerability to cisplatin-induced ototoxicity. Hereditary insufficiency of the antioxidant defense system causes severe cisplatin-induced hearing loss and nausea.

Physiological characterization of a macaque model of presbycusis

Age-related hearing loss (presbycusis) is the leading cause of hearing loss worldwide, but current human studies do not separate this pathology from lifetime noise exposure. Laboratory macaques live in environments with minimal noise-induced hearing trauma and have long lifespans, making them optimal presbycusis models. We describe age-related auditory changes using two clinical, non-invasive physiological measures in aging macaques: distortion product otoacoustic emissions (DPOAEs) and auditory brainstem responses (ABRs). ABRs and DPOAEs were measured in anesthetized young (6–9 years old, n = 36 ears) and aging (26–35 years old, n = 20 ears) Macaca mulatta. ABR and DPOAE thresholds were elevated in aging subjects compared to young macaques at all tested frequencies. ABR thresholds were significantly correlated with age for frequencies >8 kHz, but DPOAE thresholds were not, a pattern likely attributable to a high-frequency ceiling effect for DPOAE measures. For frequencies <8 kHz, DPOAE thresholds showed significant correlation with age. However, this was not observed with ABR thresholds, suggesting differential sensitivity to age-related changes for auditory nerve and brainstem function compared to cochlear outer hair cell function. Ongoing analysis on temporal processing/adaptation metrics will further elucidate age-related changes. Future work will correlate these findings with histological analysis. [Work Supported by NIH R01-DC-015988.]

Measurement of distortion-product otoacoustic emissions at low frequency and effect of contralateral acoustic stimulation on its level

Measurement of distortion-product otoacoustic emissions (DPOAEs) is one of the functional tests for the outer hear cells in the cochlea. Since the sound levels of the DPOAEs are quite low, it is easy to be buried in noise especially in the low frequency range, and frequency analysis and time averaging are required to detect them. In this study, focusing on the frequency stability of two stimulus sounds and a most prominent DPOAE-component, we tried to reduce noise floor and shorten the measurement time by choosing an adequate time window length for averaging the sound pressure waveform in the ear canal and the number of the averaging. As a result, it has become possible to measure DPOAEs at the low frequencies around 300 Hz in a relatively short time. Using this method, the changes in the DPOAE level induced by contralateral acoustic stimulation, which are caused by medial olivocochlear reflex, were measured. Although some exceptions were observed, the DPOAE was suppressed with increasing the sound pressure of the contralateral stimulus, and the degree of suppression was greater for the lower-frequency DPOAEs.

Otologic safety of intratympanic N-acetylcysteine in an animal model.

N-acetylcysteine (NAC) is an anti-oxidant and mucolytic effective against bacterial biofilms, making it useful in the treatment of chronically discharging ears that are unresponsive to traditional treatment methods. The objective of this study was to evaluate the otologic safety of intratympanic NAC combined with Ciprodex® in an animal model. Baseline distortion product otoacoustic emissions (DPOAE) and auditory brainstem response (ABR) measurements were performed for both ears on thirteen guinea pigs from the animal care research facilities of the McGill University Health Center. This was followed by intratympanic administration of control solution (Ciprofloxacin 0.3%/Dexamethasone 0.1%) to the left ear and experimental solution (1.25% NAC/Ciprofloxacin 0.3%/Dexamethasone 0.1%) to the right ear. Three additional intratympanic injections were performed over the next fourteen days. DPOAE and ABR measurements were repeated 3-4 weeks after the initial procedure. Outcome measures included differences in DPOAE and ABR thresholds after intervention, clinical evidence of vestibular dysfunction and histological evidence of ototoxicity. There were no significant differences in the ABR thresholds and DPOAE results of the control and experimental ears at baseline and after intervention. There was neither clinical manifestation of vestibular dysfunction nor histological evidence of ototoxicity. Our study suggests that intratympanic 1.25% NAC with ciprofloxacin and dexamethasone is safe in guinea pigs and support its potential use in the treatment of chronically discharging ears. Further studies in humans are required to analyze its efficacy relative to conventional treatments. Animal Research.

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.

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.

Effects of Cross-linked Hyaluronic Acid in a Rat Model of Vestibular and Cochlear Toxicity.

To investigate the effects of cross-linked hyaluronic acid (CLHA) in an experimental model of vestibulotoxicity and cochleotoxicity. Twenty-eight female Wistar albino rats (200-250 g) were divided into four groups. Group A received 0.06 mL of 13.33 mg/mL gentamicin, Group B received 0.06 mL of CLHA, Group C received 0.03 mL of 26.66 mg/mL gentamicin and 0.03 mL CLHA, and Group D received 0.06 mL of 0.09% saline. All groups underwent auditory brainstem response testing at 4-32 kHz, signal-to-noise ratio of distortion product otoacoustic emission measurements at 1.5-8 kHz and vestibular tests on days 0,1,7,10. The rats were sacrificed, and their labyrinths were histologically assessed and scored. The hearing thresholds of Groups A and C were similar and significantly higher than those of the other groups at all frequencies, beginning from day 1. The vestibular and histological scores of Groups A and C were similar and significantly higher than those of the other groups from day 1. The audiological results, vestibular scores, and histological scores of Groups B and D were similar, except for a temporary middle ear effusion and hearing threshold shift in Group B. No significant deterioration was observed in the audiological, vestibular, and histological analyses of Groups B and D. That both Group A and Group C similarly showed worsening audiological, vestibular, and histological tests suggests that CLHA did not alter the pharmacokinetics and histologic results of gentamicin.

Measurement of swept level distortion product otoacoustic emission growth functions at multiple frequencies simultaneously.

Otoacoustic emissions (OAEs) are low-level sounds generated by the inner ear that provide a non-invasive assessment of cochlear health. Advanced applications require recording OAEs across a wide range of frequencies and stimulus levels. Detailed here is a method for efficiently measuring distortion product otoacoustic emissions (DPOAEs) across an expansive stimulus space. Specifically, DPOAEs are recorded by sweeping the evoking stimuli in level across multiple frequencies simultaneously. This method generates DPOAE growth functions at multiple f2 frequencies in several minutes. Results indicate the swept level method yields DPOAEs equivalent to those measured in a traditional (discrete stimulus) paradigm, but with several advantages.

Changes in the cochlear and retrocochlear parts of the auditory system in 19-39 and 40-60 years old patients with type 1 diabetes mellitus.

Pathophysiological alterations in the cochlea and functional tests of the auditory pathway support that in diabetes both vasculopathy and neural changes could be present. The aim of our research was to study the differential effect of type 1 diabetes mellitus (T1DM) on two different age groups. Audiological investigation was carried out in 42 patients and 25 controls at the same age groups. Investigation of the conductive and sensorineural part of the hearing system by pure tone audiometry, distortion product otoacoustic emission measurement and acoustically evoked brainstem response registration were evaluated. Among the 19-39-year-old people the incidence of hearing impairment was not different in the diabetes and control groups. Among the 40-60-year-old people hearing impairment was more common in the diabetes group (75%) than in the control group (15,4%). Among patients with type 1 diabetes, the mean threshold values were higher in both age groups at all frequencies although significant difference was in 19-39 years old group: 500-4000Hz right ear, 4000Hz left ear, in 40-60 years old group: 4000-8000 Hz both ears. In the 19-39 years old diabetes group only at 8000 Hertz on the left side was a significant (p<0,05) difference in otoacoustic emissions. In the 40-60 years old diabetes group significantly less otoacoustic emissions at 8000 Hz on the right side (p<0,01) and at 4000-6000-8000 Hertz on the left side, (p<0,05, p<0,01, p<0,05 respectively) was present compared to the control group. According to ABR (auditory brainstem response) latencies and wave morphologies, a possible retrocochlear lesion arose in 15% of the 19-39 years old and 25% of the 40-60 years old diabetes group. According to our results, T1DM affects negatively the cochlear function and the neural part of the hearing system. The alterations are more and more detectable with aging.

Tetramethylpyrazine Attenuates Radiation-Induced Ototoxicity in a Rat Model

Introduction: Tetramethylpyrazine (TMP) is a chemical compound, which has been shown to possess numerous biological features such as anticoagulation, inhibition of platelet aggregation, anti-inflammation, capillary dilatation, improvement in microcirculation, and protection against reactive oxygen radicals. The aim of the present study was to investigate the protective effect of TMP against radiation-induced ototoxicity. Materials and Methods: 40 rats were divided into four groups. The first group was irradiated for 5 days. The second group received a single dose of 140 mg/kg/day intraperitoneal TMP given to the rats 30 min before radiotherapy (RT) for 5 days. The third group received a single dose of 140 mg/kg/day i.p. TMP for 5 days, whereas the fourth group was administered saline. All rats underwent distortion product otoacoustic emission (DPOAE) and auditory brainstem response measurements before and after the application. The temporal bulla of animals was removed for immunohistopathological examination. Results: Signal-noise ratio values were significantly decreased in the RT group for the frequencies of 2–32 kHz after RT (p < 0.05), whereas the difference was not significant in terms of pre- and posttreatment values for the other groups. Also in the RT group, the ABR thresholds were significantly increased after treatment. In H&E staining, the mean scores for outer hair cells (OHCs), stria vascularis (SV), and spiral ganglion (SG) injuries were significantly higher in RT and RT + TMP groups than in the other groups. The mean OHCs and SV injury scores were also significantly higher in the RT group than in the RT + TMP group (p < 0.05). The number of cochleas that showed cytoplasmic caspase-3 immunoreactivity in the OHC, SV, and SG was significantly higher in RT and RT + TMP groups than in the other groups. Conclusion: The findings of the present study suggest that TMP may have a therapeutic potential for preventing sensorineural hearing loss (SNHL) related to RT.

Curcumin attenuates gentamicin and sodium salicylate ototoxic effects by modulating the nuclear factor-kappaB and apoptotic pathways in rats

This study aimed to investigate the effectiveness of curcumin (CCM) against gentamicin (GEN) and sodium salicylates (NaS)-induced ototoxic effects in rats. For 15 consecutive days, seven rat groups were given 1 mL/rat physiological saline orally, 1 mL/rat olive oil orally, 50 mg/kg bwt CCM orally, 120 mg/kg bwt GEN intraperitoneally, 300 mg/kg bwt NaS intraperitoneally, CCM+GEN, or CCM+NaS. The distortion product otoacoustic emission measurements were conducted. The rats’ hearing function and balance have been behaviorally assessed using auditory startle response, Preyer reflex, and beam balance scale tests. The serum lipid peroxidation and oxidative stress biomarkers have been measured. Immunohistochemical investigations of the apoptotic marker caspase-3 and the inflammatory indicator nuclear factor kappa (NF-κB) in cochlear tissues were conducted. GEN and NaS exposure resulted in deficit hearing and impaired ability to retain balance. GEN and NaS exposure significantly decreased the reduced glutathione level and catalase activity but increased malondialdehyde content. GEN and NaS exposure evoked pathological alterations in cochlear and vestibular tissues and increased caspase-3 and NF-κB immunoexpression. CCM significantly counteracted the GEN and NaS injurious effects. These outcomes concluded that CCM could be a naturally efficient therapeutic agent against GEN and NaS-associated ototoxic side effects.Graphical abstract

A Correlational Analysis between Audiometric Pure-tone Averages and Distortion Product Otoacoustic Emissions.

Hearing loss severely affects human speech communication and the quality of life, and efficient hearing screening can help hearing function diagnosis and subsequent hearing rehabilitation. Pure-tone audiometry test and distortion-product otoacoustic emission (DPOAE) measurement are two commonly-used clinical techniques for hearing loss diagnosis, and they were developed based on different mechanisms in a hearing process. Early work investigated the relation between audiometric thresholds and DPOAE measurements. The present work aimed to use a simple linear fitting to estimate audiometric pure-tone threshold averages (PTAs) from DPOAE signal-to-noise-ratio (SNR) measurements, i.e., DPOAE amplitude minus the mean noise floor. Audiometric PTA values and DPOAE SNRs were measured from both ears of 30 listeners with normal hearing or mild-to-moderate hearing loss. The DPOAE SNR measurements of 4 distortion products (i.e., 2fl-f2= 1, 2, 4 and 8 kHz) were combined with a linear prediction model, and correlated with the PTA values. Data analysis showed moderate high correlation coefficients (i.e., r=0.84 and 0.64) for the left and right ears, respectively. The results of the present work demonstrate the possibility to estimate the behavioral audiometric PTA values from the objective DPOAE SNR measurements for hearing loss diagnosis.

Comparison of otoacoustic emissions in tinnitus and hyperacusis in adults with normal hearing sensitivity

Objective To investigate the effect of tinnitus and/or hyperacusis on distortion product otoacoustic emission (DPOAE) measures in adults with normal hearing thresholds from 0.25 to 8 kHz, while accounting for extended high-frequency (EHF) thresholds. Design A behavioural study consisted of comprehensive audiological assessment, validated tinnitus and hyperacusis questionnaires, DPOAE amplitudes and input/output (I/O) functions. Study sample Data of 56 participants with normal hearing were included for the analysis. Participants were categorised into four groups: (1) without tinnitus or hyperacusis, (2) with tinnitus only, (3) with hyperacusis only, and (4) with both tinnitus and hyperacusis. Results The groups with tinnitus showed elevated EHF thresholds compared with those without tinnitus. DPOAE amplitudes were not significantly affected by tinnitus and/or hyperacusis status; however, they were significantly affected by EHF thresholds. Further, no appreciable differences in DPOAE I/O functions were found across groups. Conclusions The reported non-significant differences in DPOAEs in individuals with tinnitus and/or hyperacusis do not support a peripheral mechanism or an interaction between peripheral and central mechanisms underlying tinnitus or hyperacusis. Our findings, however, suggest the need to assess basal cochlear function (e.g. EHF thresholds) for a better understanding of differences in DPOAE measures in tinnitus and/or hyperacusis.

Binaural brainstem and spatial hearing deficits in a guinea pig model of noise-Induced cochlear synaptopathy

Animal studies have revealed that moderate-level noise exposure can cause a permanent loss of ribbon synapses between inner hair cells and auditory-nerve fibers, but only temporary threshold shifts. Such noise-induced cochlear synaptopathy has been called ‘hidden hearing loss’ because while there is a significant degeneration of ribbon synapses, the resulting hearing dysfunction is effectively hidden from typical clinical assays. Here we used guinea pigs to study the mechanisms leading to hearing deficits resulting from a moderate noise. We measured distortion product otoacoustic emissions and auditory brainstem responses to assay peripheral hearing. We tested spatial hearing ability through the prepulse inhibition (PPI) of the acoustic startle reflex. PPI was used to measure hearing-in-noise ability, or spatial release from masking, as this task approximates the “cocktail party” effect. Finally, we performed immunohistochemistry to confirm synaptopathy. Results show that the noise exposure induces no permanent hearing threshold shift, but despite recovery of normal audibility, both behavioral and electrophysiological binaural hearing deficits persisted. Cochlear synaptopathy was objectively confirmed by visualizing the loss of ribbon synapses in the cochlea. The results demonstrate that cochlear synaptopathy causes deficits in brainstem circuits known to be critical for binaural and spatial hearing. [Work supported by Otolaryngology T32 DC012280.]

The influence of self-reported noise exposure on 2ƒ1-ƒ2 distortion product otoacoustic emission level, fine structure, and components in a normal-hearing population.

Distortion product otoacoustic emissions (DPOAEs) offer an outcome measure to consider for clinical detection and monitoring outer hair cell dysfunction as a result of noise exposure. This investigation detailed DPOAE characteristics and behavioral hearing thresholds up to 20 kHz to identify promising metrics for early detection of cochlear dysfunction. In a sample of normal-hearing individuals with and without self-reported noise exposure, the DPOAE and hearing threshold measures, as assessed by two questions, were examined. The effects on various auditory measures in individuals aged 10-65 years old with clinically normal/near-normal hearing through 4 kHz were evaluated. Individuals reporting occupational noise exposures (n = 84) and recreational noise exposures (n = 46) were compared to age-matched nonexposed individuals. The hearing thresholds and DPOAE level, fine structure, and component characteristics for the full frequency bandwidth were examined. The data suggest that the DPOAE levels measured using a range of stimulus levels hold clinical utility while fine structure characteristics offer limited use. Under carefully calibrated conditions, the extension to frequencies beyond 8 kHz in combination with various stimulus levels holds clinical utility. Moreover, this work supports the potential utility of the distortion product place component level for revealing differences in cochlear function due to self-reported, casual noise exposure that are not observable in behavioral hearing thresholds.

Ratlarda takrolimusun iç kulak üzerindeki etkisi

Purpose: Tacrolimus, an immunosuppressive agent, is used especially after organ transplantation. It has been asserted that tacrolimus has protective effects on the auditory system in some studies while it has negative effects in other studies. The purpose of our study is to investigate the effect of tacrolimus on the inner ear of the rats. &#x0D; Materials and Methods: 20 healthy Sprague Downey male rats weighing 250-350 grams were included in our study. The first group of rats were given 1mg/kg tacrolimus (n:7), the second group of rats were given 0.1 mg/kg tacrolimus (n:7), and the third group (n:6) was the non-administered control group. The first measurements of all rats were taken with distortion-product otoacoustic emission before starting the experiment. Then, tacrolimus drug was administered by gavage method to the 1st and 2nd groups along 30 days. The last measurement was repeated on the 30th day.&#x0D; Results: According to the results of the first measurements, emission was obtained in all rats and the responses were found to have similar characteristics. Similarly, the difference between the signal noise rate values in the last measurements taken from the groups did not show any statistical significance.&#x0D; Conclusions: Based on the distortion-product otoacoustic emission measurements, it can be said that Tacrolimus does not have ototoxic effects on the auditory system of rats considering the administered dosage and time.

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

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

Assessment of cochlear functions in hospitalized patients with SARS-CoV-2 infection

SARS-CoV-2 infection intensely increases thromboembolic events and inflammation. The inner ear can be easily damaged as a result of circulatory disorders and inflammation. Therefore, SARS-CoV-2 may negatively affect the cochlea. Outer hairy cell damage in the inner ear is one of the first signs of sensorineural hearing loss. Otoacoustic emissions use is an effective, objective, and non-invasive method for early detection of hearing loss. Our study aims to determine whether the cochlea is affected in hospitalized patients with SARS-CoV-2 infection who did not need intensive care treatment by using Distortion product otoacoustic emission (DPOAE) measurements. This study was conducted on 26 hospitalized patients with SARS-CoV-2 infection (patient group) and 25 healthy volunteers (control group). DPOAE measurements were performed on all participants in an audiometric test room. The DP-grams were obtained between 498Hz and 10000Hz. The DPOAE measurements were compared between two groups. When evaluated as a cluster, DP1 and the SNR values were found to be significantly lower in the patient group at frequencies 498, 996, 2002, 7998, 10000 Hz and frequencies 498, 996, 2002, 4004, 6299Hz, respectively. When the right and left ears of the patient group were compared, DP1 and SNR values were found to be similar at all frequencies. SARS-CoV-2 infection can cause damage to the outer hair cells and the regions of the cochlea belonging to a wide range of frequencies according to our DPOAE measurements and due to the specific characteristics of the virus.