Assessment of Peripheral and Central Auditory Processing after Treatment for Idiopathic Sudden Sensorineural Hearing Loss.

Introduction When cases of idiopathic sudden sensorineural hearing loss (SSNHL) are treated successfully, most clinicians assume the normality and symmetry of the auditory processing. This assumption is based on the recovery of the detection ability on the part of the patients, but the auditory processing involves much more than detection alone. Since certain studies have suggested a possible involvement of the central auditory system during the acute phase of sudden hearing loss, the present study hypothesized that auditory processing would be asymmetric in people who have experienced sudden hearing loss. Objective To assess the physiologic and electrophysiological conditions of the cochlea and central auditory system, as well as behavioral discrimination, of three primary aspects of sound (intensity, frequency, and time) in subjects with normal ears and ears treated successfully for SSNHL. Methods The study included 19 SSNHL patients whose normal and treated ears were assessed for otoacoustic emissions, speech auditory brainstem response, intensity and pitch discrimination, and temporal resolution in a within-subject design. Results The otoacoustic emissions were poorer in the treated ears compared to the normal ears. Ear- and sex-dependent differences were observed regarding otoacoustic emissions and pitch discrimination. Conclusion The asymmetrical processing observed in the present study was not consistent with the hearing threshold values, which might suggest that the central auditory system would be affected regardless of the status of the peripheral hearing. Further experiments with larger samples, different recovery scenarios after treatment, and other assessments are required.

Conditions Underlying the Appearance of Spontaneous Otoacoustic Emissions in Mammals.

Across the wide range of land vertebrate species, spontaneous otoacoustic emissions (SOAE) are common, but not always found. The reasons for the differences between species of the various groups in their emission patterns are often not well understood, particularly within mammals. This review examines the question as to what determines in mammals whether SOAE are emitted or not, and suggests that the coupling between hair-cell regions diminishes when the space constant of frequency distribution becomes larger. The reduced coupling is assumed to result in a greater likelihood of SOAE being emitted.

The effect of tympanostomy tubes on otoacoustic emissions.

PURPOSE: Otoacoustic emissions (OAE) are a common screening tool to evaluate cochlear function. Middle ear dysfunction has been shown to impact results of otoacoustic emission testing, but there are limited data on the effect of tympanostomy tubes on OAE. The purpose of this study was to determine whether tympanostomy tube placement significantly improved OAE. METHODS: A retrospective review of charts was completed for patients younger than 18 years old who underwent tympanostomy tube placement from January 1, 2018 to September 1, 2023 and had preoperative and postoperative OAE testing within 6 months of surgery. The primary variable was presence of OAE preoperatively and postoperatively. Chi-square analysis and t test were used for statistical analysis. RESULTS: A total of 212 ears were examined from 111 pediatric patients who underwent tympanostomy tube placement during the study period. Presence of OAE at 3000, 4000, and 5000 Hz were all noted to significantly increase following tympanostomy tube placement, with OAE presence increasing from approximately 27.8% of the sample preoperatively to 95.3% postoperatively at 3000 and 4000 Hz. Patients who noted improvement had a significantly higher proportion of type B tympanogram preoperatively, compared to a higher proportion of type A tympanogram noted in patients who did not note improvement. CONCLUSION: Tympanostomy tubes can significantly improve otoacoustic emissions in patients with middle ear dysfunction.

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

BACKGROUND: 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. PURPOSE: To explore the auditory effects of MRI acoustic noise in neonates. STUDY TYPE: Prospective. SUBJECTS: Two independent cohorts of neonates (N = 19 and N = 18; mean gestational-age, 38.75 ± 2.18 and 39.01 ± 1.83 weeks). FIELD STRENGTH/SEQUENCE: 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. ASSESSMENT: 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. STATISTICAL TEST: 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. RESULTS: 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). DATA CONCLUSION: 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. EVIDENCE LEVEL: 2. TECHNICAL EFFICACY: Stage 5.

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

BACKGROUND AND OBJECTIVES: 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). SUBJECTS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Results of the Study of the Auditory Analyzer in Newborns with Hyperbilirubinemia.

According to statistics, hyperbilirubinemia is observed during the first week of life in approximately 60% of full-term and 80% of premature newborns. It is known that indirect bilirubin has a neurotoxic effect. Accumulation of unconjugated bilirubin in some brain structures may appear to be a temporary or unexpected impairment in auditory, motor, or cognitive function. The narrowing of the OAE spectrum and low amplitude of the response, the increase in the latent periods of III, IV, V peaks, as well as the prolongation of the time of the central sound conduction of the III-V and I-V waves in all newborns with hyperilirubinemia, indicates a pathology of hearing of central origin with impaired conduction along the auditory pathways at the level the lower and middle thirds of the pons of the brain (Р ≤ 0.05).

Exploring the origins of decreased sound tolerance in tinnitus patients.

This study aimed to confirm the characteristics of auditory function alterations in tinnitus patients with concomitant decreased sound tolerance (ST) and provide insights for developing tailored therapeutic approaches. A retrospective analysis was conducted on patient records from a tertiary university hospital's tinnitus clinic between March 2020 and June 2023. Demographic attributes and audiological profiles were reviewed. Patients were categorized into Group 1 if loudness discomfort level test outcomes were 77 dB or below, measured using an average of frequencies from 250 Hz to 8 kHz. The remaining patients were allocated to Group 2. Among the 434 tinnitus patients, 115 (26.5%) demonstrated decreased ST and were classified as Group 1. This group exhibited higher DPOAE amplitudes (p < 0.001), shortened latency, and decreased threshold of ABR wave V bilaterally (p < 0.05). No significant disparities were observed in gender, age, tinnitus handicap inventory, visual analog scale, and pure-tone audiometry results except subjective hyperacusis. Binary logistic regression analysis utilizing the forward conditional method revealed that the difference between groups was independently linked to DPOAE response at 7,277 Hz on the left side [B = 0.093, p < 0.001, EXP(B) = 1.07, 95% CI = 1.044-1.153]. Increased DPOAE amplitude and shorter and decreased ABR wave V in tinnitus patients with decreased ST might suggest a possible association with lesions in or around the superior olivary complex or higher central auditory pathway, potentially linked to the inhibition of medial olivocochlear efferents.

Otoacoustic emissions reveal the micromechanical role of organ-of-Corti cytoarchitecture in cochlear amplification.

The intricate, crystalline cytoarchitecture of the mammalian organ of Corti presumably plays an important role in cochlear amplification. As currently understood, the oblique, Y-shaped arrangement of the outer hair cells (OHCs) and phalangeal processes of the Deiters cells serves to create differential "push-pull" forces that drive the motion of the basilar membrane via the spatial feedforward and/or feedbackward of OHC forces. In concert with the cochlear traveling wave, the longitudinal separation between OHC sensing and forcing creates phase shifts that yield a form of negative damping, amplifying waves as they propagate. Unlike active forces that arise and act locally, push-pull forces are inherently directional-whereas forward-traveling waves are boosted, reverse-traveling waves are squelched. Despite their attractions, models based on push-pull amplification must contend with otoacoustic emissions (OAEs), whose existence implies that amplified energy escapes from the inner ear via mechanisms involving reverse traveling waves. We analyze hybrid local/push-pull models to determine the constraints that reflection-source OAEs place on the directionality of cochlear wave propagation. By implementing a special force-mixing control knob, we vary the mix of local and push-pull forces while leaving the forward-traveling wave unchanged. Consistency with stimulus-frequency OAEs requires that the active forces underlying cochlear wave amplification be primarily local in character, contradicting the prevailing view. By requiring that the oblique cytoarchitecture produce predominantly local forces, we reinterpret the functional role of the Y-shaped geometry, proposing that it serves not as a push-pull amplifier, but as a mechanical funnel that spatially integrates local OHC forces.

Neonatal Hearing Screening Programme And Challenges Faced By The Developing Country: A Tertiary Care Hospital Experience.

OBJECTIVE: To screen new-borns to diagnose any hearing impairment early. METHODS: The prospective, cross-sectionalstudy was conducted at the Department of Otorhinolaryngology, Head and Neck Surgery Liaquat National Hospital, Karachi, from November 1, 2020, to April 30, 2021, and new- borns of either gender aged >12h born via spontaneous vaginal delivery, induced labour, and Caesarean section. A predesigned questionnaire was used to collect detailed case history, including gestational age, duration of labour, and other prenatal, natal, and postnatal risk factors. Otoacoustic emission test was performed, and infants referred twice were scheduled for complete diagnostic evaluation and brainstem evoked response audiometry. Data was analysed using SPSS 23. RESULTS: Of the 267 neonates, 249(93.3%) passed the first screening. Of the remaining 18(6.7%) neonates, 8(44.4%) passed the second screening, while 10(55.5%) were asked to come for a follow-up after three weeks. Of them, 3(30%) returned for check-up, while 7(70%) did not show up. CONCLUSIONS: Neonatal risk factors associated with hearing loss need to be identified, and a comprehensive hearing screening programme is required for neonates.

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.

Prevalence and Auditory Characteristics of Auditory Neuropathy Spectrum Disorder in Adult Population with Sensory Neural Hearing Loss: A Hospital Based Study in South India.

Auditory neuropathy spectrum disorder (ANSD) is a heterogenous group of disorder characterized by abnormalities in auditory brainstem responses (ABR) with preserved otoacoustic emissions and/or cochlear microphonics. The aim of the study is to estimate the prevalence and evaluate the audiological characteristics of ANSD in adult population with sensory neural hearing loss. A prospective study was conducted on the adult population (≥ 18 years) attending ENT outpatients clinic at Rajiv Gandhi Government General Hospital, Chennai. All patients reported to the department with auditory and vestibular symptoms underwent case history, otoscopic examination, and routine audiological evaluation (pure tone audiometry, speech audiometry and immittance audiometry). Patients with indications of ANSD in case history and routine audiological evaluation were further evaluated using distortion product otoacoustic emissions and ABR. A total of 8682 adult population was evaluated during the period of 2017 to 2018. Out of 8682 patients, 1343 (15.46%) of them had sensory neural hearing loss of varying degrees. Out of 1343 adults with sensory neural hearing loss, 24 (1.78%) adults were diagnosed as ANSD. The prevalence of ANSD in adult population with sensory neural hearing loss in our study is 1.32% per 1000 adults. The clinical characteristics of ANSD shows impairment in speech perception irrespective of degree of hearing loss, preserved cochlear functions and abnormal ABR. Hence ANSD is not a rare clinical finding in adults with sensory neural hearing loss, but its prevalence was estimated to be lower in Indian population. Often young females are affected causing significant impairment in speech perception and disability.

Pure Tone Audiometry and Otoacoustic Emission Evaluation of Hearing Loss in Diabetic Patients in a Selected Urban Population of South-West Nigeria.

BACKGROUND: Diabetes Mellitus (DM) is a clinical condition which is characterized by persistent hyperglycemia resulting from insulin deficiency and/or insulin resistance. The spectrum of hearing impairments among patients with diabetes is wide with majority of the hearing problems not specific to patients with DM. The current study is aimed to evaluate the hearing loss in Diabetic Mellitus patients in a selected urban population of south-west Nigeria using pure tone audiometry and otoacousticemission evaluation. It will correlate the audiological findings with factors such as age, gender, glycemic status, and duration of DM. METHODS: A cross sectional progressive study was carried out from January 2021 to December 2021 on randomly selected 95 consecutive diabetic patients visiting the departments of Otorhinolaryngoloy and Medicine. RESULTS: A total of 95 DM patients attending the ENT clinics of the hospital consented and participated in the study. Their ages ranged from 43 to 82 years and had a mean of 65.3 ± 8.4 years. Majority of the patients were females (73.7%); femaleto- male ratio was approximately 3:1. About half of them were already retired (49.5%) while more than half had at least a tertiary level of education (53.7%).8.4% were reported to have discharge from their ears, 24.2% had itchy sensations and 5.3% had recurrent nasal discharge. The prevalence of hyperglycemia was 36.8% in the subjects; while another 5.3% were hypoglycemic. CONCLUSION: Hearing impairment is significantly associated with the DM and other risk factors in DM patients including older age, occupation, poor glycemic controls, undue noise and alcohol consumption.

CONTEXTE: Le diabète sucré (DM) est un état clinique caractérisé par une hyperglycémie persistante résultant d'une carence en insuline et/ou d'une résistance à l'insuline. L'étude actuelle vise à évaluer la perte auditive chez les patients atteints de diabète sucré dans une population urbaine sélectionnée du sud-ouest du Nigeria en utilisant l'audiométrie tonale et l'évaluation de l'émission otoacoustique. Elle mettra en corrélation les résultats audiologiques avec des facteurs tels que l'âge, le sexe, le statut glycémique et la durée du diabète. MÉTHODES: Une étude transversale progressive a été menée de janvier 2021 à décembre 2021 sur 95 patients diabétiques consécutifs sélectionnés au hasard et se rendant dans les départements d'oto-rhino-laryngologie et de médecine. RÉSULTATS: Au total, 95 patients diabétiques consultant les cliniques ORL de l'hôpital ont consenti à participer à l'étude. Leur âge variait de 43 à 82 ans, avec une moyenne de 65,3 ± 8,4 ans. La majorité des patients étaient des femmes (73,7 %) ; le rapport femmes-hommes était d'environ 3:1. Environ la moitié d'entre eux étaient déjà à la retraite (49,5 %), tandis que plus de la moitié avaient au moins un niveau d'éducation tertiaire (53,7%).8,4 % des patients ont déclaré avoir des écoulements dans les oreilles, 24,2 % des démangeaisons et 5,3 % des écoulements nasaux récurrents. La prévalence de l'hyperglycémie était de 36,8 % chez les sujets, tandis que 5,3 % étaient hypoglycémiques. CONCLUSION: La déficience auditive est significativement associée au diabète et à d'autres facteurs de risque chez les patients atteints de diabète, notamment l'âge avancé, la profession, les mauvais contrôles glycémiques, le bruit excessif et la consommation d'alcool. Mots-clés: Diabète sucré, Perte auditive, Audiométrie, Émission otoacoustique.

Gestational Mild COVID-19 Infection Associated Neonatal Hearing Loss: A Case-Control Study from North India.

COVID-19 infection during pregnancy is potentially dangerous to neonatal hearing, as it is the period of organogenesis, and associated hyperthermia may cause vascular damage, disruption of cell migration, and death of the dividing neuroblasts. To investigate the possible association between neonatal hearing loss and gestational mild COVID-19 infection. A prospective case-control study was conducted at a tertiary healthcare centre in North India from March 2020 to Oct 2022. Cases included the neonates born to COVID-19-positive mothers were subjected to hearing screening at 1, 3 and 6 months using otoacoustic emission (OAE) and automated auditory brainstem response (AABR). Similar protocol was applied to controls, i.e., neonates borne to mothers with no gestational history of COVID infection. Results were analyzed statistically. Our study reported that the statistical difference between groups A (n = 942) and B (n = 942) for gestational COVID-19 infection and neonatal hearing loss was insignificant at 1 month (p-value 0.272 for OAE and p-value 0.634 for AABR) and also insignificant at 3 and 6 months (p-value 0.679 for AABR, for both). The association between gestational mild COVID-19 infection during gestation and neonatal hearing loss is statistically insignificant at initial screening as well as sequential screenings.

Obstructive Sleep Apnoea Syndrome and Association of AHI Scores with Sensorineural Hearing Loss: An Early Predictor.

Obstructive sleep apnoea syndrome (OSAS) is a condition that is characterised by frequent apnoea and hypopnoea attacks occurring during sleep. The blood supply to cochlea and acoustic nerves is from terminal arteries, thereby making them susceptible to hypoxia. To compare the audiological profiles in patients with OSAS according to Apnoea Hypopnoea index (AHI) score. Descriptive study was conducted in 32 patients diagnosed to have OSAS in a tertiary referral centre over two year period. The study group was divided into mild, moderate, severe OSAS based on AHI score. The hearing evaluation was done using pure tone audiogram (PTA) and distortion product otoacoustic emission test (DPOAE). Moderate and severe OSAS participants had elevated thresholds at higher frequencies in PTA (4 kHz, 8 kHz), although this was not statistically significant. We also noticed, absent DPOAE responses at higher frequencies (4 k, 6 k, 8 k), with increase in the severity of OSAS at higher frequency, which was statistically significant (p value < 0.05). This study revealed elevated hearing thresholds at higher frequencies (4 kHz, 8 kHz) in PTA and DPOEA with an increase in the severity of OSAS. All OSAS patients, especially with AHI > 30 should be regularly screened for hearing loss.

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

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

Radiation dose to the cochlea and its association with sensorineural hearing loss in head and neck cancer-A prospective study.

AIM: To determine the effect of cochlear dose on sensorineural hearing loss in patients with head and neck cancer treated by radiotherapy and chemoradiotherapy. MATERIALS AND METHOD: A two-year longitudinal study was conducted on 130 subjects with various head and neck malignancies who were receiving radiotherapy or chemoradiation. 56 patients received only radiotherapy while 74 patients received concurrent chemoradiation five days a week at a dose of 66-70 Gy. They were categorized as having a radiation dose to the cochlea of <35 Gy, <45 Gy or >45 Gy. Pre- and post-therapy audiological evaluation was done using a Pure-tone audiogram, distortion product otoacoustic emission, and impedence. Hearing thresholds were measured at frequencies up to 16,000 Hz. RESULTS: Out of 130 patients 56 received RT alone and 74 received CTRT. There was statistically significant (p value <0.005) difference in Pure-tone audiometry assessment in both the RT and CTRT groups between subjects who received more than and <45 Gy of radiation to the cochlea. There was no significant difference in distortion product otoacoustic emission assessment between patients who received >45 Gy and <45 Gy radiation to the cochlea. Comparison between subjects who received radiation dose of <35 Gy and >45 Gy revealed significant results in the degree of hearing loss (p value <0.005). CONCLUSION: We observed that patients who received >45 Gy of radiation had more sensorineural hearing loss compared to patients who received <45 Gy. A cochlear dose of <35 Gy is associated with significantly lower hearing loss compared to higher doses. We would like to conclude by emphasizing the importance of regular audiological assessments prior to and post radiotherapy and chemoradiotherapy, with regular follow-ups encouraged over a longer period to improve the quality of life in patients with head and neck malignancy.

Magnitude of medial olivocochlear reflex assayed by tone-burst-evoked otoacoustic emissions: reliability and comparison with click-evoked emissions.

OBJECTIVE: The purpose of this pilot study was to evaluate the magnitude of the medial olivocochlear reflex (MOCR) estimated by the reduction in tone-burst evoked otoacoustic emissions (TBOAEs) measured at three levels and at three frequencies in response to fixed contralateral white noise. Results were compared with commonly used click-evoked otoacoustic emissions (CEOAEs). DESIGN: TBOAEs and CEOAEs, with and without contralateral 60 dB SPL white noise, were measured in response to stimulation at 55, 65, and 75 dB peSPL. In each subject, the set of measurements was performed twice. Of particular interest were the MOCR and its repeatability. STUDY SAMPLE: 15 normally hearing persons (13 women, average age 32.3 years, SD = 8.1). RESULTS: For both CEOAE and TBOAEs, the reliability of the MOCR was much better for broadband measurements than for half-octave-band filtered estimates. At the same time, the reliability of MOCR in half-octave bands was higher for TBOAEs than for CEOAEs, especially at 2 and 4 kHz. CONCLUSIONS: For general applications where broadband MOCR is of interest, the highest magnitude and reliability is provided by CEOAEs. However, TBOAEs may be better if a particular frequency band is of interest.

Bandpass Shape of Distortion-Product Otoacoustic Emission Ratio Functions Reflects Cochlear Frequency Tuning in Normal-Hearing Mice.

The frequency selectivity of the mammalian auditory system is critical for discriminating complex sounds like speech. This selectivity derives from the sharp tuning of the cochlea's mechanical response to sound, which is largely attributed to the amplification of cochlear vibrations by outer hair cells (OHCs). Due to its nonlinearity, the amplification process also leads to the generation of distortion products (DPs), some of which propagate out to the ear canal as DP otoacoustic emissions (DPOAEs). However, the insight that these signals provide about the tuned micro- and macro-mechanics underlying their generation remains unclear. Using optical coherence tomography to measure cochlear vibrations in mice, we show that the cochlea's frequency tuning is reflected in the bandpass shape that is observed in DPOAE amplitudes when the ratio of the two evoking stimulus frequencies is varied (here termed DPOAE "ratio functions"). The tuning sharpness of DPOAE ratio functions and cochlear vibrations co-varied with stimulus level, with a similar quantitative agreement in tuning sharpness observed for both apical and mid-cochlear locations. Measurement of intracochlear DPs revealed that the tuning of the DPOAE ratio functions was not caused by mechanisms that shape DPs locally near where they are generated. Instead, simple model simulations indicate that the bandpass shape is due to a more global wave interference phenomenon. It appears that the filtering of DPOAEs by wave interactions over an extended spatial region allows them to provide a window onto the frequency tuning of single cochlear locations.

The association of auditory function measures with low-level methylmercury from oceanic fish consumption and mercury vapor from amalgam: The Seychelles Child Development Study Nutrition 1 Cohort.

BACKGROUND: Some authors have reported that low-level exposure to methylmercury (MeHg) adversely impacts measures of auditory function. These reports, however, are not consistent in their findings. Consequently, we examined auditory function in a population exposed to low-level methylmercury (MeHg) exposure from fish consumption and to mercury vapor (Hg0) from dental amalgams. We analyzed their associations with the participants hearing acuity, absolute and interwave ABR latencies, and otoacoustic emissions (distortion product/DPOAE and click evoked/CEOAE). DESIGN: We administered an audiometry test battery to 246 participants from the Seychelles Child Development Study (SCDS) Nutrition Cohort 1 (NC1) at 9 years of age. The test battery included standard pure-tone audiometry, tympanometry, Auditory Brainstem Responses (ABR) and Distortion Product and Click Evoked Otoacoustic Emissions (DPOAE and CEOAE) testing. We measured prenatal MeHg exposure in maternal hair and postnatal MeHg in children's hair. We approximated prenatal Hg0 exposure using maternal amalgam surface area and postnatal Hg0 using children amalgam surface area. Complete exposure records and audiometric data were available on 210 participants and in them we analyzed the association of MeHg and Hg0 exposures with auditory outcomes using covariate-adjusted linear regression models adjusted for sex and tympanometric pressure. RESULTS: Hg exposures were similar for both sexes. Seven of the 210 evaluable participants examined had either a mild (5) or moderate (2) hearing loss. Four had a mild monaural hearing loss and 3 had either a mild (1) or moderate (2) bilateral hearing loss. No participant had greater than a moderate hearing loss in either ear. Hg exposures were higher in participants with either a mild or moderate hearing loss, but these differences were not statistically significant. Among the 210 with complete data, neither prenatal nor postnatal MeHg nor Hg0 exposure was statistically significantly associated with any of the ABR endpoints (p > 0.05 for all 72 associations). Neither prenatal nor postnatal Hg0 exposure was associated with any of the OAE endpoints (p > 0.05). MeHg exposure was statistically associated with 6 of the 56 DPOAE endpoints (p-values between 0.0001 and 0.023), but none of the 40 CEOAE endpoints. Two of the associations occurred with prenatal MeHg exposures and 1 of those would suggest a beneficial effect. Four of the other associations occurred with postnatal MeHg exposures with only 2 found in left ears of both males and females and the other 2 in the left and right ear of females at only one frequency. CONCLUSION: Overall, these data do not present a clear and consistent pattern to suggest that the auditory system is negatively affected by low-level methylmercury exposure due to dietary consumption of oceanic fish or mercury vapor exposure from dental amalgams.

Cochlear Function in Adults Exposed to Severe Acute Respiratory Syndrome Coronavirus 2.

INTRODUCTION: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a viral infection with a wide variety of symptoms, including fever, coughing, sneezing, fatigue, and a loss of taste and smell. Moreover, there are some recent studies that investigate the effects of SARS-CoV-2 on hearing and auditory performance. With this current study, we investigate the early effects of the coronavirus disease on hair cells in the cochlea. METHODS: In the current study, there were 25 subjects (17 females, 8 males) who tested positive for polymerase chain reaction on nasopharyngeal swabs. They had reported normal auditory functions and no history of otology before SARS-CoV-2. To determine auditory functions, pure-tone audiometry, otoacoustic emissions (OAE) tests, and threshold equalizing noise (TEN) tests were used. RESULTS: Although the hearing thresholds increased at higher frequencies, they were within normal limits according to four-frequency pure-tone averages. All participants had normal OAE, and there were no detected dead regions for any of the subjects. Even so, there were significant increases in hearing thresholds in TEN. CONCLUSION: There is no cochlear dysfunction discovered by OAE and TEN in SARS-CoV-2-affected individuals. Nonetheless, the increase in hearing thresholds at higher frequencies, other than the pure-tone average frequencies detected by TEN, and the decrease in the presence of detected OAE could be related to deterioration in the basal part of the cochlea.