Contralateral Suppression of Transient Evoked Otoacoustic Emissions: Normative Data for a Clinical Test Set-Up

Standardization of the TEOAE Contralateral Suppression Test in Terms of Stimulus Intensity and Contralateral Noise Duration in Individuals with Normal Hearing

BACKGROUND

 A standard method and parameter study were performed for the contralateral suppression test.

PURPOSE

 Our study aimed to determine the contralateral transient-evoked otoacoustic emission (TEOAE) suppression test method and stimulus-noise parameters that have a standard procedure and will enable the efferent system to be easily evaluated in clinics.

RESEARCH DESIGN

 This study was conducted in two parts with two different groups of participants as a within-subjects design. In the first part, the signal-to-noise ratio at which maximum suppression obtained was investigated with 29 participants. In the second part, the optimal contralateral noise presentation method (in terms of noise-time or noise-sweep) was examined with 21 participants.

STUDY SAMPLE

 In the first part 29 young adults aged between 18 and 32 (23.03 ± 2.84), 20 females and 9 males, and in the second part 21 young adults aged between 19 and 34 years (mean age: 23.71 ± 3.48 years), 16 females and 5 males, participated in the second part. All participants had normal hearing.

DATA COLLECTION AND ANALYSIS

 To obtain maximum OAE suppression, different parameters were tested with the Otodynamics ILO292-II OAE device at both parts of the study in a double-walled audiometric test booths. Multirepeated analysis of variance, pairwise comparison, Friedman test, and Wilcoxon signed-rank tests were used for statistical analysis.

RESULTS

 In the first part, maximum suppression was achieved at 65 dB peSPL (decibel peak-equivalent sound pressure level) TEOAE stimulus and 65 dB SPL broadband noise. In the second part, maximum suppression was obtained in noise-time method with 30 seconds "duration."

CONCLUSIONS

 To provide standardization in clinics, it can be recommended that the contralateral suppression of OAEs was measured at 65 dB peSPL TEOAE stimulus and 65 dB SPL broadband noise in the linear stimulation mode with Otodynamics ILO 292-II double-probe OAE device. To obtain maximum suppression, the noise-time method with 30 seconds duration can be used.

Contralateral noise effects on otoacoustic emissions and electrophysiologic responses in normal-hearing adults

Contralateral noise inhibits the amplitudes of cochlear and neural responses. These measures may hold potential diagnostic utility. The medial olivocochlear (MOC) reflex underlies the inhibition of cochlear responses but the extent to which it contributes to inhibition of neural responses remains unclear. Mertes and Leek [J. Acoust. Soc. Am. 140, 2027-2038 (2016)] recently examined contralateral inhibition of cochlear responses [transient-evoked otoacoustic emissions (TEOAEs)] and neural responses [auditory steady-state responses (ASSRs)] in humans and found that the two measures were not correlated, but potential confounds of older age and hearing loss were present. The current study controlled for these confounds by examining a group of young, normal-hearing adults. Additionally, measurements of the auditory brainstem response (ABR) were obtained. Responses were elicited using clicks with and without contralateral broadband noise. Changes in TEOAE and ASSR magnitude as well as ABR wave V latency were examined. Results indicated that contralateral inhibition of ASSRs was significantly larger than that of TEOAEs and that the two measures were uncorrelated. Additionally, there was no significant change in wave V latency. Results suggest that further work is needed to understand the mechanism underlying contralateral inhibition of the ASSR.

Medial olivary complex reflex in term newborns with hyperbilirubinemia

OBJECTIVE

This study aimed to compare the integrity of the efferent auditory pathways of newborns that had high hyperbilirubinemia levels and required treatment due to these and healthy newborns.

METHODS

Term-born (37 weeks or later) infants that were brought to the Newborn Polyclinic of the Başkent University Hospital were included in the study. The study included a total of 84 infants including healthy newborns (n = 42) and those that had jaundice and were receiving phototherapy (n = 42). After conducting a general otorhinolaryngology examination on all newborns included in the study, Transient Otoacoustic Emission (TEOAE) test was carried out in the absence and presence of contralateral noise. The obtained contralateral suppression values were compared between the two groups.

RESULTS

In the TEOAE test, the responses obtained at 1 kHz in the newborns receiving phototherapy were found to be lower. The difference between the groups was significant (p = 0.038). The rates of suppression presence at 2 kHz, 2.8 kHz and total OAE were found significantly higher (p < 0.05) in the group not receiving phototherapy. Among the phototherapy-receiving infants, the hyperbilirubinemia levels of the infants in whom suppression was obtained in the contralateral suppression test did not show a statistically significant difference in comparison to those in whom suppression was not obtained (p > 0.05).

CONCLUSION

Based on the obtained data, hyperbilirubinemia may have a disruptive effect on the efferent auditory system in newborns. Consequently, we are of the opinion that, in addition to hearing screening in risky newborn infants, a MOC suppression test would be useful.

Short-Term Reliability of Different Methods of Contralateral Suppression of Transient Evoked Otoacoustic Emission in Children and Adults

Purpose This study aimed to investigate the reliability of 3 methods to measure contralateral suppression of transient evoked otoacoustic emissions (TEOAEs) in children and adults. Method Contralateral suppression of TEOAEs was measured in 14 adults and 14 children using 3 methods with and without contralateral acoustic stimulus (CAS). Method-I having "2 s on-off" and Method-II having "10 s on-off" interleaved presentation of white noise. Method-III used "continuous presentation of white noise". Test-retest reliability was checked in adults without removing the probe (same-probe recording) and reinserting the probe (different-probe recording) and in children using a different-probe recording. Results The absolute suppression amplitude of TEOAEs was higher for "continuous noise," followed by "10 s on-off" and "2 s on-off" CAS. There was no significant effect of age across the 2 probe recordings, 3 methods of TEOAEs with and without CAS, and for the absolute suppression amplitude. Also, in adults, there was no significant difference between same-probe and different-probe recordings across the 3 methods. High internal consistency was observed on Cronbach's alpha (α > .9) for the 3 methods and 2 probe recordings. High agreement and correlation between the recordings for all 3 methods were seen using Bland-Altman plots and Pearson product-moment correlation coefficient. Conclusion The study demonstrated that highly reliable contralateral suppression of TEOAE can be measured using the 3 methods in adults and children. However, continuous presentation of CAS resulted in greater TEOAE suppression amplitude compared to interleaved presentation of CAS; hence, the former is recommended.

Olivocochlear Efferent Activity Is Associated With the Slope of the Psychometric Function of Speech Recognition in Noise

OBJECTIVES

The medial olivocochlear (MOC) efferent system can modify cochlear function to improve sound detection in noise, but its role in speech perception in noise is unclear. The purpose of this study was to determine the association between MOC efferent activity and performance on two speech-in-noise tasks at two signal-to-noise ratios (SNRs). It was hypothesized that efferent activity would be more strongly correlated with performance at the more challenging SNR, relative to performance at the less challenging SNR.

DESIGN

Sixteen adults aged 35 to 73 years participated. Subjects had pure-tone averages ≤25 dB HL and normal middle ear function. High-frequency pure-tone averages were computed across 3000 to 8000 Hz and ranged from 6.3 to 48.8 dB HL. Efferent activity was assessed using contralateral suppression of transient-evoked otoacoustic emissions (TEOAEs) measured in right ears, and MOC activation was achieved by presenting broadband noise to left ears. Contralateral suppression was expressed as the decibel change in TEOAE magnitude obtained with versus without the presence of the broadband noise. TEOAE responses were also examined for middle ear muscle reflex activation and synchronous spontaneous otoacoustic emissions (SSOAEs). Speech-in-noise perception was assessed using the closed-set coordinate response measure word recognition task and the open-set Institute of Electrical and Electronics Engineers sentence task. Speech and noise were presented to right ears at two SNRs. Performance on each task was scored as percent correct. Associations between contralateral suppression and speech-in-noise performance were quantified using partial rank correlational analyses, controlling for the variables age and high-frequency pure-tone average.

RESULTS

One subject was excluded due to probable middle ear muscle reflex activation. Subjects showed a wide range of contralateral suppression values, consistent with previous reports. Three subjects with SSOAEs had similar contralateral suppression results as subjects without SSOAEs. The magnitude of contralateral suppression was not significantly correlated with speech-in-noise performance on either task at a single SNR (p > 0.05), contrary to hypothesis. However, contralateral suppression was significantly correlated with the slope of the psychometric function, computed as the difference between performance levels at the two SNRs divided by 3 (decibel difference between the 2 SNRs) for the coordinate response measure task (partial rs = 0.59; p = 0.04) and for the Institute of Electrical and Electronics Engineers task (partial rs = 0.60; p = 0.03).

CONCLUSIONS

In a group of primarily older adults with normal hearing or mild hearing loss, olivocochlear efferent activity assessed using contralateral suppression of TEOAEs was not associated with speech-in-noise performance at a single SNR. However, auditory efferent activity appears to be associated with the slope of the psychometric function for both a word and sentence recognition task in noise. Results suggest that individuals with stronger MOC efferent activity tend to be more responsive to changes in SNR, where small increases in SNR result in better speech-in-noise performance relative to individuals with weaker MOC efferent activity. Additionally, the results suggest that the slope of the psychometric function may be a more useful metric than performance at a single SNR when examining the relationship between speech recognition in noise and MOC efferent activity.

Olivocochlear efferent contributions to speech-in-noise recognition across signal-to-noise ratios

The medial olivocochlear (MOC) efferent system modifies cochlear output to aid signal detection in noise, but the precise role of efferents in speech-in-noise understanding remains unclear. The current study examined the contribution of the MOC reflex for speech recognition in noise in 30 normal-hearing young adults (27 females, mean age = 22.7 yr). The MOC reflex was assessed using contralateral inhibition of transient-evoked otoacoustic emissions. Speech-in-noise perception was evaluated using the coordinate response measure presented in ipsilateral speech-shaped noise at signal-to-noise ratios (SNRs) ranging from -12 to 0 dB. Performance was assessed without and with the presence of contralateral noise to activate the MOC reflex. Performance was significantly better with contralateral noise only at the lowest SNR. There was a trend of better performance with increasing contralateral inhibition at the lowest SNR. Threshold of the psychometric function was significantly correlated with contralateral inhibition. Response time on the speech task was not significantly correlated with contralateral inhibition. Results suggest that the MOC reflex contributes to listening in low SNRs and the relationship between the MOC reflex and perception is highly dependent upon the task characteristics.

Does Contralateral Inhibition of Transient Evoked Otoacoustic Emissions Suggest Sex or Ear Laterality Effects?

PURPOSE

The purpose of this study was to examine contralateral inhibition of transient evoked otoacoustic emissions (TEOAEs) in young adults with normal hearing as a function of ear and sex.

METHOD

Young female (n = 50) and male (n = 50) adults with normal hearing participated. TEOAEs were measured bilaterally with 80 dB peSPL nonlinear clicks and 60 dB peSPL linear clicks with and without a contralateral broadband noise elicitor at 65 dB SPL. Absolute TEOAE inhibition and normalized TEOAE inhibition (i.e., percentage of inhibition) were examined.

RESULTS

With both 80 and 60 dB peSPL evoking stimuli, there were significant main effects of ear and sex (p < .05). TEOAE levels were larger in women and in the right ear. There were no statistically significant main effects of ear and sex on absolute TEOAE inhibition (p > .05). Significant main effects of ear and sex were, however, found with normalized TEOAE inhibition (p < .05; greater in men and in the left ear). Statistically significant negative correlations and significant linear predictive relations were found between TEOAE levels and normalized TEOAE inhibitions in both ears (p < .001). There is no evidence of the same with absolute inhibition of TEOAEs (p > .05).

CONCLUSIONS

If one considers that efferent inhibition of TEOAEs is an absolute quantity, the significant effect of ear and sex on normalized inhibition and the negative association and linear predictive relationship between TEOAE level and inhibition can be viewed as spurious effects. As such, contralateral inhibition of TEOAEs does not suggest sex or ear laterality effects.

Tinnitus, Medial Olivocochlear System, and Music Exposure in Adolescents

INTRODUCTION

The most common cause of tinnitus is the exposure to noise; in the case of adolescents, music is the main sound source they are exposed to. Currently, one of the hypotheses about the genesis of tinnitus is related to the deterioration in the functioning of the medial olivocochlear system (MOCS).

AIM

The aim of this study was to determine the presence or absence of tinnitus in adolescents with normal hearing and to relate it to: (a) the functioning of the MOCS, by the contralateral suppression of the transient evoked otoacoustic emissions (TEOAEs) and (b) the musical general exposure (MGE).

MATERIALS AND METHODS

A cross-sectional descriptive correlational study was conducted. The sample was composed by adolescents with ages between 14 and 15. Two questionnaires were administered, one in relation to the subjective report of tinnitus and the other in relation to recreational activities to know the MGE.

RESULTS

The results showed that the amplitude of frequencies (1000, 1500, 2000, and 3000 Hz) and global amplitude of TEOAEs, with and without acoustic contralateral stimulation, were higher in the group without tinnitus, with a statistically significant difference (P < 0.05). The suppressive effect was higher in the group without tinnitus; however, there was no statistically significant difference. Contrastingly, a significant association (P < 0.05) between exposure to music and tinnitus was observed; 72.41% of the adolescents with high exposure to music had tinnitus.

DISCUSSION AND CONCLUSION

The results of the present investigation provide a contribution to the hypothesis of "the participation of the MOCS." Furthermore, a high MGE can be considered a risk factor for the onset of tinnitus.

Concurrent measures of contralateral suppression of transient-evoked otoacoustic emissions and of auditory steady-state responses

Contralateral suppression of otoacoustic emissions (OAEs) is frequently used to assess the medial olivocochlear (MOC) efferent system, and may have clinical utility. However, OAEs are weak or absent in hearing-impaired ears, so little is known about MOC function in the presence of hearing loss. A potential alternative measure is contralateral suppression of the auditory steady-state response (ASSR) because ASSRs are measurable in many hearing-impaired ears. This study compared contralateral suppression of both transient-evoked otoacoustic emissions (TEOAEs) and ASSRs in a group of ten primarily older adults with either normal hearing or mild sensorineural hearing loss. Responses were elicited using 75-dB peak sound pressure level clicks. The MOC was activated using contralateral broadband noise at 60 dB sound pressure level. Measurements were made concurrently to ensure a consistent attentional state between the two measures. The magnitude of contralateral suppression of ASSRs was significantly larger than contralateral suppression of TEOAEs. Both measures usually exhibited high test-retest reliability within a session. However, there was no significant correlation between the magnitude of contralateral suppression of TEOAEs and of ASSRs. Further work is needed to understand the role of the MOC in contralateral suppression of ASSRs.

Efeito de supressão das emissões otoacústicas em lactentes termo e pré-termo

RESUMO Objetivo Verificar a ocorrência e a magnitude do efeito de supressão das emissões otoacústicas evocadas por estímulo transiente, em lactentes a termo e pré-termo, estabelecendo-se níveis de referência para utilização clínica. Método A amostra foi composta por 40 lactentes, de 5 dias a 4 meses de idade, sem risco para alteração neurológica e auditiva e com emissões otoacústicas presentes ao nascimento, sendo 20 nascidos a termo e 20 nascidos pré-termo que permaneceram mais de cinco dias em Unidade de Terapia Intensiva Neonatal. O clique linear foi apresentado a 65 decibels Nível de Pressão Sonora, em blocos de 15 segundos sem ruído e com ruído contralateral, a 60 decibels Nível de Pressão Sonora. Considerou-se presença de supressão quando houve redução da resposta na presença de ruído. Os valores médios de supressão foram estabelecidos e a comparação entre os grupos foi analisada estatisticamente. Resultados A supressão ocorreu em 100% das crianças e não variou em função do lado da orelha e entre os grupos. Conclusão Todas as crianças apresentaram supressão, independente do grupo. A supressão média obtida na população total foi de 0,85 decibel. O critério de referência mínimo recomendado para utilização clínica foi a redução de 0,20 decibel na resposta geral.

The Hyperactivity of Efferent Auditory System in Patients with Schizophrenia: A Transient Evoked Otoacoustic Emissions Study

OBJECTIVE

Electrophysiological studies, which are mostly focused on afferent pathway, have proven that auditory processing deficits exist in patients with schizophrenia. Nevertheless, reports on the suppressive effect of efferent auditory pathway on cochlear outer hair cells among schizophrenia patients are limited. The present, case-control, study examined the contralateral suppression of transient evoked otoacoustic emissions (TEOAEs) in patients with schizophrenia.

METHODS

Participants were twenty-three healthy controls and sixteen schizophrenia patients with normal hearing, middle ear and cochlear outer hair cells function. Absolute non-linear and linear TEOAEs were measured in both ears by delivering clicks stimuli at 80 dB SPL and 60 dB SPL respectively. Subsequently, contralateral suppression was determined by subtracting the absolute TEOAEs response obtained at 60 dBpe SPL during the absence and presence of contralateral white noise delivered at 65 dB HL. No attention tasks were conducted during measurements.

RESULTS

We found no significant difference in absolute TEOAEs responses at 80 dB SPL, in either diagnosis or ear groups (p>0.05). However, the overall contralateral suppression was significantly larger in schizophrenia patients (p<0.05). Specifically, patients with schizophrenia demonstrated significantly increased right ear contralateral suppression compared to healthy control (p<0.05).

CONCLUSION

The present findings suggest increased inhibitory effect of efferent auditory pathway especially on the right cochlear outer hair cells. Further studies to investigate increased suppressive effects are crucial to expand the current understanding of auditory hallucination mechanisms in schizophrenia patients.

Reliability of measures of transient evoked otoacoustic emissions with contralateral suppression

The reliability of measures of transient evoked otoacoustic emissions (TEOAEs) with contralateral suppression was examined. The effect of test session (i.e., initial test; retest without probe removal; retest with probe removal; and retest 1-2 days post initial test), gender, and ear was examined in 14 young adult females and 14 young adult males. TEOAEs were obtained bilaterally with 60 dB peSPL linear click stimuli with and without a contralateral 65 dB SPL broadband noise suppressor. Absolute TEOAE suppression and a normalized index of TEOAE suppression (i.e., percentage of suppression) were examined. Reliability of these measures was assessed with repeated measures linear mixed model analysis of variance, a coefficient of reliability, and Bland-Altman analyses. There were no statistically significant (p>0.05) main effects of test, gender, and ear or interactions for both absolute dB and % TEOAE suppression values. Cronbach's α were greater than 0.90 across the four tests for both TEOAE measures. Mean test differences or bias (i.e., between the initial and subsequent tests) for absolute and % TEOAE suppression ranged from -0.05 to 0.11 dB and -1.5% to 1.1%, respectively. There was no proportional/systematic bias with the mean differences of the first and subsequent measurements. Data herein were consistent with the view that bilateral TEOAE suppression measures are reliable across test sessions of 1-2 days among females and males and may provide a method to monitor medial olivocochlear efferent reflex status over time.

A study of cochlear and auditory pathways in patients with tension-type headache

Background

The purpose of this study was to systematically evaluate the function of cochlear and auditory pathways in patients suffering from tension-type headache (TTH) using various audiological methods.

Methods

Twenty-three TTH patients (46 ears) and 26 healthy controls (52 ears) were included, and routine diagnostic audiometry, extended high-frequency audiometry, acoustic reflex (ASR), transient evoked otoacoustic emissions (TEOAEs), distortion product otoacoustic emissions (DPOAEs) and suppression TEOAEs were tested.

Results

The TTH group showed higher thresholds (P < 0.05) for both pure tone and extended high-frequency audiometry at all frequencies except for 9, 14 and 16 kHz. All ASR thresholds were significantly higher (P < 0.05) in the TTH group compared with the controls, except for the ipsilateral reflex at 1 kHz, but the threshold differences between the ASR and the corresponding pure tone audiometry did not differ (P > 0.05). For the DPOAEs, the detected rates were lower (P < 0.05) in the TTH group compared with the controls at 4 and 6 kHz, and the amplitudes and signal to noise ratio (S/N) were not significantly different between groups. No differences in the TEOAEs (P > 0.05) were observed for the detected rates, amplitudes, S/Ns or contralateral suppression, except for the S/Ns of the 0.5-1 kHz TEOAE responses, which were significantly higher (P < 0.05) in the TTH group.

Conclusions

The results of our study indicate that subclinical changes in cochlear function are associated with TTH.

Efferent inhibition of otoacoustic emissions in preterm neonates

INTRODUCTION

Abnormalities in auditory function of newborns may occur not only because of preterm birth, but also from the use of medications and from diseases related to prematurity.

OBJECTIVE

To analyze the inhibitory effect from stimulation of the olivocochlear efferent system on transient evoked otoacoustic emissions in preterm neonates, comparing these data with those from full-term neonates.

METHODS

This was a prospective, cross-sectional, contemporary cohort study with 125 neonates, pooled into two groups: full-term (72 full-term neonates, 36 females and 36 males, born at 37-41 weeks of gestational age); and preterm (53 neonates, 28 males and 25 females, born at ≤36 weeks of gestational age, evaluated at the corrected gestational age of 37-41 weeks). Otoacoustic emissions were recorded using linear and nonlinear click-evoked stimuli, with and without contralateral stimulation.

RESULTS

The inhibitory effect of the efferent pathway in otoacoustic emissions was different (p=0.012) between groups, and a mean reduction of 1.48dB SPL in full-term births and of 1.02dB SPL in preterm births was observed for the non-linear click-evoked stimulus.

CONCLUSION

The results suggest a reduced inhibitory effect of the olivocochlear efferent system on otoacoustic emissions in preterm neonates.

Efferent inhibitory effect observed in otoacoustic emissions and auditory brainstem response in the neonatal population

OBJECTIVE

To characterize the inhibitory effect (IE) in the otoacoustic emission (OAE) and auditory brainstem response (ABR) in newborns at high and low risk for hearing loss.

DESIGN

Cross-sectional study.

PATIENTS AND METHODS

Seventy-nine newborns at low risk for hearing loss and 46 at high risk underwent transient evoked OAE (TEOAE), distortion product OAE (DPOAE) and ABR testing with or without the presence of contralateral white noise presented at a level of 60 dB SPL.

RESULTS

For both low- and high-risk newborns, there were no significant differences in IE between the left and right ears. There was a statistically significant difference in the right-ear IE between the low- and high-risk group for DPOAE and ABR testing. There was also greater agreement of the efferent system evaluation outcomes between TEOAE and ABR.

CONCLUSIONS

ABR testing detected IE in a greater number of newborns in the low-risk, as compared to the high-risk group.

Medial olivocochlear-induced transient-evoked otoacoustic emission amplitude shifts in individual subjects

Activation of the medial olivocochlear reflex (MOCR) can be assessed indirectly using transient-evoked otoacoustic emissions (TEOAEs). The change in TEOAE amplitudes when the MOCR is activated (medial olivocochlear (MOC) shift) has most often been quantified as the mean value in groups of subjects. The usefulness of MOC shift measurements may be increased by the ability to quantify significant shifts in individuals. This study used statistical resampling to quantify significant MOC shifts in 16 subjects. TEOAEs were obtained using transient stimuli containing energy from 1 to 10 kHz. A nonlinear paradigm was used to extract TEOAEs. Transient stimuli were presented at 30 dB sensation level (SL) with suppressor stimuli presented 12 dB higher. Contralateral white noise, used to activate the MOCR, was presented at 30 dB SL and was interleaved on and off in 30-s intervals during a 7-min recording period. Confounding factors of middle ear muscle reflex and slow amplitude drifts were accounted for. TEOAEs were analyzed in 11 1/3-octave frequency bands. The statistical significance of each individual MOC shift was determined using a bootstrap procedure. The minimum detectable MOC shifts ranged from 0.10 to 3.25 dB and were highly dependent on signal-to-noise ratio at each frequency. Subjects exhibited a wide range of magnitudes of significant MOC shifts in the 1.0-3.2-kHz region (median = 1.94 dB, range = 0.34-6.51 dB). There was considerable overlap between the magnitudes of significant and nonsignificant shifts. While most subjects had significant MOC shifts in one or more frequency bands below 4 kHz, few had significant shifts in all of these bands. Above 4 kHz, few significant shifts were seen, but this may have been due to lower signal-to-noise ratios. The specific frequency bands containing significant shifts were variable across individuals. Further work is needed to determine the clinical usefulness of examining MOC shifts in individuals.

The role of the medial olivocochlear system in the complaints of understanding speech in noisy environments by individuals with normal hearing

OBJECTIVE

The aim of our study is to investigate the relationship between the complaint of speech understanding in noisy environments and the findings of contralateral suppression of transient evoked otoacoustic emissions and speech recognition in noise test methods in individuals with normal hearing.

METHODS

Sixty-nine subjects between 18 and 53 years of age with normal hearing participated in the present study. The subjects were assigned to one of two groups, reported difficulty understanding speech in noise or no reported difficulty understanding speech in noise. After hearing and immitancemetric evaluation, contralateral suppression of transient evoked otoacoustic emissions and speech recognition in noise tests were administered to both groups. Suppression was calculated in half-octave frequency bands centered at 1.0, 1.5, 2.0, 3.0 and 4.0kHz.

RESULTS

We found out that the speech recognition in noise scores and contralateral suppression values were lower in subjects with the complaint of speech understanding in noise than those who do not have such complaints.

CONCLUSIONS

We concluded that the complaint of speech understanding in noise may be related to the medial efferent system dysfunction, so central auditory nervous system.

Wavelet analysis demonstrates no abnormality in contralateral suppression of otoacoustic emissions in tinnitus patients

The efferent auditory system is thought to play a role in the origin of tinnitus. Part of this system can be tested in humans with contralateral suppression of otoacoustic emissions. Stimulation of the medial olivocochlear efferent system is responsible for this reduction of otoacoustic emissions after contralateral acoustic stimulation. Previous research on patients with tinnitus showed inconclusive results. With wavelet analysis both time and frequency information of the emission can be analysed and compared. Contralateral suppression of otoacoustic emissions was therefore measured in tinnitus patients (n = 26) and normal subjects (n = 37) and analysed using wavelets. No significant difference in suppression was found between the tinnitus patients and the control group.

Efeito de supressão nas vias auditivas: um estudo com os potenciais de média e longa latência

OBJETIVO: avaliar o efeito de supressão no Potencial Evocado Auditivo de Média e Longa Latência em indivíduos sem alterações auditivas, com presença de emissões otoacústicas (EOA) transientes em ambas as orelhas. MÉTODOS: foram avaliados 25 indivíduos (50 orelhas) de 18 a 30 anos de idade, de ambos os sexos, utilizando-se os Potenciais Evocados Auditivos de Média e Longa latência sem e com ruído branco contralateral. Os sujeitos não apresentavam queixa relacionada ao Processamento Auditivo. Foram verificados e comparados os valores numéricos das latências e amplitudes das ondas na avaliação convencional sem ruído e com ruído contralateral. RESULTADOS: a média aritmética da amplitude de resposta na situação com ruído (mascaramento) reduziu em todas as posições (C3/A1, C4/A1, C3/A2 e C4/A2), porém estes achados foram estatisticamente significantes nas posições C4/A1, C3/A2 e C4/A2. CONCLUSÃO: a diminuição da amplitude pode ter relação com o número de sinapses realizadas. O efeito de supressão na amplitude pode estar relacionado à ação do sistema eferente que suprime o número de sinapses neuronais.

Sistema auditivo eferente: efeito no processamento auditivo

O processamento da informação sonora depende da integridade das vias auditivas aferentes e eferentes. O sistema auditivo eferente pode ser avaliado por meio dos reflexos acústicos e da supressão das emissões otoacústicas. OBJETIVO: Verificar a atividade do sistema auditivo eferente, por meio da supressão das emissões otoacústicas (EOA) e da sensibilização do reflexo acústico no distúrbio de processamento auditivo. CASUÍSTICA E MÉTODO: Estudo prospectivo: 50 crianças com alteração de processamento auditivo (grupo estudo) e 38 sem esta alteração (grupo controle), avaliadas por meio das EOA na ausência e presença de ruído contralateral e da pesquisa dos limiares do reflexo acústico na ausência e presença de estímulo facilitador contralateral. RESULTADOS: O valor médio da supressão das EOA foi de até 1,50 dB para o grupo controle e de até 1,26 dB para o grupo estudo. O valor médio da sensibilização dos reflexos foi de até 14,60 dB para o grupo estudo e de até 15,21 dB para o grupo controle. Não houve diferença estatisticamente significante entre as respostas dos grupos controle e estudo em ambos os procedimentos. CONCLUSÃO: O grupo estudo apresentou valores reduzidos na supressão das EOA e valores aumentados na sensibilização do reflexo acústico, em relação ao grupo controle.

Efferent auditory system: its effect on auditory processing

Auditory processing depends on afferent and efferent auditory pathways integrity. The efferent auditory system may be assessed in humans by two non-invasive and objective methods: acoustic reflex and otoacoustic emissions suppression.

Aim

Analyze the efferent auditory system activity by otoacoustic emission suppression and acoustic reflex sensitization in human subjects with auditory processing disorders.

Method

Prospective study: fifty children with auditory processing disorders (study group) and thirty-eight children without auditory processing disorders (control group) were evaluated using otoacoustic emission with and without contralateral noise; and acoustic reflex with and without contralateral facilitating stimuli.

Results

OAE suppression mean value was equal to or less than 1.50 dB for the control group, and equal to or less than 1.26 dB for the study group. The mean sensitization reflex value was equal to or less than 14.60 dB for the study group and equal to or less than 15.21 dB for the control group. There was no statistically significant difference between the responses from the control group and the study group in both procedures.

Conclusion

The study group had lower OAE suppression values and higher acoustic reflex sensitization values when compared to the control group.

Subclinical Dysfunction of Cochlea and Cochlear Efferents in Migraine: An Otoacoustic Emission Study

Otoacoustic emission (OAE) testing enables us to identify the cochlear component of a hearing disorder and to monitor objectively minute changes in cochlear status undetectable by other audiological methods. Contralateral sound-induced suppression is mediated by medial superior olivary complex efferents which induce hyperpolarization counteracting the amplifying effects of outer hair cell (OHC) activity. The aim of this study was to assess functions of cochlea and its efferents in migraine using OAE testing and contralateral suppression of transiently evoked OAEs (TEOAE). Fifty-three migraineurs (106 ears) and 41 healthy subjects (82 ears) were included and pure tone audiometry (PTA), speech discrimination scores (SDS), distortion product OAE (DPOAE), TEOAE and contralateral suppression of TEOAEs were tested. PTA and SDS of migraineurs and controls were not different ( P > 0.05). DPOAEs were tested between 1 and 6 kHz and a significant difference was detected only at 5 kHz frequency, where DPOAE amplitudes in migraine with aura (MA) were lower than in controls ( P < 0.03). The mean amplitudes of TEOAEs were statistically insignificant between controls and migraine groups. Contralateral sound stimulus induced significant decrease in amplitudes of TEOAE ( P = 0.005) in controls. In patients with migraine without aura and MA, mean amplitudes of TEOAEs were not suppressed by contralateral sound stimulus ( P > 0.05). As PTA, SDS and DPOAE tests demonstrate normal functioning of inner ear between 1 and 4 kHz, absence of suppression of the TEOAEs by contralateral sound stimulation indicates the presence of dysfunction either in the medial olivocochlear complex in the brainstem or at the synaptic transmission between olivocochlear efferents and OHCs in the cochlea. Disruption in the contralateral suppression may be one of the mechanisms predisposing to the phonophobia symptom associated with migraine headache.

Absence of contralateral suppression of transiently evoked otoacoustic emissions in fibromyalgia syndrome

Objective:

To assess contralateral suppression of transiently evoked otoacoustic emissions in patients with fibromyalgia syndrome and normal hearing.

Methods:

Twenty-four female patients with fibromyalgia syndrome and 24 healthy female controls with normal hearing were assessed using pure tone audiometry and transiently evoked otoacoustic emissions.

Results:

All patients with fibromyalgia syndrome and all controls had normal hearing on pure tone audiometry. In the patients with fibromyalgia syndrome, the mean transiently evoked otoacoustic emission amplitude was 15.5 ± 4.8 dB. The mean transiently evoked otoacoustic emission amplitudes after contralateral suppression was 15.5 ± 4.9 dB. There was no statistically significant difference between the transiently evoked otoacoustic emission amplitudes measured before and after contralateral suppression (p > 0.05). In the controls, the mean transiently evoked otoacoustic emission amplitude was 12 ± 5 dB. The mean transiently evoked otoacoustic emission amplitudes after contralateral suppression was 11 ± 4.7 dB. There was a statistically significant decrease in transiently evoked otoacoustic emission amplitudes after contralateral suppression (p < 0.01).

Conclusion:

The mechanisms related to contralateral suppression of transiently evoked otoacoustic emissions seem dysfunctional in fibromyalgia syndrome. This dysfunction may be at the brain stem level, where the medial superior olivary complex is located, or at the synapses of medial superior olivary complex fibres with the outer hair cells in the cochlea. Demonstration of lack of contralateral suppression of transiently evoked otoacoustic emissions can be used as a diagnostic tool in patients with fibromyalgia syndrome.

Contralateral suppression of linear and nonlinear transient evoked otoacoustic emissions in neonates at risk for hearing loss

To investigate the transient evoked otoacoustic emissions (TEOAE) contralateral suppression in neonates at risk for hearing loss, 55 neonates at risk for hearing loss (risk group) and 72 full-term neonates not at such risk (control group) were bilaterally tested. In all neonates, the TEOAE were recorded in two stimulation modes (linear and nonlinear clicks), with and without contralateral acoustic stimulation. Findings revealed significant contralateral suppression of otoacoustic emissions in both groups, but the amount of TEOAE contralateral suppression was reduced for at risk group (p=0.001), supporting the hypothesis that medial olivocochlear bundle function is reduced in neonates at risk for hearing loss. The combination of contralateral acoustic stimulation and TEOAE enables easy and noninvasive study of auditory efferent function. However it should be emphasized that the reduction in TEOAE contralateral suppression in the risk group, statistically identified as a group effect, might not be detectable in individual cases. Further studies are needed in order to determine whether the lower amount of TEOAE contralateral suppression in neonates at risk for hearing loss represents a risk for developing auditory processing disorders.

LEARNING OUTCOMES

The reader will be introduced to the study using auditory efferent pathway activation by contralateral acoustic stimulation (CAS), resulting in the TEOAE suppression effect. The characteristics of TEOAE suppression in the neonatal population, in which it provides evidence of the reduced medial olivocochlear system function in those at risk for hearing loss, will also be addressed.

Measurement of the distribution of medial olivocochlear acoustic reflex strengths across normal-hearing individuals via otoacoustic emissions

A clinical test for the strength of the medial olivocochlear reflex (MOCR) might be valuable as a predictor of individuals at risk for acoustic trauma or for explaining why some people have trouble understanding speech in noise. A first step in developing a clinical test for MOCR strength is to determine the range and variation of MOCR strength in a research setting. A measure of MOCR strength near 1 kHz was made across a normal-hearing population (N = 25) by monitoring stimulus-frequency otoacoustic emissions (SFOAEs) while activating the MOCR with 60 dB SPL wideband contralateral noise. Statistically significant MOCR effects were measured in all 25 subjects; but not all SFOAE frequencies tested produced significant effects within the time allotted. To get a metric of MOCR strength, MOCR-induced changes in SFOAEs were normalized by the SFOAE amplitude obtained by two-tone suppression. We found this "normalized MOCR effect" varied across frequency and time within the same subject, sometimes with significant differences between measurements made as little as 40 Hz apart or as little as a few minutes apart. Averaging several single-frequency measures spanning 200 Hz in each subject reduced the frequency- and time-dependent variations enough to produce correlated measures indicative of the true MOCR strength near 1 kHz for each subject. The distribution of MOCR strengths, in terms of SFOAE suppression near 1 kHz, across our normal-hearing subject pool was reasonably approximated by a normal distribution with mean suppression of approximately 35% and standard deviation of approximately 12%. The range of MOCR strengths spanned a factor of 4, suggesting that whatever function the MOCR plays in hearing (e.g., enhancing signal detection in noise, reducing acoustic trauma), different people will have corresponding differences in their abilities to perform that function.

Auditory Efferent Function Is Affected in Multiple Sclerosis

OBJECTIVE

This study evaluated efferent medial olivocochlear (MOC) function in patients with multiple sclerosis (MS). Various afferent auditory abnormalities have been described in MS, but there is a paucity of data on efferent function. The brain stem is a site of predilection for MS plaques and the efferent MOC pathway may be affected at this level.

METHODS

The study included 30 patients who had normal hearing. According to MRI findings, they were divided into two groups: those with an identifiable brain stem lesion (n = 10) and those with MS lesions in other parts of the central nervous system but without demonstrable MS plaques in the brain stem (n = 20). MOC function was evaluated by the olivocochlear suppression test, using transient evoked otoacoustic emissions. All subjects underwent standard auditory tests, including pure-tone audiometry and recording of auditory brain stem evoked responses. Twenty-two healthy subjects with normal hearing, matched for age and gender, served as a reference group for the auditory data.

RESULTS

The results showed that 66.6% of all patients had reduced MOC function, particularly those (90%) with identified lesions of the brain stem on MRI. Furthermore, abnormal MOC function was found in 55% patients without evidence of a brain stem lesion on MRI.

CONCLUSIONS

This study provides the evidence for a deficit of efferent auditory function in the majority of patients with MS. Taking into consideration the possible roles of the MOC system in processing of auditory information, abnormal MOC suppression in patients with MS may explain a variety of auditory presentations that are currently largely overlooked. This study also highlights the diagnostic value of the MOC suppression test as a site-of-lesion diagnostic test in MS and in identifying subtle brain stem lesions undetected by MRI, suggesting that subtle brain stem lesions may exist and that the MOC suppression test is sufficiently sensitive to detect them. Accordingly, the MOC suppression test may provide a tool for an early diagnosis of MS.

Effect of age on speech recognition in noise and on contralateral transient evoked otoacoustic emission suppression

Introduction:

We aimed to study the influence of age, in normal hearing individuals, on: the masking level difference test, the speech recognition in noise test, the transient evoked otoacoustic emissions test, and the contralateral transient evoked otoacoustic emission suppression test. We also aimed to research the effect of age when using these tests to evaluate the central auditory nervous system.

Methods:

Transient evoked otoacoustic emissions and contralateral transient evoked otoacoustic emission suppression were measured in all subjects. Subjects also underwent masking level difference and speech recognition in noise tests.

Results:

We found a decrease in transient evoked otoacoustic emission amplitudes, speech recognition in noise scores and hearing thresholds with age. We also found that higher masking level difference values were associated with lower speech recognition in noise scores and contralateral transient evoked otoacoustic emission suppression values.

Conclusion:

We conclude that decreasing speech recognition in noise scores are associated with decreasing contralateral transient evoked otoacoustic emission supression values. This effect may be related to medial efferent system dysfunction.

Bias due to noise in otoacoustic emission measurements

Measurements of otoacoustic emission (OAE) magnitude are often made at low signal/noise ratios (SNRs) where measurement noise generates bias and variability errors that have led to the misinterpretation of OAE data. To gain an understanding for these errors and their effects, a two part investigation was carried out. First, the nature of OAE measurement noise was investigated using human data from 50 stimulus-frequency OAE experiments involving medial olivocochlear reflex (MOCR) activation. The noise was found to be reasonably approximated by circular Gaussian noise. Furthermore, when bias errors were taken into account, measurement variability was not found to be affected by MOCR activation as had been previously reported. Second, to quantify the errors circular Gaussian noise produces for different methods of OAE magnitude estimation for distortion-product, stimulus-frequency, and spontaneous OAEs, simulated OAE measurements were analyzed via four different magnitude estimation methods and compared. At low SNRs (below -6 dB), estimators involving Rice probability density functions produced less biased estimates of OAE magnitudes than conventional estimation methods, and less total rms error-particularly for spontaneous OAEs. They also enabled the calculation of probability density functions for OAE magnitudes from experimental data.

Contralateral suppression of otoacoustic emission in patients with tinnitus

Introduction: The medial olivocochlear bundle effect is studied through the suppression of otoacoustic emissions and seems to be influenced by the laterality of the central nervous system, presenting no symmetry between right and left ear. A dysfunction of this bundle may be involved in the generation of tinnitus, although this fact was not confirmed. Objectives: Study the suppression of distortion product otoacoustic emissions in tinnitus patients. Material and Method: A case-controlled study involving 44 tinnitus patients from the Tinnitus Group of the ENT Department of the University of São Paulo Medical School and 44 controls who underwent distortion product otoacoustic emissions testing with and without contralateral noise. Only the results from the right ears from both groups were compared. Results: There was a relationship between the presence of tinnitus and the absence of suppression at all frequencies studied (OR>2.1). Conclusion: There was a correlation between diminished effectiveness of the medial olivocochlear bundle and the presence of tinnitus.

Mudanças das emissões otoacústicas por transientes na supressão contralateral em lactentes

TEMA: tem sido sugerido que a função do sistema olivo coclear medial (SOCM) pode ser avaliada pelo efeito de supressão das emissões otoacústicas por transientes (EOAT). O ruído competitivo tem um efeito inibitório no funcionamento das células ciliadas externas reduzindo o nível das emissões otoacústicas. Apesar de não haver crescimento pós natal da cóclea, o crescimento da orelha média e o desenvolvimento do processamento auditivo continuam após o nascimento. OBJETIVO: analisar as mudanças no SOCM relacionadas à idade por meio da supressão das EOAT em lactentes saudáveis. MÉTODO: 25 lactentes a termo sem indicadores de risco auditivo foram avaliados em dois momentos: ao nascimento e no sexto mês de vida. Nas duas idades as EOAT foram captadas no modo "Quickscreen", estímulo clique não linear a 78dB peNPS, nas duas orelhas, com e sem ruído contralateral apresentado a 60dB NPS. RESULTADOS: a análise dos dados por meio da ANOVA revelou significante supressão contralateral das EOAT em ambos grupos, porém tanto os níveis das EOAT quanto a magnitude da supressão contralateral das EOAT foram menores no sexto mês de vida quando comparados com a fase neonatal (p<0,01). O efeito de supressão das EOAT no período neonatal foi 2,81dB (± 0,19dB) e no sexto mês de vida foi 1,41dB (± 0,29dB). CONCLUSÃO: a magnitude da supressão das EOAT diminuiu do nascimento ao sexto mês de idade. A associação entre a estimulação acústica contralateral e um sistema, disponível comercialmente, rápido na medida das EOAT possibilita o monitoramento não invasivo dos mecanismos eferentes auditivos e parece ser clinicamente promissor na avaliação do estado coclear e do desenvolvimento da função eferente auditiva de lactentes de risco.

Pathophysiological Changes of the Central Auditory Pathway after Blunt Trauma of the Head

It is the aim of the present paper to correlate clinical symptoms of auditory dysfunction (tinnitus, hyperacusis, hearing loss) one year on average after a blunt trauma of the head with objective audiological test results (otoacoustic emission and auditory brainstem response testing, impedance audiometry) and to compare these findings to controls without history of head trauma. Thirty-one patients (24-56 years) were included. They were largely female (n = 26). The clinical and otolaryngological examination (including otoscopy) of all patients revealed no pathological abnormalities. Pure-tone audiograms were normal with one exception (pre-existing noise-induced hearing loss) as well as tympanograms. The main auditory symptoms were tinnitus (n = 9), hyperacusis (n = 2) and a reported transient hearing loss immediately after the trauma (n = 16) (which had improved at the time of examination). The results of testing the central auditory pathway showed that the transiently evoked otoacoustic emissions (otoemissions) revealed statistically significant differences between amplitude differences of all patients as well as patients with tinnitus and controls in the linear, but not in the non-linear stimulation mode. A complete loss of stapedial reflex responses was found in 12 of the patients and a partial (irregular) loss (in at least more than two frequencies) in four additional patients. Auditory brainstem responses (ABR) were normal in all patients, but 76% had lowered loudness discomfort levels (LDL). Blunt trauma of the head can lead to auditory dyfunction, probably as a result of diffuse axonal injury of the central auditory pathway. An initial sensorineural hearing loss after the trauma (as a result of the inner ear fluid concussion) was transiently reported only. Auditory symptoms play a minor role in the so-called "postconcussive syndrome," but should be considered and evaluated fully.