Distortion Product Otoacoustic Emissions Responses Research Articles

Cochlear Function in Individuals with and without Spontaneous Otoacoustic Emissions.

This study investigated the status of spontaneous otoacoustic emissions (SOAEs) on cochlear function in a cohort of male/female participants with a wide age range. It examined whether there was a correlation between the presence of SOAEs and measurements of transient evoked otoacoustic emissions (TEOAEs), distortion product otoacoustic emissions (DPOAEs), SOAEs and extended high-frequency (EHF) hearing thresholds. 463 participants (222 male, 241 female; age range 20-59 years) with pure-tone thresholds ≤25 dB HL for octave frequencies of 500-8000 Hz were included in the study, divided into three age groups (20-29, 30-39, and 40-59 years). Evaluations included EHF (9000-16,000 Hz) hearing thresholds and TEOAE, DPOAE and SOAE measures. Multiple regression models showed that participants with SOAEs had larger expected amplitudes and signal-to-noise ratios (SNRs) for TEOAE and DPOAE responses than participants without SOAEs, holding gender and age variables constant. Spearman correlation tests identified deterioration in TEOAE and DPOAE amplitudes and SNRs, and EHF hearing thresholds with age in participants without SOAEs. Among participants with SOAEs, no significant decreases in TEOAE and DPOAE measures were shown in participants with older age. Nonetheless, as expected, EHF hearing thresholds did become worse with age, with or without SOAEs. Participants with identifiable SOAEs had greater TEOAE and DPOAE amplitudes and SNRs than participants without SOAEs. SOAEs appear to be a useful marker of cochlear health in adults.

Generation of distortion product otoacoustic emissions in infants with a combined air and bone conduction stimulus.

Evaluation of Distortion Product Otoacoustic Emissions (DPOAEs) by combining Air Conduction (AC) and Bone Conduction (BC) stimuli in infants. Measurements were performed in 19 normal hearing infants, and in 23 adults serving as a control group. The stimulus consisted either of two AC tones, or of combined AC/BC tones. DPOAEs were measured for f2 at 0.7, 1, 2, 4kHz, and a constant ratio of f2/f1=1.22. Sound pressure level of the primary stimulus L1 was held constant at 70dB SPL, while the level of L2 was decreased in 10dB steps from 70 to 40dB SPL. A response was included for further analysis when DPOAEs reached a Signal to Noise Ratio (SNR) of ≥6dB. Additional DPOAE responses of <6dB SNR were included when visual inspection of the measurements indicated clear DPOAEs. DPOAEs could be elicited in infants at 2 and 4kHz for the AC/BC stimulus. DPOAE amplitudes evoked by the AC/AC stimulus were larger than those by the AC/BC stimulus, with the exception of 1kHz. The highest amplitudes of DPOAEs were registered for a stimulation level of L1=L2=70dB, with the exception of AC/AC at 1kHz, where the highest amplitudes were with L1-L2=10dB. We demonstrated that DPOAEs can be generated in infants by a combined AC/BC stimulus at 2 and 4kHz. The high noise floor needs to be further reduced to achieve more valid measurements in frequencies <2kHz.

Otological Features of Patients with Musculocontractural Ehlers-Danlos Syndrome Caused by Pathogenic Variants in CHST14 (mcEDS-CHST14).

Musculocontractural Ehlers-Danlos syndrome (EDS) caused by pathogenic variants in CHST14 (mcEDS-CHST14) is a subtype of EDS characterized by multisystem malformations and progressive fragility-related manifestations. A recent international collaborative study showed that 55% of mcEDS-CHST14 patients had hearing loss (HL), more commonly of the high-frequency type. Here, we report the first systemic investigation of the otological features of patients with this disorder based on the world's largest cohort at Shinshu University Hospital. Nine patients [18 ears; four male and five female patients; mean age, 18 years old (range, 10-28)] underwent comprehensive otological evaluation: audiogram, distortion product otoacoustic emission (DPOAE) test, and tympanometry. The audiogram, available in all 18 ears, showed HL in eight patients (8/9, 89%) and in 14 ears (14/18, 78%): bilateral in six patients (6/9, 67%) and unilateral in two (2/9, 22%); mild in eight ears (8/18, 44%) and moderate in six (6/18, 33%); and high-frequency HL in five (5/18, 28%) and low-frequency HL in five (5/18, 28%). An air-bone gap was detected in one ear (1/18, 6%). DPOAE was available in 13 ears, with the presence of a response in five (5/13, 38%) and the absence in eight (8/13, 62%), including in three ears of normal hearing. Tympanometry results were available in 12 ears: Ad type in nine (9/12, 75%) and As type in one (1/12, 8.3%). Patients with mcEDS-CHST14 had a high prevalence of HL, typically sensorineural and bilateral, with mild to moderate severity, of high-frequency or low-frequency type, and sometimes with no DPOAE response. The pathophysiology underlying HL might be complex, presumably related to alterations of the tectorial membrane and/or the basilar membrane of Corti associated with disorganized collagen fibril networks. Regular and careful check-ups of hearing using multiple modalities are recommended for mcEDS-CHST14 patients.

Impact of endolymphatic hydrops on DPOAE in subjects with normal to mild hearing loss.

The increased endolymph volume affects a shift in the organ of Corti and basilar membrane in ears with endolymphatic hydrops (EH), which might affect distortion-product otoacoustic emissions (DPOAE) by altering the operating point of the outer hair cells. We investigated how changes in DPOAE are related to the distribution site of EH. Prospective study. Among 403 patients with hearing or vestibular symptoms who underwent contrast-enhanced magnetic resonance imaging (MRI) for the diagnosis of EH and subsequent DPOAE testing, subjects whose hearing levels on pure tone audiometry were ≤35dB at all frequencies were included in this study. In patients with EH on MRI, the presence and amplitude of DPOAE were evaluated between groups with hearing levels of ≤25dB at all frequencies versus hearing levels of >25dB at one or more frequencies. There were no differences in the distribution of EH between groups. The amplitude of DPOAE had no clear correlation with the presence of EH. However, in both groups, there was a significantly higher probability of the presence of a DPOAE response from 1001 to 6006Hz in cases with EH in the cochlea. Among patients whose hearing levels were ≤35dB at all frequencies, better responses on DPOAE testing were found in subjects with EH in the cochlea. Alteration of DPOAEs in the early stages of hearing impairment could indicate morphological changes in the inner ear with altered basilar membrane compliance due to EH. 4.

The comprehensive audiological evaluation in young violinists: the medial olivocochlear system, high frequency thresholds, and the auditory figure ground test.

The aim of this study was to examine whether the medial olivocochlear hearing system functions, the high frequency hearing thresholds and speech discrimination in noise performance can guide us in assessing the risk of hearing loss among violinists. It is aimed to investigate possible hearing damage that is not reflected in pure tone hearing thresholds in violinists. The participants (n = 50) who have normal hearing and the ages of 18-30 were included in this study in two groups: violinists and controls who are unrelated to music. High frequency audiometer, auditory figure ground test (AFG) for speech discrimination in noise performance, Distortion Product Otoacoustic Emission (DPOAE) and contralateral suppression on DPOAE for medial olivocochlear system function tests were applied to all participants as well as routine audiological tests. The high frequency hearing thresholds were obtained higher in violinists compared to the controls. In violinists, the AFG test scores and the suppression amount at 1kHz were lower than the controls. In addition, DPOAE responses at 4-6kHz were obtained lower in violinists (p < 0.05). The reason for high frequency hearing loss, decreased DPOAE response amplitudes, and poor medial olivocochlear function in violinists can be explained by the long-term exposure to high-level noise caused by the violin, one of the closest musical instruments. Routine and comprehensive audiological follow-up is crucial for musicians.

Audiological Features in 63 Patients With Cochlear Nerve Deficiency.

We aimed to investigate the clinical features of cochlear nerve deficiency (CND), and in particular, the long-term course of hearing disability and audiogram shapes. Retrospective observational nonrandomized group study. Academic medical center. The subjects were 63 children with congenital hearing loss who visited our hospital between 2009 and 2019 and underwent MRI, based on which they were diagnosed with CND. There were 61 cases of unilateral CND and two cases of bilateral CND. Imaging tests by MRI and CT and audiometric assessments by pure-tone audiometry and distortion product otoacoustic emission were performed. Among the cases of CND diagnosed by assessing the cochlear nerve on MRI, approximately 20% of the bony cochlear nerve canals that could be assessed on CT were normal. Of the 61 cases diagnosed with unilateral CND, 55 cases had cochlear nerve aplasia (90.2%), and six had cochlear nerve hypoplasia (9.8%), with a mean hearing ability of 92.2 and 94.6 dB HL, respectively. Thus, the majority of cases had severe-to-profound hearing loss. The overall audiometric patterns were 78.7% flat, 9.8% cookie-bite, and 9.8% high-frequency. Six of 61 cases (9.8%) had a distortion product otoacoustic emission (DPOAE) response based on the affected side, and none of the cases lost the response during follow-up. Herein, we report the largest study on CND and performed CND image and audiometric assessments. Accurately in diagnosing CND requires not only CT but also MRI assessment. Hearing loss is often severe to profound; however, various audiometric patterns have been observed. CND includes a small number of cases that respond to DPOAE, indicating that some CND cases are clinically diagnosed with auditory neuropathy spectrum disorder (ANSD). A sustained DPOAE response might help in differentiating CND from other ANSDs. Children with congenital deafness who have passed the newborn hearing screening by DPOAE should be examined by MRI to rule out CND.

Effect of Korean Red Ginseng on Noise-Induced Hearing Loss.

Objective:Noise-induced hearing loss (NIHL) is one of the most important problems affecting both social and professional life of patients. There is no treatment method considered to be successful on the hearing loss that has become a permanent nature. Aim of this study is to evaluate protective effect of Korean Red Ginseng (KRG) against NIHL in an animal model.Methods:Twenty-eight rats were separated into four groups [control saline (group I), control KRG (group II), saline + noise (group III), KRG + noise (group IV)]. Rats in the saline and KRG groups were fed via oral gavage with a dose of 200 mg/kg/day throughout for 10 days. Fourteen rats (group III and IV) were exposed to 4 kHz octave band noise at 120 dB SPL for 5 hours. Hearing levels of rats were evaluated by distortion product otoacoustic emissions (DPOAE) and auditory brainstem responses (ABR) at 4, 8, 12, 16 and 32 kHz frequencies prior to and on days 1, 7 and 10 after the noise exposure. Rats were sacrificed on 10th day, after the last audiological test. Cochlea and spiral ganglion tissues were evaluated by light microscopy.Results:Audiological and histological results demonstrated that after noise the group IV showed better results than group III. In the noise exposed groups, the most prominent damage was seen at the 8 kHz frequency region than other regions. After the noise exposure, DPOAE responses were lost in 1st, 7th and 10th measurements in both group III and IV. Thus, we were not able to perform any statistical analyses for DPOAE results.Conclusion:Our findings suggest that KRG seems to be an efficient agent against NIHL. There is need for additional research to find out about the mechanisms of KRG’s protective effect.

Central and peripheral auditory abnormalities in chinchilla animal model of blast-injury

Exposure to blast overpressure or high-intensity sound can cause injuries to the auditory system, which leads to hearing loss or tinnitus. In this study, we examined the involvement of peripheral auditory system (PAS), and central auditory system (CAS) changes after exposure to blast overpressure (15-25 psi) on Day 1 and additionally during 7 days of post blast time period in chinchillas. Auditory brainstem response (ABR), distortion product otoacoustic emission (DPOAE), and cochlear hair cell changes were measured or identified in post-blast period within 7 days to detect injuries in the PAS. In the CAS, changes in NMDAR1 (excitatory receptor) and GABAA (inhibitory receptor) as well as changes in serotonin (5-HT2A) and acetylcholine (AChR) receptors were examined in different brain regions: auditory cortex (AC), geniculate body (GB), inferior colliculus (IC) and amygdala by immunofluorescence staining. We observed the PAS abnormalities of increased ABR threshold and decreased DPOAE response in animals after blast exposure with hearing protection devices (e.g., earplug). Blast exposure also caused a reduction in both NMDAR1 and GABAA receptor levels in acute condition (post-blast or Day 1) in AC and IC, while serotonin and acetylcholine receptor levels displayed a biphasic response at Day 1 and Day 7 post-exposure. Results demonstrate that the earplug can protect the tympanic membrane and middle ear against structural damage, but the hearing level, cochlear outer hair cell, and the central auditory system (levels of excitatory and inhibitory neurotransmitter receptors) were only partially protected at the tested blast overpressure level. The findings in this study indicate that blast exposure can cause both peripheral and central auditory dysfunctions, and the central auditory response is independent of peripheral auditory damage. The CAS dysfunction is likely mediated by direct transmission of shockwaves in all the regions of central nervous system (CNS), including nerves and surrounding tissues along the auditory pathways. Hence, targeting central auditory neurotransmitter abnormalities may have a therapeutic benefit to attenuate blast-induced hearing loss and tinnitus.

The most informative otoacoustic emission indicators for prognostication the course and solving expert issues in the participants of the joint forces operation with combat acutrauma

Introduction: Registration of otoacoustic emission is the general objective method in diagnostics of receptor defeats of the auditory system, first of all the organ of Corti outer hair cells. At an acutrauma the receptive field of auditory system suffers. The purpose: to determine the possible prognostic criteria of progression of perceptual hearing disorders according to distortion-product otoacoustic emission (DPOAE) in servicemen who received acutrauma in real combat conditions. Material and methods: In the this work indicators for distortion-product otoacoustic emission (DPOAE) in servicemen who received acutrauma in the area of the joint forces operation have been investigated. We had examined 2 groups of people: 1st group – 30 persons who had shown improvement in auditory function and general condition after treatment, 2nd group – 30 persons in whom disease progression had observed, they had no positive dynamics after treatment. The investigation of otoacoustic emission (OAE) was conducted by analyzing system “Eclipse” of the “Interacoustics” Company (Denmark). Was used the generally accepted methodology. The recording has performed in the frequency band (1 - 6) kHz. Results. The complete adequate response of OAE across the entire frequency spectrum has been registered in only one patient with combat acutrauma from group 1. In most of the surveyed patients in whom the OAE was registered, a partially positive test was obtained as already mentioned. The response was considered as registered when the signal-to-noise ratio exceeded or was equal to 3 dB. The decision on a partially positive test was made when only one or more of the tested frequency bands had an adequate response. A positive response was registered in 42.6% of fighters of group 1 and 31.25% of group 2. According to our data, in patients of group 1 in 57.4% of cases the DPOAE was not registered at any of the frequencies, the same situation in patients of group 2 were in 68.75%. Thus in group 1 positive, including in part, the DPOAE was recorded at one frequency in 16.7% of cases, at twо frequencies - at 18.5%, at three frequencies - 7.4% and at four frequencies -1 . 8%. In group 2, a positive test was registered at one frequency in 16.7% of cases, at twо frequencies - 4.2% at three frequencies - 6.2%. At four frequencies, a positive test (complete response) was not registered in any patient of group 2. We analyzed at which frequencies the response was most often recorded with partially positive DPOAE results in surveyed patients. The corresponding percentages were calculated from the total number of received responses. At the same time, in patients of group 1 partial response of DPOAE have been registered more often than in group 2. In group 1, DPOAE was recorded at frequencies of 1 kHz in 52.2% of cases, 2 kHz - 34.8%, 4 kHz - 78.3%, 6 kHz - 21.7%. In persons from group 2, with a progressive course of sensorineural hearing loss, the DPOAE response was observed at frequencies of 1 kHz - 38.5%, 2 kHz - 46.1%, 4 kHz - 53.8%, 6 kHz - 23.1%. Thus, in both groups, the DPOAE response have been most often recorded at 4 kHz: (78.3%) and (53.8%), respectively. It is followed by the frequency of registration in 1 group with a frequency of 1 kHz (52.2%), and in group 2 with 2 kHz (46.1%). Thus, registration of the DPOAE will promote objectification of sensorineural hearing loss course at a combat acutrauma. Conclusions: The conducted researches have shown the importance of DPOAE definition at patients with a combat acutrauma that promotes timely and objective detection of receptor structures defeats of the auditory system at such patients. The results of DPOAE registration can be used to predict the course of sensorineural hearing loss and assess adverse factors in combat acutrauma. Complete absence of registration of DPOAE at servicemen with a combat acutrauma can serve as an objective sign of prognostically unfavorable course of sensorineural hearing loss at such patients.

Evaluation of Efferent Auditory System and Hearing Quality in Parkinson's Disease: Is the Difficulty in Speech Understanding in Complex Listening Conditions Related to Neural Degeneration or Aging?

Purpose The effects of neurological diseases on the auditory system have been a notable issue for investigators because the auditory pathway is closely associated with neural systems. The purposes of this study are to evaluate the efferent auditory system function and hearing quality in Parkinson's disease (PD) and to compare the findings with age-matched individuals without PD to present a perspective on aging. Method The study included 35 individuals with PD (mean age of 48.50 ± 8.00 years) and 35 normal-hearing peers (mean age of 49 ± 10 years). The following tests were administered for all participants: the first section of the Speech, Spatial and Qualities of Hearing Scale; pure-tone audiometry, speech audiometry, tympanometry, and acoustic reflexes; and distortion product otoacoustic emissions (DPOAEs) and contralateral suppression of DPOAEs. SPSS Version 25 was used for statistical analyses, and values of p < .05 were considered statistically significant. Results There were no statistically significant differences in the pure-tone audiometry thresholds and DPOAE responses between the individuals with PD and their normal-hearing peers (p = .732). However, statistically significant differences were found between the groups in suppression levels of DPOAEs and hearing quality (p < .05). In addition, a statistically significant and positive correlation was found between the amount of suppression at some frequencies and the Speech, Spatial and Qualities of Hearing Scale scores. Conclusions This study indicates that medial olivocochlear efferent system function and the hearing quality of individuals with PD were affected adversely due to the results of PD pathophysiology on the hearing system. For optimal intervention and follow-up, tasks related to hearing quality in daily life can also be added to therapies for PD.

Auditory Performance in Recovered SARS-COV-2 Patients.

Objective:While COVID-19 symptoms impact rhinology (anosmia) and laryngology (airways), two major disciplines of the otolaryngology armamentarium, the virus has seemed to spare the auditory system. A recent study, however, reported changes in otoacoustic emission (OAE) signals measured in SARS-COV-2 positive patients. We sought to assess the effect of COVID-19 infection on auditory performance in a cohort of recovered SARS-COV-2 patients and controls. To avoid a potential bias of previous audiological dysfunction not related to SARS-COV-2 infection, the study encompasses patients with normal auditory history. We hypothesized that if SARS-COV-2 infection predisposes to hearing loss, we would observe subtle and early audiometric deficits in our cohort in the form of subclinical auditory changes.Study Design:Cross-sectional study.Setting:Tertiary referral center.Patients:The Institutional Review Board approved the study and we recruited participants who had been positive for SARS-COV-2 infection, according to an Reverse Transcription Polymerase Chain Reaction (RT-PCR) test on two nasopharyngeal swabs. The patients included in this study were asymptomatic for the SARS-COV-2 infection and were evaluated following recovery, confirmed by repeated swab testing. The control group comprised healthy individuals matched for age and sex, and with a normal auditory and otologic history.Intervention(s):The eligibility to participate in this study included a normal audiogram, no previous auditory symptoms, normal otoscopy examination with an intact tympanic membrane, and bilateral tympanometry type A. None of our volunteers reported any new auditory symptoms following SARS-COV-2 infection. Ototacoustic emissions (OAE) and auditory brainstem response (ABR) measurements were used to evaluate the auditory function.Main Outcome Measure(s):OAE and ABR measurements.Results:We have found no significant differences between recovered asymptomatic SARS-COV-2 patients and controls in any of transitory evoked otoacoustic emission (TEOAE), distortion product otoacoustic emissions (DPOAE), or ABR responses.Conclusions:There is no cochlear dysfunction represented by ABR, TEOAE, and DPOAE responses in recovered COVID-19 asymptomatic patients. Retrocochlear function was also preserved as evident by the ABR responses. A long-term evaluation of a larger cohort of SARS-COV-2 patients will help to identify a possible contribution of SARS-COV-2 infection to recently published anecdotal auditory symptoms associated with COVID-19.

Interpreting auditory brainstem evoked responses and distortion product otoacoustic emissions in diabetic patients with normal hearing

ObjectiveHearing impairment is a reported late complication of diabetes mellitus (DM). Previous studies have suggested that microangiopathic complications may cause cochlear nerve function deterioration. We evaluated the auditory brainstem evoked responses (ABRs) and distortion product otoacoustic emission (DPOAE) results according to the presence of DM in subjects with normal hearing. MethodsA cross-sectional comparative study was conducted from January 2016 to January 2018. Auditory function tests including ABR and DPOAE were performed for outpatients complaining of unilateral tinnitus. All of analyses were conducted in ears without tinnitus on contralateral side of tinnitus ears. We included subjects showing hearing thresholds within 25 dB at 0.5, 1k, 2k, and 4k on pure tone audiometry. 45 ears in patients with type 2 diabetes mellitus and 85 ears in non-diabetic patients were finally enrolled in our study. ResultsDiabetic subjects showed significantly more prolonged absolute peak latencies (I, III, V) and inter-peak latencies (I–V, III–V) than non-diabetic subjects. However, there was no significant difference in the inter-peak latency (I–III) between these two groups. Diabetic subjects also showed significantly lower amplitudes at f2 frequencies of 1001, 1200, 1587, 4004, 5042, and 6348 Hz than non-diabetic subjects. Additionally, the prevalence of a DPOAE response, defined as 3 dB above the noise floor, was significantly lower in diabetic subjects than that in non-diabetic subjects. ConclusionDiabetic patients with normal hearing can still have abnormal ABR and DPOAE results due to diabetic neuroangiopathy. ABR and DPOAE assessments can help in detecting subclinical auditory dysfunction, which precedes the manifestation of hearing impairment in diabetic patients.

Assessment of Hidden Hearing Loss in Normal Hearing Individuals with and Without Tinnitus.

To evaluate the functions of cochlear structures and the distal part of auditory nerve as well as dead regions within the cochlea in individuals with normal hearing with or without tinnitus by using electrophysiological tests. Nine individuals (ages: 21-59 years) with normal hearing with tinnitus were included in the study group. Thirteen individuals (ages: 25-60 years) with normal hearing without tinnitus were included in the control group. Immitancemetric examination, pure-tone audiometry (125Hz-16kHz), speech audiometry in quiet and noise environments, transient evoked otoacoustic emissions (TEOAEs), distortion product otoacoustic emissions (DPOAEs), threshold equalizing noise (TEN test (500Hz-4kHz), and ECochG tests, Beck Depression Questionnaire, Tinnitus Handicap Questionnaire, and Visual Analog Scale were performed. In the study group, three patients were found to have a minimal depression and six were found to have a mild depression. In pure-tone audiometry, the threshold (6-16 kHz) in the study group was significantly higher than that of the control group at all frequencies. In the study group, lower performance scores were obtained in speech discrimination in noise in both ears. In the control group, no dead region was detected in the TEN test whereas 75% of subjects in the study group had dead regions. DPOAE and TEOAE responses between study and control group subjects were not different. In the ECochG test, subjects in the study group showed an increase in the summating potential/action potential (SP/AP) ratio in both ears. Determination of the SP/AP ratio in patients with tinnitus may be useful in diagnosing hidden hearing loss. Detection of dead regions in 75% of patients in the TEN test may indicate that inner hair cells may be responsible for tinnitus.

Otoacoustic emissions in neonates exposed to smoke during pregnancy

IntroductionThe toxic substances present in cigarette smoke can damage cochlea hair cells. This effect has been investigated by measuring otoacoustic emissions. ObjectiveTo investigate the impact of stimuli on otoacoustic emissions, comparing neonates with and without exposure to cigarette smoke during pregnancy. MethodsTransient-evoked otoacoustic emissions, evoked by a click stimulus, and distortion product otoacoustic emissions, evoked by two tones tests were conducted in both ears, using an Interacoustic TITAN device. The study included 105 neonates divided into two groups: a study group, comprising 47 neonates exposed to smoke during pregnancy; and a control group comprized of 58 neonates who were not exposed. All participants had normal neonatal hearing screening. ResultsNo statistical differences in distortion product otoacoustic emissions response levels were found between the groups. In the transient-evoked otoacoustic emissions tests lower response levels were observed in the study group than the control group in frequency band analysis of the right ear, with statistically significant differences in signals and signal-noise ratio (except at 1kHz). ConclusionThe impact of smoking exposure could be analyzed through transient-evoked otoacoustic emissions in neonates. The group effect of smoke exposure during pregnancy was evidenced by a reduction in transient-evoked otoacoustic emissions levels. This same effect was not observed for the analyses performed on distortion product otoacoustic emissions levels.

Subclinical cochlear dysfunction in newly diagnosed relapsing-remitting multiple sclerosis

BackgroundHearing impairment in multiple sclerosis has long been considered a process mainly related to the central auditory system. However, increasing evidence also suggests a peripheral involvement of the inner ear. The objective of this study was to investigate subclinical cochlear dysfunction and possible correlation with disease severity in untreated newly diagnosed multiple sclerosis patients using transient-evoked and distortion-product otoacoustic emissions. MethodsForty patients with newly diagnosed relapsing-remitting multiple sclerosis, clinically normal hearing and no brainstem lesions (study group) and forty matched controls (control group) were included in the study. All subjects had a routine audiological evaluation including history and clinical examination, pure tone audiometry, acoustic immittance test, auditory brainstem response and otoacoustic emissions recording. Self-administered questionnaires were used to evaluate self-perception of hearing disability. ResultsAuditory brainstem response and pure tone audiometry thresholds resulted within normal range in all patients. The amplitudes of transient-evoked and distortion-product otoacoustic emissions responses were significantly reduced at 1000, 1500, 2000 and 3000 Hz in the study group compared to the control group. ConclusionsThis study shows decreased otoacoustic emission amplitudes in untreated multiple sclerosis patients with clinically normal hearing and no brainstem demyelinating plaques, suggesting a subclinical cochlear impairment. This alteration may represent an early sign of peripheral hearing damage, suggesting a role for otoacoustic emissions in the early diagnosis of cochlear dysfunction in multiple sclerosis patients. However, given that otoacoustic emissions primarily reflects cochlear function, and that the wave I of the auditory brainstem responses was spared, the evidence supporting a peripheral involvement of acoustic pathways due to multiple sclerosis can only be hypothetically attributed to an early subclinical involvement of outer hair cells.

Universal neonatal hearing screening in a tertiary care center in South India

Objective: The aim of the study is to determine the prevalence of hearing loss among newborn infants and to assess the effectiveness and utility of otoacoustic emission (OAE) as a screening tool to detect hearing impairment in newborns and the relationship between selected risk factors and hearing loss. Study Design: This study involved 3121 newborns delivered in a tertiary care center over a 3-year period, who were subjected to distortion product OAE (DPOAE) within 24–72 h of life; failed candidates underwent repeat DPOAE after 30 days. Infants failed the second DPOAE test and then underwent DPOAE and brain stem-evoked response audiometry (BERA) at 3 months of life. Results: 20.95% newborns failed the first screening test, 11.77% failed the second test, and 61.91% of these infants failed the third OAE test. Of the 26 infants who failed the third test, 15 had abnormal results on BERA. Overall, the prevalence of hearing loss was 0.48%. Conclusion: Implementation of a national universal newborn hearing screening program in India is the need of the hour, as early detection of hearing loss will aid early rehabilitation and better outcomes.

Modeling the dependence of the distortion product otoacoustic emission response on primary frequency ratio.

When measured as a function of primary frequency ratio r = f2/f1, using a constant f2, distortion product otoacoustic emission (DPOAE) response demonstrates a bandpass shape, previously interpreted as the evidence for a cochlear "second filter." In this study, an alternate, interference-based explanation, previously advanced in variants, is forwarded on the basis of experimental data along with numerical and analytical solutions of nonlinear and linear cochlear models. The decrease of the DPOAE response with increasing and decreasing ratios is explained by a diminishing "overlap" generation region and the onset of negative interference among wavelets of different phase, respectively. In this paper, the additional quantitative hypothesis is made that negative interference becomes the dominant effect when the spatial width of the generation (overlap) region exceeds half a wavelength of the DPOAE wavelets. Therefore, r is predicted to be optimal when this condition is matched. Additionally, the minimum on the low-ratio side of the DPOAE curve is predicted to occur as the overlap region width equals one wavelength. As the width of the overlap region depends on both tuning and ratio, while wavelength depends on tuning only, an experimental method for estimating tuning from either the width of the pass band or the optimal ratio of the DPOAE vs. ratio curve has been theoretically formulated and evaluated using numerical simulations. A linear model without the possibility of nonlinear suppression is shown to reasonably approximate data from human subjects at low ratios reinforcing the relevance of the proposed negative interference effect. The different dependence of the distortion and reflection DPOAE components on r as well as the nonmonotonic behavior of the distortion component observed at very low ratios are also in agreement with this interpretation.

ABO Blood Group and Cochlear Status: Otoacoustic Emission Markers.

There are an increasing number of research studies examining the effects of ABO blood group on susceptibility to disease. However, little is known regarding the potential relationship between blood group and hearing. Higher risk of noise-induced hearing loss was linked to blood group O in several occupational health studies. Based on this finding, a recent study of cochlear status was conducted with normal-hearing female participants representing equal numbers of the four blood groups in the ABO blood group system. ABO blood group was associated with cochlear characteristics, including the prevalence of spontaneous otoacoustic emissions (SOAEs) and the amplitudes of transient-evoked otoacoustic emissions (TEOAEs) and distortion-product otoacoustic emissions (DPOAEs). Females with blood group O showed significantly lower amplitudes of DPOAEs at some frequencies and lower prevalence of SOAEs compared with participants with blood group B. There was a general trend of reduced TEOAE and DPOAE amplitudes in blood group O individuals compared with participants with non-O blood groups. Following from this finding, and based on known sex differences in otoacoustic emission characteristics, the present study examined the possible effects of blood group on otoacoustic emission status in males. Sixty clinically normal-hearing males aged between 18 and 26 years, with equal numbers of participants in each of the ABO blood groups, were recruited by purposive sampling. SOAE, DPOAE, and linear and nonlinear TEOAE recordings were collected from all participants, as well as tympanometric data related to external and middle ear characteristics. The male blood group O participants exhibited significantly lower SOAE prevalence and reduced amplitudes of DPOAEs on average, and in the midfrequency range, than participants with blood group B, and lower nonlinear and linear TEOAE amplitudes at a number of frequencies when compared with participants with blood groups A and B. A consistent trend of lower TEOAE and DPOAE response amplitudes was observed in participants with blood group O. No significant difference was noted among blood groups for outer or middle ear characteristics. These results were consistent with previous findings of reduced otoacoustic emission responses in female blood group O individuals. Results support the hypothesis that blood group O individuals may be at increased risk of cochlear damage from noise exposure. Further investigation on the potential link between ABO blood group and auditory status, including potentially differential effects of noise exposure on cochlear function, is needed. The possible effects of ABO blood group on other aspects of audition, such as hearing sensitivity, speech understanding, and auditory processing, should be evaluated.

Probing Apical-Basal Differences in the Human Cochlea Using Distortion-Product Otoacoustic Emission Phase.

Distortion-product otoacoustic emission (DPOAE) phase is shaped by interaction between the evoking stimulus waves. Near-invariant at high frequencies, DPOAE phase-vs-frequency functions measured at fixed ratios bend into sloping functions at low frequencies. The different phase behaviors observed suggest that the mechanics underlying the generation of OAEs differ in the halves of the cochlea. To map out the phenomenological extent of low-to-mid frequency phase bends, this study recorded DPOAE responses from 20 normal-hearing human adult ears for a wide range of stimulus frequencies, f1 and f2, where f2 frequency sweeps from 0.25 to 8 kHz, and the f2/ f1 ratio varies from 1.05 to 1.49. Our preliminary results show two transitions in the phase slopes. One near 2.6 kHz in agreement with the literature, and another of opposite polarity near 0.75 kHz which has not been reported before. We find that the f2 frequencies marking these defining phase features are invariant with stimulus ratio. Even as the underlying mechanics remain unknown, the invariance opens the door for DPOAE phase to reliably characterize apical-basal differences across age groups and species.

Otoacoustic Emissions in Young Children with Autism.

The aim of this study is to investigate otoacoustic emissions (OAEs) in young children with autism compared with those in an age-matched control group. Thirty-eight children with autism aged 3-6 years and 27 typically developing (normally developing) control subjects participated in this study. All the participants had normal hearing and middle-ear function. Auditory brainstem responses were used to determine the hearing status in the autism group. Transient-evoked otoacoustic emissions (TEOAEs) and distortion-product otoacoustic emissions (DPOAEs) were measured in the two groups. The TEOAE response level was higher in the autism group. Analysis of the DPOAE response showed that the mean emission levels at 1.5, 2 , 3, and 6 kHz and signal/noise ratios at 2, 4, 6, and 8 kHz were higher in the autism group (p<0.05). The greatest between-group differences were observed in the DPOAE signal levels at 2, 3, and 6 kHz (p=0.000). No statistically significant difference was found between the noise levels in the autism and control groups (p>0.05). The emission responses in the autism group were higher than those in the control group. The increase in DPOAEs at high frequencies may be related to the higher outer cell activation in the autism group. Further studies with larger sample sizes comprising younger children are needed to confirm the result and investigate the possible association between the increased OAEs and auditory sensitivity reported in autism.