Normal Distortion Product Otoacoustic Emissions Research Articles

Chronic stress induced loudness hyperacusis, sound avoidance and auditory cortex hyperactivity

Hyperacusis, a debilitating loudness intolerance disorder, has been linked to chronic stress and adrenal insufficiency. To investigate the role of chronic stress, rats were chronically treated with corticosterone (CORT) stress hormone. Chronic CORT produced behavioral evidence of loudness hyperacusis, sound avoidance hyperacusis, and abnormal temporal integration of loudness. CORT treatment did not disrupt cochlear or brainstem function as reflected by normal distortion product otoacoustic emissions, compound action potentials, acoustic startle reflexex, and auditory brainstem responses. In contrast, the evoked response from the auditory cortex was enhanced up to three fold after CORT treatment. This hyperactivity was associated with a significant increase in glucocorticoid receptors in auditory cortex layers II/III and VI. Basal serum CORT levels remained normal after chronic CORT stress whereas reactive serum CORT levels evoked by acute restraint stress were blunted (reduced) after chronic CORT stress; similar changes were observed after chronic, intense noise stress. Taken together, our results show for the first time that chronic stress can induce hyperacusis and sound avoidance. A model is proposed in which chronic stress creates a subclinical state of adrenal insufficiency that establishes the necessary conditions for inducing hyperacusis.

Unexplained multi-sensory neuropathy syndrome in young Tanzanian adults.

A unique syndrome affecting young adults of unexplained hearing loss often associated with uncorrectable poor visual acuity and lower extremity numbness is endemic in Dar es Salaam. This study characterized the hearing loss, associated it with other symptoms, and gathered information on potential causes. Forty-seven patients (23 men, 24 women) <40 years old with a symptom consistent with the syndrome, negative syphilis test, and no head injury history were recruited from Muhimbili National Hospital. 18 controls (10 men, 8 women) were recruited from the same neighborhoods as patients. Hearing ability and cochlear outer hair cell function (distortion-product otoacoustic emissions (DPOAEs)) were assessed, as were visual acuity and color vision. Peripheral neuropathy was evaluated using the Michigan Neuropathy Screening Instrument (MNSI), and physical examination. Blood C-reactive protein levels and toenail trace metal concentrations were measured. Environmental exposures were elicited using a questionnaire. Patients with at least two of the following signs were defined as having the syndrome: poor hearing with normal DPOAEs, vision not correctable to better than 20/30, or a MNSI score greater than 4. 29 participants met the case definition. CRP levels did not differ between groups but manganese, cobalt and tin levels were each greater in the cases than controls. No other environmental exposure differences were noted. Toenail manganese, cobalt, and tin levels were higher in those with the syndrome. These metals are potential neurotoxins suggesting a possible environmental origin for this unique and debilitating syndrome.

Unexplained Multi-Sensory Neuropathy Syndrome in Young Tanzanian Adults

Background: A unique syndrome affecting young adults of unexplained hearing loss often associated with uncorrectable poor visual acuity and lower extremity numbness is endemic in Dar es Salaam. This study characterized the hearing loss, associated it with other symptoms, and gathered information on potential causes. Methods: Forty-seven patients (23 men, 24 women) <40 years old with a symptom consistent with the syndrome, negative syphilis test, and no head injury history were recruited from Muhimbili National Hospital. 18 controls (10 men, 8 women) were recruited from the same neighborhoods as patients. Hearing ability and cochlear outer hair cell function (distortion-product otoacoustic emissions (DPOAEs)) were assessed, as were visual acuity and color vision. Peripheral neuropathy was evaluated using the Michigan Neuropathy Screening Instrument (MNSI), and physical examination. Blood C-reactive protein levels and toenail trace metal concentrations were measured. Environmental exposures were elicited using a questionnaire. Patients with at least two of the following signs were defined as having the syndrome: poor hearing with normal DPOAEs, vision not correctable to better than 20/30, or a MNSI score greater than 4. Findings: 29 participants met the case definition. CRP levels did not differ between groups but manganese, cobalt and tin levels were each greater in the cases than controls. No other environmental exposure differences were noted. Interpretation: Toenail manganese, cobalt, and tin levels were higher in those with the syndrome. These metals are potential neurotoxins suggesting a possible environmental origin for this unique and debilitating syndrome. Funding Statement: Hitchcock Foundation at the Dartmouth-Hitchcock Medical Center. Declaration of Interests: The authors have no financial or personal relationships that could inappropriately bias their work. Ethics Approval Statement: The research protocol was approved by the Committee for the Protection of Human Subjects of Dartmouth College and the Research Ethics Committee of Muhimbili University for Health and Allied Sciences. All participants gave written informed consent or parental consent and minor assent.

Limitation of Conventional Audiometry in Identifying Hidden Hearing Loss in Acute Noise Exposure.

PurposeThe concept of hidden hearing loss can explain the discrepancy between a listener's perception of hearing ability and hearing evaluation using pure tone audiograms. This study investigated the utility of the suprathreshold auditory brainstem response (ABR) for the evaluation of hidden hearing loss in noise-exposed ear with normal audiograms.Materials and MethodsA total of 15 patients (24 ears) with normal auditory thresholds and normal distortion product otoacoustic emissions were included in a retrospective analysis of medical records of 80 patients presenting with histories of acute noise exposure. The control group included 12 subjects (24 ears) with normal audiograms and no history of noise exposure. Pure tone audiometry and suprathreshold ABR testing at 90 dB peSPL were performed. The amplitudes and latencies of ABR waves I and V were compared between the noise-exposed and control groups.ResultsWe found no significant difference in the wave I or V amplitude, or the wave I/V ratio, between the two groups. The latencies of ABR wave I, V, and I-V interpeak interval were compared, and no significant intergroup difference was observed.ConclusionThe results suggest that either hidden hearing loss may not be significant in this cohort of patients with acute noise exposure history, or the possible damage by noise exposure is not reflected in the ABRs. Further studies are needed to inquire about the role of ABR in identification of hidden hearing loss.

Predictive Factors for the Success of Intratympanic Dexamethasone Treatment of Acute Subjective Tinnitus.

The purpose of this study was to determine the factors predicting the success or failure of intratympanic dexamethasone (ITD) injection in the treatment of acute subjective tinnitus (AST). We enrolled patients who were treated with ITD within 3 months of the onset of tinnitus, between 2013 and 2017. We compared the clinical characteristics and audiological data of the patients in the cured group (n=38, 45.6±13.3 years old) and the nonresponder group (n=40, 48.9±18.6 years old). The cured group was predominantly female (p=0.002). The mean duration of tinnitus before ITD was shorter in the cured group than the nonresponder group (p=0.002). The pure-tone averages in both sides were lower in the cured group than in the nonresponder group (p=0.018). The time of tinnitus awareness was shorter in the cured group than in the nonresponder group (p=0.014). Multivariable analysis showed that the duration of tinnitus (odds ratio [OR]=1.045), a history of exposure to noise just before tinnitus development (OR=7.766), and distortion product otoacoustic emissions results (OR=4.580) predicted the outcome of ITD treatment in AST. A short duration of tinnitus, no history of immediate noise exposure, and normal distortion product otoacoustic emissions could be favorable prognostic factors for AST treated with ITD injection.

Transplantation of human limbus–derived mesenchymal stromal cells via occipital approach improves hearing in animal auditory neuropathy

ObjectiveTo develop a surgical approach for cell transplantation into mouse cochlear nerves via an intracranial route and investigate whether transplantation of human limbus–derived mesenchymal stromal cells (HL-MSCs) can improve hearing in this model of auditory neuropathy. MethodsWe used 8-week-old CBA/CaJ male mice and created ouabain-induced auditory neuropathy. The surgical approach passed through the cerebellum to reveal the superior semicircular canal and brainstem, allowing access to the auditory nerve. Then HL-MSCs were injected around the cochlear nerve trunk using a micropipette driven by a micropump. Hearing thresholds in the mice were determined by auditory brainstem responses (ABRs) and distortion product otoacoustic emissions (DPOAEs). ResultsWe produced ouabain-induced neuropathy in mice with an elevated hearing threshold but normal DPOAE. Using immunohistological staining, we detected HL-MSCs were localized in the cochlear nerve trunk 2 days after cell transplantation via this occipital approach. More spiral ganglion neurons were detected in ouabain-treated cochleae 3 months after HL-MSCs transplantation compared to those without HL-MSCs transplantation. The ABR showed significant hearing improvement 3 months after HL-MSCs transplantation. ConclusionsWe successfully established a mouse model for cell transplantation into the intracranial cochlear nerve trunk and showed that HL-MSCs potentially can be applied as cell therapy to treat sensorineural hearing loss.

Tinnitus and Auditory Perception After a History of Noise Exposure: Relationship to Auditory Brainstem Response Measures.

To determine whether auditory brainstem response (ABR) wave I amplitude is associated with measures of auditory perception in young people with normal distortion product otoacoustic emissions (DPOAEs) and varying levels of noise exposure history. Tinnitus, loudness tolerance, and speech perception ability were measured in 31 young military Veterans and 43 non-Veterans (19 to 35 years of age) with normal pure-tone thresholds and DPOAEs. Speech perception was evaluated in quiet using Northwestern University Auditory Test (NU-6) word lists and in background noise using the words in noise (WIN) test. Loudness discomfort levels were measured using 1-, 3-, 4-, and 6-kHz pulsed pure tones. DPOAEs and ABRs were collected in each participant to assess outer hair cell and auditory nerve function. The probability of reporting tinnitus in this sample increased by a factor of 2.0 per 0.1 µV decrease in ABR wave I amplitude (95% Bayesian confidence interval, 1.1 to 5.0) for males and by a factor of 2.2 (95% confidence interval, 1.0 to 6.4) for females after adjusting for sex and DPOAE levels. Similar results were obtained in an alternate model adjusted for pure-tone thresholds in addition to sex and DPOAE levels. No apparent relationship was found between wave I amplitude and either loudness tolerance or speech perception in quiet or noise. Reduced ABR wave I amplitude was associated with an increased risk of tinnitus, even after adjusting for DPOAEs and sex. In contrast, wave III and V amplitudes had little effect on tinnitus risk. This suggests that changes in peripheral input at the level of the inner hair cell or auditory nerve may lead to increases in central gain that give rise to the perception of tinnitus. Although the extent of synaptopathy in the study participants cannot be measured directly, these findings are consistent with the prediction that tinnitus may be a perceptual consequence of cochlear synaptopathy.

A case of auditory neuropathy revealed by OTOF gene mutation analysis in a junior high school girl

ObjectiveCongenital auditory neuropathy (AN) affects hearing and speech development. The degree of hearing difficulty in congenital AN varies as a function of pathology at the inner ear hair cell (IHC) synapses or the auditory nerve. We report a case of a Chinese girl with AN revealed by OTOF (otoferlin) gene mutation analysis who had only a mild hearing loss. PatientA 13-year-old Chinese girl was diagnosed as having congenital AN on the basis of OTOF gene mutation analysis. She manifest a mild sensorineural hearing loss with 50% maximum monosyllable speech discrimination rate, normal DPOAEs (distortion product otoacoustic emissions) beyond ambient noise levels, only SPs (summating potentials) evoked during ECoG (electrocochleography) and absent ABRs (auditory evoked brainstem responses) bilaterally to clicks presented at 100 dBnHL. She was able to effectively communicate with others by speech reading owing to her mild hearing loss. Moreover, bilateral hearing aids helped her to communicate. ConclusionsOur patient was demonstrated to have a mutation on the OTOF gene. Nevertheless, she was able to communicate using auditory visual speech reading in spite of a mild auditory threshold elevation probably due to partial pathology at the IHC synapses or in the auditory nerve.

Loud Music Exposure and Cochlear Synaptopathy in Young Adults: Isolated Auditory Brainstem Response Effects but No Perceptual Consequences.

The purpose of this study was to test the hypothesis that listeners with frequent exposure to loud music exhibit deficits in suprathreshold auditory performance consistent with cochlear synaptopathy. Young adults with normal audiograms were recruited who either did (n = 31) or did not (n = 30) have a history of frequent attendance at loud music venues where the typical sound levels could be expected to result in temporary threshold shifts. A test battery was administered that comprised three sets of procedures: (a) electrophysiological tests including distortion product otoacoustic emissions, auditory brainstem responses, envelope following responses, and the acoustic change complex evoked by an interaural phase inversion; (b) psychoacoustic tests including temporal modulation detection, spectral modulation detection, and sensitivity to interaural phase; and (c) speech tests including filtered phoneme recognition and speech-in-noise recognition. The results demonstrated that a history of loud music exposure can lead to a profile of peripheral auditory function that is consistent with an interpretation of cochlear synaptopathy in humans, namely, modestly abnormal auditory brainstem response Wave I/Wave V ratios in the presence of normal distortion product otoacoustic emissions and normal audiometric thresholds. However, there were no other electrophysiological, psychophysical, or speech perception effects. The absence of any behavioral effects in suprathreshold sound processing indicated that, even if cochlear synaptopathy is a valid pathophysiological condition in humans, its perceptual sequelae are either too diffuse or too inconsequential to permit a simple differential diagnosis of hidden hearing loss.

Auditory nerve disease and auditory neuropathy spectrum disorders.

In 1996, a new type of bilateral hearing disorder was discerned and published almost simultaneously by Kaga et al. [1] and Starr et al. [2]. Although the pathophysiology of this disorder as reported by each author was essentially identical, Kaga used the term "auditory nerve disease" and Starr used the term "auditory neuropathy". Auditory neuropathy (AN) in adults is an acquired disorder characterized by mild-to-moderate pure-tone hearing loss, poor speech discrimination, and absence of the auditory brainstem response (ABR) all in the presence of normal cochlear outer hair cell function as indicated by normal distortion product otoacoustic emissions (DPOAEs) and evoked summating potentials (SPs) by electrocochleography (ECoG). A variety of processes and etiologies are thought to be involved in its pathophysiology including mutations of the OTOF and/or OPA1 genes. Most of the subsequent reports in the literature discuss the various auditory profiles of patients with AN [3,4] and in this report we present the profiles of an additional 17 cases of adult AN. Cochlear implants are useful for the reacquisition of hearing in adult AN although hearing aids are ineffective. In 2008, the new term of Auditory Neuropathy Spectrum Disorders (ANSD) was proposed by the Colorado Children's Hospital group following a comprehensive study of newborn hearing test results. When ABRs were absent and DPOAEs were present in particular cases during newborn screening they were classified as ANSD. In 2013, our group in the Tokyo Medical Center classified ANSD into three types by following changes in ABRs and DPOAEs over time with development. In Type I, there is normalization of hearing over time, Type II shows a change into profound hearing loss and Type III is true auditory neuropathy (AN). We emphasize that, in adults, ANSD is not the same as AN.

A case of cortical deafness and loss of vestibular and somatosensory sensations caused by cerebrovascular lesions in bilateral primary auditory cortices, auditory radiations, and postcentral gyruses – complete loss of hearing despite normal DPOAE and ABR

Conclusion: A right-handed 38-year-old man’s complete loss of hearing could be diagnosed as cortical deafness caused by cerebral vascular lesions in bilateral auditory cortices. Objective: The aim of this case report was to study the pathophysiology of a particular patient who manifested deafness without residual hearing and lost somatosensory sensation, vestibular sensation, and articulation ability after a right internal carotid-posterior communicating artery (IC-PC) aneurysm and subarachnoidal hemorrhage. Methods: MRI, aphasia and neurological tests, subjective and objective audiometry, and vestibular function tests were performed. Results: The neurological test revealed system loss of somatosensory sensation with normal motor function and articulation ability. Brain imaging revealed extensive infarction in the bilateral primary auditory cortices, postcentral gyruses, and the bilateral partial third frontal gyruses. Pure-tone audiometry of both ears revealed off-the-scale results and speech audiometry demonstrated 0% maximum speech discrimination. However, objective audiometry showed normal distortion product otoacoustic emissions (DPOAE) and normal auditory brainstem response (ABR). The patient showed 0% perception of environmental, speech, and music sounds in both ears. He was unable to feel vestibular sensation despite normal caloric nystagmus. He showed no damage to his larynx or articulation organs.

Synaptic transmission between end bulbs of Held and bushy cells in the cochlear nucleus of mice with a mutation in Otoferlin.

Mice that carry a mutation in a calcium binding domain of Otoferlin, the putative calcium sensor at hair cell synapses, have normal distortion product otoacoustic emissions (DPOAEs), but auditory brain stem responses (ABRs) are absent. In mutant mice mechanotransduction is normal but transmission of acoustic information to the auditory pathway is blocked even before the onset of hearing. The cross-sectional area of the auditory nerve of mutant mice is reduced by 54%, and the volume of ventral cochlear nuclei is reduced by 46% relative to hearing control mice. While the tonotopic organization was not detectably changed in mutant mice, the axons to end bulbs of Held and the end bulbs themselves were smaller. In mutant mice bushy cells in the anteroventral cochlear nucleus (aVCN) have the electrophysiological hallmarks of control cells. Spontaneous miniature excitatory postsynaptic currents (EPSCs) occur with similar frequencies and have similar shapes in deaf as in hearing animals, but they are 24% larger in deaf mice. Bushy cells in deaf mutant mice are contacted by ∼2.6 auditory nerve fibers compared with ∼2.0 in hearing control mice. Furthermore, each fiber delivers more synaptic current, on average 4.8 nA compared with 3.4 nA, in deaf versus hearing control mice. The quantal content of evoked EPSCs is not different between mutant and control mice; the increase in synaptic current delivered in mutant mice is accounted for by the increased response to the size of the quanta. Although responses to shocks presented at long intervals are larger in mutant mice, they depress more rapidly than in hearing control mice.

Clinical presentation and audiologic findings in pediatric auditory neuropathy

Aim: of the study was to rule out audiologic findings, related etiologies and its effect in pediatric patients having hearing deficits that are most likely due to a neuropathy of the eighth nerve. Study Design: Retrospective neo-natal hearing screening programme based. Subject and Methods: Subjects include 30 children aged from 0 yrs to 12 yrs, were tested with pure tone audiometry, behavioral observation audiometry, free-filed audiometry, speech audiometry, auditory brainstem response, and click evoked otoacoustic emissions. Results: Pure tone and free-field testing revealed 40 ears (66.67%, n = 60) with sloping type, sensorineural hearing loss, 20 ears (33.3%, n = 60) had flat configuration. Out of this 18 (6%, n = 30) subject showed bilateral similar configuration (either bilateral sloping type/ flat type of audiogram). Rest 12 (40%, n = 30) subject showed bilateral different pattern. 10 (33.3%, n = 30 children demonstrated fair to poor word discrimination scores and the other 2 (6.67%, n = 30) had fair to good word discrimination. For other rest of 18 (60%, n = 30) children speech test couldn't be performed because of age limit and poor speech and language development. Out of 30 subjects 28 (93.3%, n = 30) showed normal distortion product Otoacoustic emissions and 2(6.67%, n = 30) subjects showed absent emissions. Conclusions: All thirty children demonstrated absent or marked abnormalities of brainstem auditory evoked potentials which suggest cochlear outer hair cell function is normal; mostly lesion is located at the eighth nerve or beyond. Generally auditory neuropathy is associated with different etiologies and it is difficult to diagnose auditory neuropathy with single audiological test; sufficient test of battery is required for complete assessment and diagnosis of auditory neuropathy

Auditory Brainstem Response and Distortion‐Product Otoacoustic Emission Studies in Neonates at High‐Risk for Hearing Loss

Objectives: 1) Recognize that preterm infants less than 1300g have a well-described and markedly increased incidence of hearing loss, possibly attributed to reversible early middle ear pathology. 2) Analyze if distortion product oto-acoustic emissions (DPOAE) and/or auditory brainstem response (ABR) could be useful adjuncts when used in addition to tympanometry and otoendoscopy in evaluation of neonatal hearing and middle ear. Methods: Institutional review board approved prospective study at a tertiary care center neonatal intensive care unit with subjects undergoing ABR, DPAOE, tympanometry, and otoendoscopy studies within 72 hours of birth and in scheduled increments until discharge. From January 2010 to date, 77 neonates have been examined. Results: Our results confirmed that DPOAE could be a reliable and repetitive study from 24 weeks of gestational age and onward. When comparing traditional tympanometry to DPOAE, 85.7% of examinations with type B or C tympanometry also had an abnormal DPOAE result. Conversely, 62.5% of patients with type A tympanometry had a normal DPOAE result. Furthermore, in patients with a clinical diagnosis of AOM or OME, 66.7% percent had an abnormal DPAOE result. Regarding ABR threshold studies, there were several limitations with data acquisition due to incubator interference and background noise; thus, the potential of ABR in this population remains to be determined. Conclusions: This study suggests that DPOAE can be used as a reliable hearing evaluation in the neonatal population. Additionally, it may serve as a useful adjunct and insight into evaluating neonatal middle ear pathology, especially when combined with tympanometry and otoendoscopy.

Evaluation of the Protective Effect of Beta Glucan on Amikacin Ototoxicity Using Distortion Product Otoacoustic Emission Measurements in Rats

ObjectivesThis experimental study investigated the possible protective effect of beta glucans on amikacin ototoxicity.MethodsThirty-eight rats with normal distortion product otoacoustic emissions (DPOAEs) were divided into four groups. Group K was the control group. Group A was injected intramuscularly (i.m.) with amikacin 600 mg/kg/day between days 1-15. Group AB was given beta glucan gavage 1 mg/kg/day on days 0-15 and given amikacin 600 mg/kg/day i.m. on days 1-15. Group B was administered only beta glucan gavage, 1 mg/kg/day, on days 0-15. The DPOAEs were elicited in different frequency regions between 2,003 and 9,515 Hz, as distortion product diagrams (DPgrams), before and after the medication was administered, in all groups, on days 1, 5, 10, and 15.ResultsNo significant changes in the DPgrams were observed in group K. In group A, significant deterioration was observed at the 8,003 and 9,515 Hz frequencies on day 10, and at the 3,991, 4,557, 5,660, 6,726, 8,003, and 9,515 Hz frequencies on day 15. For group AB, statistically significant deterioration was observed at the 2,824, 8,003, and 9,515 Hz frequencies on day 15. The results for group B showed a significant improvement of hearing at the 2,378, 2,824, 3,363, and 3,991 Hz frequencies on day 1, at the 3,363, 3,991, and 8,003 Hz frequencies on day 10, and at the 8,003 Hz frequency on day 15.ConclusionThis study suggests that amikacin-induced hearing loss in rats may be limited to some extent by concomitant use of beta glucan.

Reversible Long-Term Changes in Auditory Processing in Mature Auditory Cortex in the Absence of Hearing Loss Induced by Passive, Moderate-Level Sound Exposure

It has become increasingly clear that even occasional exposure to loud sounds in occupational or recreational settings can cause irreversible damage to the hair cells of the cochlea and the auditory nerve fibers, even if the resulting partial loss of hearing sensitivity, usually accompanied by tinnitus, disappears within hours or days of the exposure. Such exposure may explain at least some cases of poor speech intelligibility in noise in the face of a normal or near-normal audiogram. Recent findings from our laboratory suggest that long-term changes to auditory brain function-potentially leading to problems with speech intelligibility-can be effected by persistent, passive exposure to more moderate levels of noise (in the 70 dB SPL range) in the apparent absence of damage to the auditory periphery (as reflected in normal distortion product otoacoustic emissions and auditory brainstem responses). Specifically, passive exposure of adult cats to moderate levels of band-pass-filtered noise, or to band-limited ensembles of dense, random tone pips, can lead to a profound decrease of neural activity in the auditory cortex roughly in the exposure frequency range, and to an increase of activity outside that range. This can progress to an apparent reorganization of the cortical tonotopic map, which is reminiscent of the reorganization resulting from hearing loss restricted to a part of the hearing frequency range, although again, no hearing loss was apparent after our moderate-level sound exposure. Here, we review this work focusing specifically on the potential hearing problems that may arise despite a normally functioning auditory periphery.

小児突発難聴の臨床像についての検討

Sudden sensorineural hearing loss is usually unilateral, and the cause is not identified in most adult cases. However, a specific cause has frequently been found in the case of children, in whom idiopathic sudden sensorineural hearing loss (ISHL) is comparatively rare. We investigated 20 cases of acute unilateral sensorineural hearing loss in children associated with a certain disease, but which was first diagnosed as ISHL. Thirteen patients aged 6 to 16 years old were diagnosed as having psychogenic (functional) hearing loss. Discrepancies in behavioral and objective tests are most valuable when functional hearing loss is suspected. Elevated pure-tone thresholds associated with normal distortion product otoacoustic emissions (DPOAEs) enable prompt further investigation. There are several conditions that may mimic functional hearing loss, so auditory brainstem response (ABR) testing is necessary to verify the actual cause. The unilateral profound hearing loss in 2 patients aged 7 and 11 years old was due to asymptomatic mumps proven by detecting the mumps IgM antibody. Total hearing recovery in the 125-1000 Hz frequencies occurred in one case. In 5 patients aged 6 to 12 years old with acute hearing loss and vertigo, high resolution CT imaging showed an abnormally enlarged vestibular aqueduct on the affected side. Large vestibular aqueduct syndrome should be considered in acute high-frequency sloping hearing loss with an A-B gap at low frequencies.

Audiology characteristics in newborns and infants who failed in the hearing screening by transiently evoked otoacoustic emissions: 89 cases study

The present study was to evaluate the audiological characteristics of infants with normal auditory brainstem response thresholds in click and abnormal transiently evoked otoacoustic emissions. Relationships between test results of distortion product otoacoustic emissions (DPOAE) and other hearing testing methods were also evaluated. The participants consisted of eighty-nine infants, with a total of 123 ears. All participants' TEOAE screening results were abnormal but diagnostic click ABR results were normal. The participants were classified into the following groups based on the test results from distortion product otoacoustic emissions: group A (normal all-frequency), group B (abnormal low-frequency), group C (abnormal high-frequency), and group D (abnormal all-frequency). Obtained from these groups were compared to results of other hearing tests including the latency of ABR wave I, 40 Hz auditory event related potential (40 Hz AERP), 226 Hz and 1000 Hz tympanometry, and acoustic reflex. Results In six hearing tests in the 123 ears, seven ears (5.7%) were normal, while 116 ears (94.3%) were abnormal. No significantly differences were detected between boys (93.9%) and girls (95.1%), as well as between left (93.1%) and right ears (95.4%). The proportion of abnormal test results ranked as follows: 59 ears in group D (48.0%), 34 ears in group B (27.6%), 20 ears in group A (16.3%), and 10 ears in group C (8.2%). The highest abnormal rates in groups A, B and D were acoustic reflex, which were 40.0% for group A, 55.9% for group B and 66.1% for group D respectively. The highest abnormal rate in group C was the latency of ABR wave I (50.0%). Distribution of low-frequency hearing loss in each group was mainly mild. However, one ear in group B was moderate hearing loss, six ears in group D were moderate hearing loss, and one ear in group D was severe hearing loss. The present study showed that, of which infants with normal thresholds of ABR failed the hearing screening, comprehensively audiology assessment is needed. And of which infants with normal DPOAE in full frequency or abnormal in high frequency region or low frequency region need to be followed up.

The Association of Lead Exposure and Impairment of Brainstem Auditory-evoked Response and Cochlea Function

PP-31-156 Background/Aims: On the basis of some researches, the heavy metals (including lead, mercury, and tin) may be toxic on hearing in human beings and animals. Complex exposures to lead and noise were the 2 common sources of occupational exposures in the factories. The aim of the study was to investigate the effect of occupational lead on the auditory system. Methods: We measured the auditory brainstem-evoked response and cochlea function with distortion product otoacoustic emissions (DPOAEs) that are preneural responses of the outer hair cells of the inner ear in 12 adult lead-workers and 12 age- and sex- matched persons who were not exposed to lead and noise. Results: The results showed that the auditory brainstem-evoked response latency of wave I, II, III, and III–V significantly increased in the group of lead-workers (blood lead: 36.13 ± 4.52 μg/dL), as compared with the group without lead exposure (blood lead: 4.09 ± 1.41 μg/dL). The latency of wave I, II, III, V, and interpeak latency I–III were correlated to blood lead levels. Mean DPOAEs of the lead workers were significantly different from the reference group at DP frequencies of 812, 1000, 1281, 1593, 2031, 2562, and 3187 Hz. However, the DPOAEs for the lead workers were within the normal ranges of the reference group only at 4031 Hz. Although there was a tendency for the lead workers to have diminished DPOAEs, no consistent correlation of DPOAEs with lead level was found. The prevalence of normal DPOAEs in the lead workers was up to 79%. Conclusion: We concluded that lead should be otoneural toxic, especially, in the workers exposed to lead and noise both. The hearing conservation program should enhance more for the worker exposing to both ototoxic agents.

Effects of Negative Middle Ear Pressure on Distortion Product Otoacoustic Emissions and Application of a Compensation Procedure in Humans

This study was intended to systematically examine the effect of negative middle ear pressure (MEP) on distortion product otoacoustic emissions (DPOAEs) and to validate a compensation procedure to account for negative MEP encountered in DPOAE measurement. In experiment 1, the 2f1 - f2 DPOAE was measured for nine f2 frequencies from 600 to 8000 Hz in 16 adults under three MEP conditions: normal MEP, negative MEP, and compensated MEP. The subjects' voluntarily induced negative MEPs, with magnitudes ranging from -40 to -420 daPa, were measured tympanometrically with the tympanometric peak pressure. Each negative MEP was then compensated for by applying an equivalent amount of negative air pressure into the ear canal. The three MEP conditions were compared in terms of difference in DPOAE level. Experiment 2 was conducted to measure the DPOAE under normal and negative MEP conditions by using a different system with a higher frequency resolution in 19 subjects. Negative MEP generally attenuated DPOAEs more for low frequencies than for high frequencies. For the frequencies of 1000 Hz and below, the mean DPOAE level was reduced by at least 4 to 6 dB for negative MEPs lower than -100 daPa (i.e., less negative). Reduction of the DPOAE level increased with increasing negative MEP (e.g., 10 to 12 dB for -160 daPa and higher, i.e., more negative). For f2 = 2000, 4000, and 6000 Hz, the effect of negative MEP was not significant. For 3000 Hz, DPOAE-level reduction was significant (e.g., 5 dB for MEP = -70 to -95 daPa and up to 12 dB for -290 to -420 daPa). As a result, a peak at 2000 Hz and a notch at 3000 Hz appeared in the DPOAE change versus frequency function. For 8000 Hz, DPOAE levels tended to increase in high negative MEPs, although the changes were not significant. Intersubject variability in the effect of negative MEP on DPOAEs was large. As the negative MEPs were compensated for, the decreased DPOAE levels were significantly corrected. DPOAEs measured with higher resolution in experiment 2 verified the frequency-specific effects of negative MEPs. Results revealed that the peak and notch in the DPOAE change versus frequency function shifted toward higher frequencies when negative MEP was increased, and a second peak emerged at a higher frequency. Negative MEP substantially decreases DPOAE level for low frequencies and some mid-frequencies but tends to increase DPOAE level for high frequencies. Results suggest that any degree of negative MEP should be corrected to obtain an accurate outcome of DPOAE measurement. The MEP compensation procedure is effective in restoring normal DPOAEs in ears with negative MEPs. Examining changes in DPOAE level under negative MEP allows for further study of the transmission of acoustic signals through an altered middle ear system. A minimal change of DPOAE level at 2000 Hz indicates that the primary resonant frequency of the middle ear is lower than 2000 Hz. The variation in DPOAE change in the middle to high frequency range implies multiple resonances of the middle ear system.