Distortion product otoacoustic emissions in newborn babies with and without late-term maternal iron deficiency anaemia

Background:Studies on animals have demonstrated that maternal iron deficiency anaemia(IDA)could result in decreased cochlear sensory hair cells and reduced amplitudes of distortion-product otoacoustic emissions(DPOAEs)of young guinea pigs.Thus,it is essential to study the functioning of cochlear hair cells using DPOAEs in human newborn babies with maternal IDA.The current study explores maternal IDA’s effect on DPOAEs in newborn babies.Method:A total of 110 newborn babies with gestational age≥34 weeks were considered and a‘betweensubjects’design was used.The participants were divided into 3 groups-“Normal”(61 babies without maternal IDA),“Mild”(28 babies with mild maternal IDA)and“Moderate”(21 babies with moderate maternal IDA).The cord blood was collected and the DPOAEs were recorded for each baby for a range of frequencies(1 k 8 kHz)and a range of intensities(7040 dB SPL in 10 dB steps).Results:The analysis of both DP-gram and DP input-output(I/O)function showed that there was no significant difference(p>0.05)across the normal,mild,and moderate groups in the overall presence of DPOAEs as well as the amplitude across frequencies or intensities(7040 dB SPL).Also,the overall correlation of RBC indices with DPOAE amplitude across frequencies as well as the slope of the I/O function showed no relationship.Conclusion:The current study concludes that there is no effect of late-term maternal IDA on the DPOAEs of newborn babies.

Backward Propagation of Otoacoustic Emissions

Normal mammalian ears not only detect but also generate sounds. The ear-generated sounds, i.e., otoacoustic emissions (OAEs), can be measured in the external ear canal using a tiny sensitive microphone. In spite of wide applications of OAEs in diagnosis of hearing disorders and in studies of cochlear functions, the question of how the cochlea emits sounds remains unclear. The current dominating theory is that the OAE reaches the cochlear base through a backward traveling wave. However, recently published works, including experimental data on the spatial pattern of basilar membrane vibrations at the emission frequency, demonstrated only forward traveling waves and no signs of backward traveling waves. These new findings indicate that the cochlea emits sounds through cochlear fluids as compression waves rather than through the basilar membrane as backward traveling waves. This article reviews different mechanisms of the backward propagation of OAEs and summarizes recent experimental results.

Isoflurane anesthesia suppresses distortion product otoacoustic emissions in rats

A commonly used anesthetic, isoflurane, can impair auditory function in a dose-dependent manner. However, in rats, isoflurane-induced auditory impairments have only been assessed with auditory brainstem responses; a measure which is unable to distinguish if changes originate from the central or peripheral auditory system. Studies performed in other species, such as mice and guinea-pigs, suggests auditory impairment stems from disrupted OHC amplification. Despite the wide use of the rat in auditory research, these observations have yet to be replicated in the rat animal model. This study used distortion product otoacoustic emissions to assess outer hair cell function in rats that were anesthetized with either isoflurane or a ketamine/xylazine cocktail for approximately 45 min. Results indicate that isoflurane can significantly reduce DPOAE amplitudes compared to ketamine/xylazine, and that responses were more variable with isoflurane than ketamine/xylazine over the 45-min test period. Based on these observations, isoflurane should be used with caution when assessing peripheral auditory function to avoid potentially confounding effects.

An Overview of Electrically Evoked Otoacoustic Emissions in the Mammalian Cochlea

Alternating currents injected into the cochlea are able to evoke outer hair cell-mediated basilar membrane motion, thus give rise to production of otoacoustic emissions. This electrically evoked otoacoustic emission(EEOAE) provides a useful tool for the research of out hair cell electromotility in vivo. This article reviews the research work on EEOAEs in mammals. Features of the EEOAEs and theories of their generation are introduced. Methods of EEOAE measurement are also described.

MEASUREMENT OF AMPLITUDE AND DELAY OF STIMULUS FREQUENCY OTOACOUSTIC EMISSIONS

Although stimulus frequency otoacoustic emissions (SFOAEs) have been used as a non-invasive measure of cochlear mechanics, clinical and experimental application of SFOAEs has been limited by difficulties in accurately deriving quantitative information from sound pressure measured in the ear canal. In this study, a novel signal processing method for multicomponent analysis (MCA) was used to measure the amplitude and delay of the SFOAE. This report shows the delay-frequency distribution of the SFOAE measured from the human ear. A low level acoustical suppressor near the probe tone significantly suppressed the SFOAE, strongly indicating that the SFOAE was generated at characteristic frequency locations. Information derived from this method may reveal more details of cochlear mechanics in the human ear.

Spontaneous Otoacoustic Emissions in Tinnitus Patients

Otoacoustic emissions (OAEs) are believed to be the products of active cochlear mechanics. They are generally associated with relatively intact outer hair cell function. OAEs usually decrease or become undetectable when hearing loss of cochlear origin exceeds 40-50 dB HL. Subjective tinnitus is a perception of sound without detectable corresponding source. It is most often seen in patients with hearing loss. It is also frequently seen in patients with head injuries. Studies have suggested that the prevalence of spontaneous otoacoustic emissions(SOAEs) is lower in patients with hearing loss and tinnitus than in normal population. There have also been reports on association between tinnitus and SOAEs of unusually high amplitudes, which can be controlled by aspirin administration. The current paper is a preliminary review of clinical data collected from a group of tinnitus patients in an attempt to elucidate on the relationship between SOAEs and tinnitus from a clinical point of view. Audiometric, tinnitus and SOAE data from 59 patients seen at the Oregon Health & Science University Tinnitus Clinic were retrospectively studied. Fifty-four of these 59 patients showed sensorineural hearing loss of various degrees at the time of evaluation, mostly affecting high frequencies. SOAEs were detected in 26 ears (22%) of 18 patients(30.5%). There was no difference in SOAE prevalence between male and female patients. SOAEs were recorded in four of the five patients whose pure tone thresholds were within normal limits up to 8000 Hz. SOAEs appeared to be recorded at a higher rate in patients whose tinnitus started following motor vehicle accidents or head injuries(5/10) than in other patients. Time course of tinnitus did not appear to affect SOAE detection rate. There were no correlations between SOAE frequency and matched tinnitus pitch or frequency of maximum hearing loss. Significance of these findings is discussed.

Evaluation of SON’OR^(█),a Medical Device for Provoked Otoacoustic Emissions and Brainstem Evoked Response Audiometry Made in Cameroon

Background: There is a huge gap in the audiological care in Africa by comparison with Western countries. Its main reason is the prohibitive cost of the medical devices used to screen or diagnose patients. A Cameroonian team tackled this problem by developing a medical device (SON’OR©) which integrates a new instrumentation amplifier structure dedicated to perform otoacoustic emissions (OAE) and brainstem evoked response audiometry (BERA). The major technical challenges to perform OAE and BERA are the synchronization and the amplification of signals of very low amplitude. In this work, we emphasize on the general criteria necessary and indispensable to achieve an optimal amplification. The application of a novel instrumentation amplifier structure characterized by its optimized noise factor in the case of BERA and OEA emissions provides simulations and experimental results fully in line with forecasts. The design of SON’OR©is based on general techniques of electronic instrumentation to which we associated the new instrumentation amplifier structure. Objective: To report the clinical evaluation of SON’OR©as a screening and diagnostic tool. Methods: We conducted a cross sectional comparative study in Centre Hospitalier d’Essos in Yaoundé. We tested SON’OR©on two sets of subjects, one for OAE with OTODYNAMICS Echoport ILO 292-II as gold standard and the other for BERA with NEUROSOFT NEURO AUDIO©as gold standard. Each patient was tested with both devices and then we studied the inter device differences and calculated the sensitivity, specificity, positive predictive value and negative predictive value for each test. Results: We got 52 subjects for OEA and 51 for BERA testing. Sex ratio was 1 woman for 2 men in both groups. Mean age was 24.86(SD = 10.53) and 26.33 (10.55) for OAE and BERA groups respectively. SON’OR©had good performances, showing sensitivity of 92.85%/95%, specificity of 96.77%/90.47%, positive predictive value of 95.21%/93.44% and negative predictive value of 95.23%/92.68% for OAE/ BERA respectively. Conclusion: SON’OR©has good characteristics as a medical diagnostic tool. Furthermore its stability and performances in poor electrical conditions make it a robust device really suited for resource limited settings.

Characterization of spontaneous otoacoustic emissions in 2–4 day old neonates with respect to gender and ear

BACKGROUND： Spontaneous otoacoustic emissions （SOAEs） are regarded as a valuable audio- metric parameter that objectively reflects the function of outer hair cells （OHCs）. Many studies have reported that the incidence of SOAEs in adults is less than 50%. Therefore, measurement of SOAEs may be of little value to clinical examinations. However, the incidence of SOAEs in infants and neonates is higher than in adults. OBJECTIVE： To analyze the basic characteristics of SOAEs in 2–4 day old neonates, and to demonstrate the difference in OHC function between sexes and ears. DESIGN, TIME AND SETTING： Neurophysiological contrast study, performed in the Department of Neonates, Beijing Chaoyang Hospital, Capital Medical University, between December 2007 and August 2008. PARTICIPANTS： A total of 112 newborns （224 ears） consisting of 59 females and 53 males were included in this study. METHODS： The probe was adapted and embedded in the neonate external auditory canal with a foam rubber earplug after checking and clearing up the outer ear canal. The presence of SOAEs was determined when the signal amplitude had a clear peak exceeding –30 dB, or was 3 dB above the noise floor. MAIN OUTCOME MEASURES： The incidence of SOAEs, the number of SOAE signal peaks, and the maximal tension of SOAEs. RESULTS： The incidence in females （79.7%） was higher than males （76.4%） （P 〉 0.05）, and the incidence in right ears （86.6%） was higher than in left ears （69.6%） （P 〈 0.05）. There were no significant difference in the number of SOAE peaks between females and males （4.49 vs. 4.28）, or between right ears and left ears （4.62 vs. 4.12） （P 〉 0.05）. The mean maximum SOAE level per ear in females （–3.29 ± 9.28） dB sound pressure level （SPL） was slightly higher than that in males （–3.91 ± 9.14） dB SPL （P 〉 0.05）. Also, the mean maximum SOAE level in right ears （–2.03 ± 9.11） dB SPL was higher than in left ears （–5.50 ± 9.65） dB SPL （P 〈 0.05）. The maximum SOAE level showed a positive correlation with maximum SOAE number in emitting ears （r = 0.55, P 〈 0.01）. CONCLUSION： The incidence of SOAEs in neonates is high （78.1%） within 4 days of birth. The in-cidence of SOAEs and the maximum SOAE level exhibited a significant difference between right and left ears, but the difference between sexes was insignificant. Both the strongest SOAE signal peak and number of SOAEs per ear are representative of the function OHCs.

Otoacoustic emissions value in patients with idiopathic sudden sensorineural hearing loss

Objectives:This study aimed to determine the prognostic value of otoacoustic emissions(OAEs)in idiopathic sudden sensorineural hearing loss patients.Methods:The study included 30 subjects with unilateral idiopathic sudden sensorineural hearing loss(ISSNHL).Each patient was evaluated four times:at baseline and after one week,one month,and three months of treatment.During each visit,each patient was subjected to full audiological history,otoscopic examination,basic audiological evaluations,and transiently evoked and distortion product otoacoustic emission(TEOAEs&DEOAEs).Results:The hearing thresholds(frequency range 250e8000 Hz)and word recognition scores of patients with detectable TEOAEs and DPOAEs improved significantly,whereas no significant improvements were observed in those with no response.Conclusion:Hearing improvement is better in patients with detectable TEOAEs and DPOAEs.As a result,TEOAEs and DPOAEs are recommended as routine tests in all SSNHL patients to predict outcomes and monitor treatment as TEOAEs and DPOAEs reflect the cochlear OHCs activity.

Otoacoustic emissions recorded in people with chronic migraine

Migraine,a moderate to severe chronic headache occurring on one or both sides,is a common disease affects young people.Although hearing loss in subjects with migraine is not rare,the correlation of migraine with hearing loss is not clear.In this study,we examined hearing loss in young migraine subjects to determine if migraine may be a factor in causing cochlear dysfunction.Seven college students with migraine and three age matched subjects without history of migraine were assessed using extended high frequency audiometry and distortion product otoacoustic emissions(DPOAEs).There was no significant difference in regular audiomeiry threshold between the migraine group and the control group.However,high frequency audiometry(9-16 kHz) showed thresholds at 25 dB nHL or higher in six out of twenty ears in the migraine group.The amplitude of DPOAEs were reduced for more than 10 dB in the migraine group in comparison with the control group.These data suggest that migraine may affect cochlear dysfunction evidenced by the reduced amplitude of DPOAE and high frequency pure-tone audiometry.

Effects of glutamate on distortion-product otoacoustic emissions and auditory brainstem responses in guinea pigs

Objectives To investigate changes in evoked potentials and structure of the guinea pig cochleae during whole cochlear perfusion with glutamate. Methods CM, CAP, DPOAE, and ABR were recorded as indicators of cochlear functions during whole cochlear perfusion. The morphology of the cochlea was studied via transmission electron microscopy. Results There were no significant changes in DPOAE amplitude before and after glutamate perfusion. CM I/O function remained nonlinear during perfusion. ABR latencies were delayed following glutamate perfusion. The average CAP threshold was elevated 35 dB SPL following glutamate perfusion.. The OHCs appeared normal, but the IHCs and afferent dendrites showed cytoplasmic blebs after glutamate perfusion. Conclusions While being a primary amino acid neurotransmitter at the synapses between hair cells and spiral ganglion neurons, excessive glutamate is neurotoxic and can destroy IHCs and spiral ganglion neurons. The technique used in this study can also be used to build an animal model of auditory neuropathy.

Detection of transient evoked otoacoustic emissions by adaptive signal enhancement

Otoacoustic emissions (OAEs) has been considered as an excellent objective tool in clinics for diagnosing hearing loss. The signal-to-noise ratio (SNR) and correlation coefficient of OAEs are very important for the purpose of diagnosis. An adaptive signal enhancer (ASE) based on the Least Mean Square (LMS) algorithm is presented to detect transient evoked OAEs (TEOAEs). The TEOAEs detection results from 106 ears show that ASE reaches better estimation of TEOAEs than a conventional ensemble averaging (EA) technique. With the ASE, the improvement of SNR was increased faster than that with the EA and the number of sweeps required can be markedly reduced. The detection time with ASE could be shortened by about 50% in comparison with that of EA.

Correlation among thresholds of evoked otoacoustic emissions,behavioral responses and auditory brainstem responses

In 35 adult human subjects (58 ears) thresholds of rarefaction click evoked otoacoustic emission (EOAE), behavioral response (BR) and auditory brainstem response (ABR) were measured and compared, and correlation coefficients (r) among them calculated. The results revealed that 86 % of the measured thresholds were in the range from 10 to 45 dB (nHL) for EOAE, 88 % from 10 to 25 dB for BR and 88 % from 10 to 35 for ABR. The correlation coefficients for the whole threshold sample were 0.415 (p< 0.002) for EOAE vs. BR, 0.501 (p< 0.001) for EOAE vs. ABR and 0.702 (p< 0.001) for ABR vs. BR, all indicating highly significant correlation. However, for those ears whose BR, ABR or EOAE thresholds were elevated, equaling to or exceeding 25 dB, there is no significant correlation between thresholds of EOAE and BR and of EOAE and ABR (r range: 0.176-0.310, p>0.05). In contrast, significant correlation between BR and ABR thresholds in the same conditions still remained (r: 0.533-0.720, p<0.05). The experimental results indicate that the correlation between EOAE and hearing thresholds is significant only for subjects with normal or slightly lost hearing. EOAE is valuable in audiometry only as an accessory tool.

Efficient Authentication System Using Wavelet Embeddings of Otoacoustic Emission Signals

Biometrics,which has become integrated with our daily lives,could fall prey to falsification attacks,leading to security concerns.In our paper,we use Transient Evoked Otoacoustic Emissions(TEOAE)that are generated by the human cochlea in response to an external sound stimulus,as a biometric modality.TEOAE are robust to falsification attacks,as the uniqueness of an individual’s inner ear cannot be impersonated.In this study,we use both the raw 1D TEOAE signals,as well as the 2D time-frequency representation of the signal using Continuous Wavelet Transform(CWT).We use 1D and 2D Convolutional Neural Networks(CNN)for the former and latter,respectively,to derive the feature maps.The corresponding lower-dimensional feature maps are obtained using principal component analysis,which is then used as features to build classifiers using machine learning techniques for the task of person identification.T-SNE plots of these feature maps show that they discriminate well among the subjects.Among the various architectures explored,we achieve a best-performing accuracy of 98.95%and 100%using the feature maps of the 1D-CNN and 2D-CNN,respectively,with the latter performance being an improvement over all the earlier works.This performance makes the TEOAE based person identification systems deployable in real-world situations,along with the added advantage of robustness to falsification attacks.

Effect of age on click-evoked otoacoustic emission A systematic review

OBJECTIVE：The aims of this study were to investigate the changes of the total intensity of transient evoked otoacoustic emission（TEOAE） and signal-to-noise ratio in various frequency bands as a function of aging,and to explore the role of age-related decline of cochlear outer hair cells.DATA SOURCES：The literature was searched using the PubMed database using ＇transient-evoked otoacoustic emissions＇ as a keyword.Articles were limited as follows：Species was ＇Humans＇;languages were ＇English and Chinese＇;publication date between 1990-01-01 and 2010-12-31.The references of the found were also searched to obtain additional articles.DATA SELECTION：Inclusion criteria：（1） Articles should involve the total TEOAE level or signal-to-noise ratio.（2） The measurement and analysis system used was Otodynamics ILO analysis system（ILO88,ILO92,ILO96 or ILO292）.（3） Studies involved groups of greater than 10 subjects and TEOAE results were from normally hearing ears.（4） If more papers from the same author or laboratory analyzed the same subjects,only one was used.MAIN OUTCOME MEASURES：The correlations of the age scale with the total level and signal-to-noise ratio of TEOAE was determined,respectively.RESULTS：（1） TEOAE total level gradually increased until 2 months of age,and then decreased with increasing age.Significant negative correlations between total TEOAE level and age were found（r =-0.885,P = 0.000）.（2） The most rapid decrease of TEOAE amplitude occurred at 1 year old.The total TEOAE level decreased about 4.25 dB SPL between 2 months to 1 year old,then about 0.26-0.52 dB SPL from 1 year to 10 years old,about 0.23 dB SPL from 11 years to 25 years old,and about 0.14 dB SPL from 26 years to 60 years old.（3） The signal-to-noise ratio in the frequency bands centered at 1.5,2,3 and 4 kHz decreased with increasing age after 2 months of age.Significant negative correlations between the signal-to-noise ratio and age were found for frequency bands ranging from 1.5 kHz to 4 kHz,with the highest correlations at 4 kHz（r =-0.890,P 〈 0.01）,then at 3 kHz（r =-0.889,P 〈 0.01）,at 2 kHz（r =-0.850,P 〈 0.01） and at 1.5 kHz（r =-0.705,P 〈 0.05）.Conversely,a positive correlation between the signal-to-noise ratio centered at 1 kHz and age was found,but was not statistically significant（r = 0.298,P = 0.374）.CONCLUSION：The total TEOAE response level decreased with increasing age after the first 2 months of age.The signal-to-noise ratio also decreased with increasing age in frequency bands above 1.5 kHz.The signal-to-noise ratio in higher frequencies decreased faster than in lower frequencies,leading to the maximum signal-to-noise ratio shift form 3.2-4.0 kHz in neonates to 1.5 kHz in adults,and further decreasing the total TEOAE response level.The age-related TEOAE spectrum peak shift is most likely because the outer hair cells functioning in higher frequencies are more prone to damage than those for lower frequencies.

Auditory function in symptomatic patients recovered from SARS-CoV-2 and unexposed patients:An analytical cross-sectional study

Objective:To describe audiological symptoms,audiometric profile,and distortion product otoacoustic emission in symptomatic patients recovering from SARS-CoV-2 infection(positive RT-PCR test)and asymptomatic patients(negative RT-PCR test).Methods:An analytical cross-sectional study was conducted using data obtained from clinical charts,physical examination,audiometry,and distortion product otoacoustic emission on 40 patients[case patients(CP)]recovering from SARS-CoV-2 infection diagnosed by a positive RT-PCR test and 22asymptomatic participants with a negative RT-PCR test[non-case(NC)].Results:Sixty-two patients(mean age:31.1 and 28.2 years in the CP and NC groups,respectively)were included.All participants were young without significant comorbidities,risk factors for hearing loss or otological history.Vertigo(5%),tinnitus(17.5%)and aural fullness/hearing loss(35%)were found in the CP group.A statistically significant difference was found in specific frequencies(1000,4000,and 8000 Hz)and pure tone average(low and high conversational frequencies with increased threshold in the PC group compared with the NC group),which was not found in distortion product otoacoustic emission.Conclusion:Audiovestibular symptoms are frequent in symptomatic patients recovering from SARS-CoV-2 infection.SARS-CoV-2 infection was consistently associated with an increased audiometric hearing threshold at specific frequencies and low tone average.

Obstructive Sleep Apnea-Hypopnea Ssyndrome and Hearing in Children

Objective To explore the relationship between hypoxemia and hearing in children with obstructive sleep apnea-hypopnea syndrome. Methods Auditory brainstem responses (ABRs) were recorded in 68 ears and distortion product otoacoustic emissions (DPOAEs) in 60 ears in children with OSAHS and type "A" tym-panograms, and in 30 ears in normal children. Results ABR latencies of waves I, III and V, and I-III, III-V and I-V intervals were not statistically different between OSAHS and normal children. Wave I latency was delayed in children with OSAHS compared to normal children3 (P < 0.05). DPOAE amplitudes in children with mild OSAHS were lower than normal children at 8 kHz (P < 0.05). DPOAEs were lower at 6 kHz and 8 kHz in children with moderate/severe OSAHS than normal children (P < 0.05). Conclusion Cochlear function was affected when AHI was at or greater than 10/hour. ABR and DPOAE can be used to detect early changes in auditory function in children with OSAHS.

Neurophysiological characteristics in infants and young children with auditory neuropathy

Objective:To analyze neurophysiological characteristics in infants and young children with auditory neuropathy(AN) and explore their clinical significance.Methods: Audiological measurements(acoustic immittance, EOAEs, ABR, CM, MLR and ERPs) and peripheral neurological tests were conducted and evaluated in 13 infants and young children with AN. Six of them received high-resolution temporal bone CT scans and/or cerebral MRI examinations.Results: All of the children showed type “A” tympanograms with abseatation of stapedial reflexes. EOAEs were normal in 12 of 13 subjects. In one child who had a history of anoxia during the birth,the EOAEs were not elicited. Click-evoked ABRs were absent in 12 of 13 subjects when maximum output of the instrument was reached. The CM potentials were presented bilaterally in all individuals,which were independent of the EOAEs and ABR. Of eight cases tested,all had clear MLR and six showed normal ERPs(P300 and MMN). Peripheral neurological tests and radiological findings were within the normal ranges. Conclusion: The diagnosis of AN in infants and young children should focus on analyzing their neurophysiological characteristics,especially on CM,MLR and ERPs. Combined use of EOAEs, ABR and CM was recommended for hearing screening on newborns with high risk factors.

Early detection of noise-induced hearing loss

BACKGROUND Noise-induced hearing loss(NIHL)is the second most common acquired hearing loss following presbycusis.Exposure to recreational noise and minimal use of hearing protection increase the prevalence of NIHL in young females.NIHL is irreversible.Identifying minor hearing pathologies before they progress to hearing problems that affect daily life is crucial.AIM To compare the advantages and disadvantages of extended high frequency(EHF)and otoacoustic emission and determine an indicator of hearing pathologies at the early sub-clinical stage.METHODS This cross-sectional study was implemented in West China Hospital of Sichuan University from May to September 2019.A total of 86 participants,aged 18-22 years,were recruited to establish normative thresholds for EHF.Another 159 adults,aged 18-25 years with normal hearing(0.25-8 kHz≤25 dBHL),were allocated to low noise and noise exposure groups.Distortion otoacoustic emission(DPOAE),transient evoked otoacoustic emissions(TEOAE),and EHF were assessed in the two groups to determine the superior technique for detecting early-stage noise-induced pathologies.The chi-square test was used to assess the noise and low noise exposure groups with respect to extended high-frequency audiometry(EHFA),DPOAE,and TEOAE.P≤0.05 was considered statistically significant.RESULTS A total of 86 participants(66 females and 20 males)aged between 18 and 22(average:20.58±1.13)years were recruited to establish normative thresholds for EHF.The normative thresholds for 9,10,11.2,12.5,14,16,18,and 20 kHz were 15,10,20,15,15,20,28,and 0 dBHL,respectively.A total of 201 participants were recruited and examined for eligibility.Among them,159 adults aged between 18 and 25 years were eligible in this study.No statistical difference was detected between the noise exposure and the low noise exposure groups using EHFA,DPOAE,and TEOAE(P>0.05)except in the right ear at 4 kHz using TEOAE(abnormal rate 20.4%vs 5.2%,respectively;P=0.05).CONCLUSION These results showed TEOAE as the earliest indicator of minor pathology compared to DPOAE and EHFA.However,a multicenter controlled study or prospective study is essential to verify these results.

A METHOD FOR ESTABLISHING AN ANIMAL MODEL OF LIKE-AUDITARY NEUROPATHY

Objective: To establish an animal model of like-auditory neuropathy in neonatal rat. Methods The ani-mals were injected with phenylhydrazine hydrochloride or saline at 7-day of age. ABR and DPOAE were performed to assess the auditory function. The cochlea basilar membrane stretched preparation and cochlear frozen sections were prepared for immunohistochemical staining to examine the morphological change of hair cells and spiral ganglion cells (SGNs). Results At 7-day age the ABR waveI, III, V, latencies andI-III,I-V IWIs in the experimental group were significantly prolonged compared with those in the control group. The ABR thresholds were also elevated in the experimental group. We found there is no significant differ-ence in DPOAE in phenylhydrazine hydrochloride exposure group compare to control group. The cochlear hair cells showed no signs of loss in both group, but the total number of neurofilaments positive cells in SGNs were significantly reduced in the phenylhydrazine treated animals. Conclusion Our study suggests that phenylhydrazine hydrochloride can change the auditory function and induce peripheral nerve pathology by targeted mainly the SGNs in neonatal rat.