Otoacoustic Emission Measurements Research Articles

Hearing Evaluations in Children With Retinoblastoma Treated With Intra-arterial Carboplatin Chemotherapy: A Single Institution Review.

To determine whether the administration of intra-arterial carboplatin affected the hearing of children with retinoblastoma. Children with retinoblastoma who were treated with intra-arterial carboplatin chemotherapy were included. Hearing tests before chemotherapy including tympanometry, distortion product otoacoustic emissions, and audiogram (if achievable) were performed and repeated 3 to 9 months after concluding intra-arterial therapy. The study was approved by the institutional review board. Patients were identified from the retinoblastoma clinic when the treatment plan included intra-arterial carboplatin chemotherapy. Children were excluded if they had previous intra-arterial carboplatin or preexisting hearing loss but were included if they had systemic carboplatin and dosing was available. Tympanometry was performed to rule out inner ear fluid. All examinations were performed by a certified audiologist with the same equipment, calibrated regularly by a certified technician. Twenty-two children (32 eyes) were evaluable. Because most children are diagnosed at a young age and are unable to participate in an audiogram, distortion product otoacoustic emission measurement was the primary measurement. No child displayed hearing loss. Intra-arterial chemotherapy with carboplatin did not cause ototoxicity in any child by distortion product otoacoustic emission measurement in contrast to systemic chemotherapy where ototoxicity is common. Distortion product otoacoustic emission levels were essentially unchanged from before to after intra-arterial chemotherapy in children with retinoblastoma. These findings suggest that intra-arterial carboplatin does not affect outer hair cell function, and distortion product otoacoustic emission tests can provide useful information when monitoring children at risk of developing carboplatin ototoxicity. [J Pediatr Ophthalmol Strabismus. 20XX;X(X):XXX-XXX.].

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.

Comparison of Two Clinical Devices for the Measurement of Distortion Product Otoacoustic Emissions in Normal-Hearing Adults.

Otoacoustic emissions (OAEs) are low-intensity sounds generated by the cochlea and associated with the function of the outer hair cells. Since OAE measurements do not require active participation of a listener, OAEs are considered an objective measure of cochlear function. While distortion-product OAEs (DPOAEs) are commonly used in clinical practice, limited information is available on the performance of various clinical devices. This study compared two commercial clinical devices, Titan and Eclipse from Interacoustics, and collected normative data for DPOAEs in people with normal hearing. The data collection and analysis were focused on signal and noise amplitudes as well as signal-to-noise ratios (SNRs). Sixty-three participants with normal hearing (age 23.2±2.0 years) were included in the study. DPOAEs were measured at 31 frequencies ranging from 500 to 10,000 Hz. DPOAE amplitude differed across frequencies. Additionally, a high number of unreliable responses were observed at the edge frequencies (<828 Hz and >6,072 Hz). There were no significant differences between the two devices in terms of DPOAE amplitudes, but the recorded-noise levels (amplitude) differed significantly. SNRs of the recorded OAEs were frequency dependent (higher frequencies showed larger SNRs), and significant differences in terms of SNR were found between the two devices. Despite the above-mentioned differences, the OAEs recorded with both devices met the pass criteria for the SNR (≥6 dB) consistently across frequencies, and thus the differences do not compromise the test outcomes. The frequency dependence of the OAE amplitudes and the corresponding SNRs may be relevant for clinical practice.

Does in vitro fertilization affect the hearing levels of women?

This study aimed to determine whether there is a relationship between changes in blood estrogen levels and hearing threshold levels in women undergoing in vitro fertilization (IVF). Sixty patients with normal otoscopic examination findings and scheduled for IVF treatment were included in the study. All patients underwent pure tone audiometry, tympanogram tests, and otoacoustic emission measurements (TEOAE) during IVF treatment, and estrogen levels were measured simultaneously. The patients were divided into three groups based on estrogen levels during IVF. The patients' audiological test results at the beginning and end of treatment (the 12th day) were compared between the groups. There was an increase in hearing levels on the 12th day of treatment compared to the beginning of treatment in all the study groups. This increase was significant between Group 1 and Group 2 and between Group 1 and Group 3 (p<0.05). The best hearing in audiometry was determined in the patients in Group 2. While a significant increase was observed in TEOAE (otoacoustic emission) measurements in Groups 1 and 2, a significant decrease was determined in Group 3 (p<0.05). Middle ear pressure and compliance measurements on the tympanogram tests were significantly lower in Group 3 compared to Groups 1 and 2 (p<0.05). During IVF treatment, as the estrogen level increases, it causes an increase in the level of hearing, but this increase does not continue after specific doses.

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.

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.

Assessing Auditory and Cochlear Function in Alopecia Areata Patients: Exploring the Link to Cochlear Melanocyte Damage.

Introduction Alopecia areata (AA) is an autoimmune disorder causing hair loss, including eyebrows, eyelashes, and body hair, primarily due to melanocyte impact. Though the precise AA melanocyte hearing loss mechanisms are not fully clear, it's speculated that cochlear melanocyte inflammation could disrupt endolymph production, which is necessary for sound signal transmission. Cochlear melanocytes maintain crucial potassium ion levels, which are pivotal for hearing. The potential AA-melanocyte-hearing loss link underscores the need to monitor auditory and cochlear function and consider interventions for AA-related hearing challenges. The study aimed to assess auditory and cochlear function using OAE and audiometry measurements to correlate disease severity and duration with OAE outcomes. Materials and methods In this study, we included 32 patients diagnosed with AA; the control group consisted of 29 healthy volunteers. We collected data on the patient's age, gender, onset age, family history, and disease duration. Audiological and otological evaluations were conducted, including pure tone audiometry (PTA), speech discrimination test (SD), and otoacoustic emission (DPOAE) measurements at frequencies of 500, 1000, 2000, 4000, 6000, 8000, and 10000 Hz. The patients were divided into two groups based on age: 18-25 and over 25 years old, and all parameters were compared. To examine differences between the right and left ears, gender, and age groups, we initially tested the variables for normal distribution using the Kolmogorov-Smirnov and Shapiro-Wilk tests. An independent sample t-test was conducted to compare the means for normally distributed variables. Results There were statistical differences at the 5% significance level in the mean DPOAE values of the 1 KHz SNR and 6 KHz SNR variables. According to the Mann-Whitney U test results, a significant difference was found in the gender-based DPOAE value at 2 kHz SNR (p=0.041), which was lower in men than women. Although there were no significant differences in the audiological parameters based on age, significant differences were found in the otoacoustic emission values. Variables, including 4 kHz DP1 (p=0.049), 500 Hz SNR (p=0.045), and 1 kHz SNR (p=0.023), differed significantly between age groups, with these values being lower in patients over 25 years old. Conclusion Overall, our study contributes to the growing body of evidence supporting an association between AA and auditory dysfunction, emphasizing the need for comprehensive assessment and management of hearing-related issues in individuals with AA.

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.

The Influence of a Single Therapeutic Dose of Methadone on Selected Auditory Functions in Patients Addicted to Opioids and Undergoing Substitution Therapy – a Preliminary Study

The main purpose of this research was to determine the influence of a therapeutic dose of an opioid drug (methadone) on selected auditory functions in patients addicted to opioids (recognition ICD-10; F11) and undergoing substitution therapy. Various hearing tests were used in this research – pure tone audiometry, impedance audiometry, otoacoustic emission measurement, and a speech in noise test – in two sessions, before and after methadone intake. It was found that methadone causes an improvement in speech intelligibility when speech is presented in speech-like noise, and slightly decreases hearing thresholds [dB HL]. Methadone consumption has no significant impact on distortion product otoacoustic emissions levels (DPOAE). In summary, a prescribed methadone dose does not worsen the hearing of opioid-dependent subjects.

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.

ABO blood group and cochlear function: evidence from a large sample size study

Objective The present study investigated the effect of blood group on cochlear function in a large participant sample across different age groups. The study hypothesis was that participants with blood group O would show relatively reduced cochlear function as reflected in otoacoustic emission (OAE) measures. Design Data were collected from transient evoked otoacoustic emission (TEOAE), distortion product otoacoustic emission (DPOAE), DPOAE input/output (I/O) function, and spontaneous otoacoustic emission (SOAE) recordings. Study sample Four hundred and sixty-three normal hearing adults aged 20–59 years among the four ABO blood groups participated in the study. Results TEOAE and DPOAE amplitudes did not reveal significant differences for participants with blood group O compared with participants with non-O blood groups. No significant differences in I/O function categories were found among participants with different blood groups. SOAE prevalence was also not significantly different across blood groups. However, previously reported age and gender differences for OAE variables were confirmed. Conclusions Participants with blood group O were not found to have significantly reduced cochlear function, based on OAE measures. Results from the current study do not support the hypothesis that normal hearing individuals with different ABO blood groups differ in level of cochlear function.

Noise-Induced Hearing Loss.

Noise-induced hearing loss (NIHL) is the second most common cause of sensorineural hearing loss, after age-related hearing loss, and affects approximately 5% of the world's population. NIHL is associated with substantial physical, mental, social, and economic impacts at the patient and societal levels. Stress and social isolation in patients' workplace and personal lives contribute to quality-of-life decrements which may often go undetected. The pathophysiology of NIHL is multifactorial and complex, encompassing genetic and environmental factors with substantial occupational contributions. The diagnosis and screening of NIHL are conducted by reviewing a patient's history of noise exposure, audiograms, speech-in-noise test results, and measurements of distortion product otoacoustic emissions and auditory brainstem response. Essential aspects of decreasing the burden of NIHL are prevention and early detection, such as implementation of educational and screening programs in routine primary care and specialty clinics. Additionally, current research on the pharmacological treatment of NIHL includes anti-inflammatory, antioxidant, anti-excitatory, and anti-apoptotic agents. Although there have been substantial advances in understanding the pathophysiology of NIHL, there remain low levels of evidence for effective pharmacotherapeutic interventions. Future directions should include personalized prevention and targeted treatment strategies based on a holistic view of an individual's occupation, genetics, and pathology.

A funkcionális halláscsökkenés felismerése és komplex diagnosztikája

Hearing loss is a sensory impairment that impairs speech understanding, communication and therefore the quality of life. Sometimes the patient's perceived loss of function is exaggerated; subjective and objective test results are inconsistent, the subjectively reported hearing loss is more significant, and in these cases functional hearing loss is considered. Our aim was to collect and retrospectively analyze cases with the diagnosis of functional hearing loss, in order to draw conclusions about the characteristics of functional hearing loss, the signs and conditions that may be of attention and the consideration of appropriate rehabilitation. Subjective tests were performed with pure-tone auditory threshold, speech understanding and communication tests, which were compared with the results obtained with objective impedance measurements, stapedial reflex tests, otoacoustic emission measurements, and brainstem evoked response recordings. Imaging studies, psychologist, psychiatrist, neurologist, neurologist and other co-specialists were involved as needed. We excluded cases of deception deliberately intended to obtain financial or other benefits. Between 2007 and 2022, 19 patients were diagnosed with functional hearing loss. The majority (17 cases) were female, the complaints were prevalent at a young age (10-41 years); the average age in the study population was 19.6 years, and the majority of patients (13 cases) were children aged 10-17 years. No organic cause was found in 11 cases, and in the remaining cases no detectable organic abnormality explained the extent of the hearing loss experienced by the patient. The degree of functional hearing loss varied (35-120 dB), with an average of 60,2 dB. Recognizing and diagnosing functional hearing loss is very difficult and requires a complex series of tests and professional cooperation. Without recognition, the patient may receive unjustified, even harmful and financially burdensome care, which may lead to the deterioration of his condition. Orv Hetil. 2023; 164(8): 283-292.

Metabolic and Sensory Components of Age-Related Hearing Loss: Associations With Distortion- and Reflection-Based Otoacoustic Emissions.

Age-related hearing loss is difficult to study in humans because multiple genetic and environmental risk factors may contribute to pathology and cochlear function declines in older adults. These pathologies, including degeneration of the stria vascularis, are hypothesized to affect outer hair cells responsible for active cochlear amplification of low-level sounds. Otoacoustic emission (OAE) measures are used to quantify the energy added to the traveling wave in cochlear amplification, which typically weakens with increased pure-tone thresholds and for older individuals. Thus, the current study evaluated two OAE measures for individuals with different components of age-related hearing loss. We examined two retrospective adult lifespan datasets (18 to 89+ years of age) from independent sites (Medical University of South Carolina and Boys Town National Research Hospital), which included demographics, noise history questionnaires, distortion-product otoacoustic emissions (DPOAE), and cochlear reflectance (CR). Metabolic and sensory estimates of age-related hearing loss were derived from the audiograms in each dataset, and then tested for associations with DPOAE and CR. The results showed that metabolic estimates increased for older participants and were associated with lower overall DPOAE and CR magnitudes across frequency (i.e., lower fitted intercepts). Sensory estimates were significantly higher for males, who reported more positive noise histories compared to females and were associated with steeper negative across-frequency slopes for DPOAEs. Although significant associations were observed between OAE configurations, DPOAEs appeared uniquely sensitive to metabolic estimates. The current findings suggest that distortion-based measures may provide greater sensitivity than reflection-based measures to the components of age-related hearing loss.

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.

Ototoxicity of Triclosan: A Rat Model Study.

Triclosan is utilized as an antibacterial factor in many industrial products. Although there are many toxic features of triclosan in the literature, there is no study on the effect of triclosan on hearing. The purpose of this study is to determine the effect of triclosan on hearing in rats. In this prospective, experimental animal study, 40 healthy Sprague-Dawley rats with normal response to the distortion-product otoacoustic emission (DPOAE) measurements were divided into four groups. Group 1, as the control group, was given only corn oil, group 2 was given 5 mg/kg triclosan dissolved in corn oil, group 3 was given 10 mg/kg triclosan dissolved in corn oil, and group 4 was given 100 mg/kg triclosan dissolved in corn oil; triclosan and corn oil were administered by oral gavage to all groups. In our study, low-dose triclosan did not cause hearing loss, but hearing loss was observed in the group that was given high-dose triclosan (100 mg/kg). These findings suggest that triclosan causes hearing loss in rats. This issue should be investigated further to avoid triclosan ototoxicity in humans.

Medial olivocochlear reflex strength in ears with low-to-moderate annual noise exposure

Recent work suggests enhanced medial-olivocochlear reflex (MOCR) strength in noise exposed individuals. The current study aimed to replicate this finding using stricter signal-to-noise ratio (SNR) criteria in MOCR estimates and a larger subject population. Ninety-eight normal-hearing young adults participated. The MOCR test included measurement of click-evoked otoacoustic emissions (CEOAE) with and without contralateral noise. MOCR-induced magnitude and phase shifts were calculated. The MOCR test was performed twice to provide a within-session replication. Annual noise exposure history was estimated using the Noise Exposure Questionnaire. Annual noise exposure was not a statistically significant predictor of the MOCR-induced CEOAE magnitude shift. A statistically significant negative correlation was found between annual noise exposure and the MOCR-induced CEOAE phase shift. A significant negative correlation was also identified between annual noise exposure and CEOAE level. Results suggest diminished MOCR strength in noise-exposed individuals. This finding contrasts with recent work using similar methods. Compared to earlier work, the current study relied on higher OAE SNRs in MOCR estimates and sampled a larger population of subjects with broader noise exposure histories. The concurrent finding of reduced OAE levels in noise exposed individuals suggests acoustic trauma may be an underlying cause of reduced MOCR strength.

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.