A Clinical Study of the Efferent Auditory System in Patients With Normal Hearing Who Have Acute Tinnitus

Evidence of cochlear neural degeneration in normal-hearing subjects with tinnitus

Tinnitus, reduced sound-level tolerance, and difficulties hearing in noisy environments are the most common complaints associated with sensorineural hearing loss in adult populations. This study aims to clarify if cochlear neural degeneration estimated in a large pool of participants with normal audiograms is associated with self-report of tinnitus using a test battery probing the different stages of the auditory processing from hair cell responses to the auditory reflexes of the brainstem. Self-report of chronic tinnitus was significantly associated with (1) reduced cochlear nerve responses, (2) weaker middle-ear muscle reflexes, (3) stronger medial olivocochlear efferent reflexes and (4) hyperactivity in the central auditory pathways. These results support the model of tinnitus generation whereby decreased neural activity from a damaged cochlea can elicit hyperactivity from decreased inhibition in the central nervous system.

Effect of Tinnitus on Sleep Quality and Insomnia

Introduction  Tinnitus is a conscious perception of a sound resulting from abnormal activity within the nervous system. A relevant percentage of tinnitus patients report symptoms severe enough to significantly affect quality of life, including sleep disorders. Objective  To analyze the sleep quality, insomnia, daytime sleepiness, and risk of obstructive sleep apnea (OSA) in participants with tinnitus. Methods  The sample comprised 18 adults and older adults aged between 18 and 85 years old (mean age = 58.7 ± 17.5 years old), females and males, with complaint of continuous tinnitus for > 1 month. The instruments used were the Tinnitus Handicap Inventory (THI) questionnaire, the Insomnia Severity Index, the Pittsburgh Sleep Quality Index, the Epworth Sleepiness Scale, and the STOP-Bang questionnaire. Results  By means of the THI questionnaire, the tinnitus severity degree reported by most participants was mild (27.8%) and moderate (27.8%), having a positive (r = 0.582) and significant (0.011) correlation to sleep quality, measured by means of the Pittsburgh questionnaire. There was a positive correlation between the Insomnia Severity Index and tinnitus handicap (r = 0.499; p  = 0.035). A total of 72.2% of the participants self-assessed their sleep quality as poor, in addition to moderate insomnia (27.8%), although there is low risk of OSA (66.7%), without complaints of excessive daytime sleepiness (72.2%). Conclusion  Subjects with tinnitus complaint self-rated their sleep quality as poor. Moreover, the higher the reported tinnitus handicap, the greater the symptoms of insomnia. There was no influence of tinnitus in relation to daytime sleepiness and no relationship between the severity of tinnitus and the risk of OSA.

Tinnitus: impact on patients in relation to audiological findings

Objective

Tinnitus is a common auditory disorder in which patients experience noise in the absence of an external source. It is a consequence of irreversible cochlear damage. This study examined the distortion product otoacoustic emissions and P300 components of event-related potentials.

Method

This study included a control group of 25 normal-hearing adults not complaining of tinnitus and a study group that consisted of 45 normal-hearing adults complaining of tinnitus. Measures included patient history, basic audiological evaluation, the Arabic version of Tinnitus Handicap Inventory, distortion product otoacoustic emissions testing and P300 recording.

Results

The study group showed significantly higher hearing thresholds at all frequencies as well as delayed latencies and reduced amplitude of P300. The Tinnitus Handicap Inventory showed mean scores of 35.2 ± 16.9, and the distortion product gram showed higher amplitudes in the control group.

Conclusion

Patients with tinnitus might have neural dysfunction at either peripheral or central levels of the auditory pathway.

Evaluating the Function of the Medial Olivocochlear Bundle in Patients With Bilateral Tinnitus

Purpose No study has investigated the effects of contralateral noise (CN) on speech-in-noise perception (SINP) in listeners with tinnitus. The mechanisms underlying the involvement of medial olivocochlear (MOC) reflex with SINP remain to be elucidated. This study aimed to investigate the MOC function in patients with bilateral tinnitus by measuring distortion product otoacoustic emission and SINP. Method Eighteen patients with bilateral tinnitus (one male and 17 females; age: M ± SD = 45.61 ± 10.18 years) and 19 listeners without tinnitus (six males and 13 females; age: M ± SD = 34.11 ± 8.35 years) were recruited for the study. Each subject underwent distortion product otoacoustic emission measurement and the SINP test for both ears. The effects of CN on these two measurements were compared between tinnitus ears (TEs) and no-tinnitus ears (NTEs). Results The presence of CN significantly reduced distortion product (DP) amplitudes and improved SINP for TEs, and the amounts of DP suppression and SINP improvement were similar to those in NTEs. Improvement of SINP was positively correlated with DP suppression at 6185 Hz for NTEs and at 1640 Hz for TEs. Conclusions The results of this study suggest that the amounts of DP suppression and SINP improvement were similar between listeners with and without tinnitus. For both ear groups, the MOC reflex was involved with SINP at specific frequencies. Any clinical test outcomes with regard to the MOC bundle in patients with tinnitus should be interpreted with caution until further studies are conducted.

Towards a Mechanistic-Driven Precision Medicine Approach for Tinnitus

In this position review, we propose to establish a path for replacing the empirical classification of tinnitus with a taxonomy from precision medicine. The goal of a classification system is to understand the inherent heterogeneity of individuals experiencing and suffering from tinnitus and to identify what differentiates potential subgroups. Identification of different patient subgroups with distinct audiological, psychophysical, and neurophysiological characteristics will facilitate the management of patients with tinnitus as well as the design and execution of drug development and clinical trials, which, for the most part, have not yielded conclusive results. An alternative outcome of a precision medicine approach in tinnitus would be that additional mechanistic phenotyping might not lead to the identification of distinct drivers in each individual, but instead, it might reveal that each individual may display a quantitative blend of causal factors. Therefore, a precision medicine approach towards identifying these causal factors might not lead to subtyping these patients but may instead highlight causal pathways that can be manipulated for therapeutic gain. These two outcomes are not mutually exclusive, and no matter what the final outcome is, a mechanistic-driven precision medicine approach is a win-win approach for advancing tinnitus research and treatment. Although there are several controversies and inconsistencies in the tinnitus field, which will not be discussed here, we will give a few examples, as to how the field can move forward by exploring the major neurophysiological tinnitus models, mostly by taking advantage of the common features supported by all of the models. Our position stems from the central concept that, as a field, we can and must do more to bring studies of mechanisms into the realm of neuroscience.

Polysomnographic Findings in Patients With Chronic Tinnitus

Objectives:

Tinnitus is an auditory sensation in the absence of any external stimulus. It has a negative impact on quality of life and interferes with concentration, sleep, social activities, and even emotional stability. The aim of this study was to compare sleep architecture in patients with and without chronic subjective tinnitus.

Methods:

This was an observational, noninterventional, and prospective study. The sample consisted of 50 individuals of both sexes aged 20 to 60 years. Twenty-five patients with tinnitus constituted the study group, and for comparison, a control group consisting of 25 patients without reported tinnitus was formed. The patients underwent polysomnography and were administered the Epworth Sleepiness Scale, Tinnitus Handicap Inventory, and visual analog scales.

Results:

The group with tinnitus had higher mean values in sleep stages 1 and 2, and lower mean values in stage 3 and in rapid eye movement (REM) sleep, compared with the control group, and this difference was significant only for REM sleep ( P = .031). This demonstrates that patients with tinnitus remained longer in shallow sleep and spent less time in deep sleep (stage 3) and REM sleep.

Conclusions:

This study shows that patients with tinnitus have significant alterations in REM sleep latency as well as the REM sleep phase.

The Association Between Cochlear and Retrocochlear Disorders with Tinnitus with Normal Hearing Thresholds

Tinnitus is the perception of hearing the sound without any sound stimulus. It is a symptom of abnormality in a form of conductive disorder when it comes from the outer ear canal and middle ear. A tinnitus complaint has a normal hearing threshold but it has been not fully recognized its causes. Thus, an objective evaluation is needed to locate the abnormality by using OAE and BERA test. To analyze the association of TEOAE, DPOAE, and BERA to locate cochlear and retrocochlear disorders in tinnitus patients with normal hearing threshold. The study was conducted from August to November 2010 until the number of samples was fulfilled in Outpatient Clinic and Audiology Unit in Department of Otolaryngology-Head and Neck Surgery, Dr. Soetomo General Hospital Surabaya. The inclusion criteria in this study included: patients aged 20-50 years old, hearing threshold of ≤ 25 dB, type A tympanogram. The comparison and the association test of TEOAE, DPOAE and BERA in tinnitus group were: TEOAE-BERA analysis result using Mc Nemar obtained p = 0.006, Kappa p = 0.047, likelihood ratio p = 0.066, and the result of DPOAE-BERA analysis using Mc Nemar obtained p = 0.008, Kappa p = 0.439, likelihood ratio p = 0.336. There was a difference in the results of DPOAE examination between tinnitus patients with normal hearing threshold and the control group. There was no difference in TEOAE and BERA test results between tinnitus patients with normal hearing threshold and the control group. This indicates an abnormality in the cochlear.

Objective assessment of subjective tinnitus through contralateral suppression of otoacoustic emissions by white noise: effects of frequency, gender, tinnitus bilaterality and age

SUMMARY

Accumulating evidence seems to support an association between tinnitus and medial olivocochlear bundle (MOCB) dysfunction. Most studies use patient/control comparisons to support this correlation. The aim of this study was to investigate the hypothesis in a substantially different way and evaluate the roles of gender, age, frequency and tinnitus bilaterality as possible confounding factors. The population consisted of 78 normal hearing patients with chronic tinnitus, 28 normal hearing controls, 19 presbycousic tinnitus patients and 13 presbycousic controls (n = 276 ears). Mean suppression amplitudes of transient evoked otoacoustic emissions (TEOAEs) and distortion product OAEs (DPOAEs) by contralateral white noise (50 dB SPL) were computed. Mean suppression values < 1 dB SPL or < 2 dB SPL were validated as positive test results. Overall suppression (OS) values < 1 dB SPL were qualified as a diagnostic test of moderate positive predictive value for both DPOAEs and TEOAEs, while OS values < 2 dB SPL were found to be of large negative predictive value for DPOAEs and moderate for TEOAEs. Mean suppression values (for all frequencies, OS) are of higher diagnostic value than suppression values corresponding to either lower (1-2 kHz) or higher frequencies (2.8-4 kHz for TEOAEs and 2.8-6 kHz for DPOAEs). After excluding patients with unilateral tinnitus from the analysis, correlations were found to be stronger. Useful correlations were also attributed for all age groups < 61 years. In females, OAE suppression seems to have a stronger positive predictive value, while in males it seems to have a stronger negative predictive value. OAE-based assays of MOCB function as an objective diagnostic tool for subjective tinnitus might deserve further investigation. Tinnitus uni- or bi-laterality is a confounding factor, which probably confirms the observation that defective function of the MOCB usually applies to the contralateral ear as well. Gender is an additional confounding factor, while correlations can be verified for all age groups < 61 years old.

Transition from Acute to Chronic Tinnitus: Predictors for the Development of Chronic Distressing Tinnitus

Background

Acute tinnitus and its transition to chronic tinnitus are poorly investigated, and factors associated with amelioration versus exacerbation are largely unknown. Aims of this study were to identify early predictors for the future development of tinnitus severity.

Method

Patients with tinnitus of no longer than 4 weeks presenting at an otolaryngologist filled out questionnaires at inclusion (T1), as well as 3 (T3), and 6 months (T4) after tinnitus onset. 6 weeks after onset, an interview was conducted over the phone (T2). An audiogram was taken at T1, perceived tinnitus loudness, and tinnitus-related distress were assessed separately and repeatedly together with oversensitivity to external sounds and the levels of depression and anxiety. Furthermore, coping strategies with illness were recorded.

Results

Complete remission until T4 was observed in 11% of the 47 participants, while voiced complaints at onset were stable in the majority. In the subgroup with a relevant level of depression at T1, tinnitus-related distress worsened in 30% until T4. For unilateral tinnitus, perceived loudness in the chronic condition correlated strongly with hearing loss at 2 kHz on the tinnitus ear, while a similar correlation was not found for tinnitus located to both ears or within the head.

Conclusion

Results suggest early manifestation of tinnitus complaints, and stress the importance of screening all patients presenting with acute tinnitus for levels of depression and tinnitus-related distress. Furthermore, hearing levels should be monitored, and use of hearing aids should be considered to reduce tinnitus loudness after having ascertained that sound sensitivity is within normal range.

Polysomnography Applied to Patients with Tinnitus: A Review

Introduction  Tinnitus has been defined as an “auditory phantom perception,” meaning that tinnitus results from an abnormal activity within the nervous system, in the absence of any internal or external acoustic stimulation. About 10 to 15% of the adult population is affected by tinnitus, and a relevant percentage of tinnitus sufferers experience symptoms severe enough to significantly affect quality of life, including sleep disturbances, work impairment, and, in some cases, psychiatric distress. The self-rated complaints about tinnitus focus on emotional distress, auditory perceptual difficulties, and sleep disturbances.

Objectives  To evaluate the works that show sleep disorders in patients with tinnitus, and sleep disorders assessed by polysomnography.

Data Synthesis  We found four studies with polysomnography to assess sleep disorders in patients with tinnitus. The first study evaluated 80 patients who were military personnel without major psychiatric disturbances, and their tinnitus was associated with noise-induced permanent hearing. The second study was a prospective, case-control, nonrandomized study of 18 patients affected by chronic tinnitus who were compared with a homogeneous control group consisting of 15 healthy subjects. The last work evaluated questionnaires mailed to patients before their initial appointment at the Oregon Health Sciences University Tinnitus Clinic between 1994 and 1997. These questionnaires requested information pertaining to insomnia, tinnitus severity, and loudness. Follow-up questionnaires were mailed to 350 patients 1 to 4 years (mean 5 ± 2.3 years) after their initial appointment at the clinic.

Conclusion  There are few studies with polysomnography for the evaluation of patients with sleep disorders caused by tinnitus. This shows the need for more studies on this subject.

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.

Evidence and evidence gaps in tinnitus therapy

A nearly endless number of procedures has been tried and in particular sold for the treatment of tinnitus, unfortunately they have not been evaluated appropriately in an evidence-based way. A causal therapy, omitting the tinnitus still does not exist, actually it cannot exist because of the various mechanisms of its origin. However or perhaps because of that, medical interventions appear and reappear like fashion trends that can never be proven by stable and reliable treatment success. This contribution will discuss and acknowledge all current therapeutic procedures and the existing or non-existing evidence will be assessed. Beside external evidence, the term of evidence also encompasses the internal evidence, i.e. the experience of the treating physician and the patient's needs shall be included. While there is no evidence for nearly all direct procedures that intend modulating or stimulating either the cochlea or specific cervical regions such as the auditory cortex, there are therapeutic procedures that are acknowledged in clinical practice and have achieved at least a certain degree of evidence and generate measurable effect sizes. Those are in particular habituation therapy and psychotherapeutic measures, especially if they are combined with concrete measures for improved audio perception (hearing aids, CI, hearing therapies).

Prognostic factors for the outcomes of intratympanic dexamethasone in the treatment of acute subjective tinnitus

OBJECTIVE

To determine the prognostic factors for the outcomes of treating acute subjective tinnitus with intratympanic dexamethasone (ITD).

STUDY DESIGN

Retrospective chart review.

SETTING

Tertiary referral center.

PATIENTS

We enrolled 139 subjects who were treated with ITD for acute subjective tinnitus with symptoms lasting for 3 months or less. Overall, 114 of 139 subjects completed questionnaires 3 months after treatment or fully recovered within 3 months. Audiograms were performed 3 months after treatment in 43 patients.

INTERVENTION

ITD for acute subjective tinnitus.

MAIN OUTCOME MEASURE

Quantitative assessment of the severity of tinnitus by questionnaires and changes in hearing thresholds at all frequencies by pure-tone audiometry.

RESULTS

Tinnitus was cured in 43 of 114 patients (37.7%) within 3 months. The mean tinnitus loudness score, the mean tinnitus awareness score, and the mean tinnitus handicap inventory score were significantly reduced at 3 months after ITD. Audiometric responses were detected in 12 of 43 patients (27.9%) who underwent follow-up audiograms. The cure rate was significantly greater in patients with symptoms lasting for 2 weeks or less than in patients with symptoms lasting for more than 1 month (64.7% vs. 15.7%; p < 0.05). The mean global improvement index for tinnitus was significantly greater in patients with unilateral tinnitus than in patients with bilateral tinnitus (6.2 ± 1.9 vs. 5.0 ± 2.0; p < 0.05). Among patients with unilateral tinnitus, the audiometric response rate was significantly greater in patients with asymmetric hearing threshold than in patients with symmetric hearing threshold (48.8% vs. 4.8%; p < 0.01). The cure rate was significantly associated with the duration of symptoms. Unilateral tinnitus and audiologic asymmetry were positively associated with the audiometric response rate.

CONCLUSIONS

The duration of symptoms affected the cure rate of ITD for acute subjective tinnitus. Unilateral tinnitus was associated with better improvements in symptoms than bilateral tinnitus. Furthermore, unilateral tinnitus and audiologic asymmetry were positively associated with the audiometric response.

Tinnitus and normal hearing: a study on contralateral acoustic reflex

PURPOSE

The aim of this study was to evaluate the difference of the contralateral acoustic reflex (AR) threshold between adult subjects with hearing within clinically normal limits, with and without tinnitus.

METHOD

The study sample in this exploratory, descriptive, and comparative study comprised 40 female subjects who were evaluated: 20 had tinnitus and 20 formed the control group. The contralateral AR threshold was evaluated at the frequencies of 500, 1000, and 2000 Hz.

RESULTS

Elevated or absent AR thresholds were found only in subjects with complaints of tinnitus. At all frequencies and in either ear, the median AR threshold was higher in the group that complained of tinnitus (100.0 dB; range = 95.0–100.0 dB) compared with the control group (90.0 dB; range = 86.3–95.0 dB; p < .01). There was a statistically significant difference ( p < .05) in the group with tinnitus, in each of the frequencies studied and in both the right and left ear.

CONCLUSION

The results suggest that evaluation of the efferent system, through AR, could be an important tool for the differential diagnosis of tinnitus in patients whose hearing was within clinically normal limits.

Increased contralateral suppression of otoacoustic emissions indicates a hyperresponsive medial olivocochlear system in humans with tinnitus and hyperacusis

Atypical medial olivocochlear (MOC) feedback from brain stem to cochlea has been proposed to play a role in tinnitus, but even well-constructed tests of this idea have yielded inconsistent results. In the present study, it was hypothesized that low sound tolerance (mild to moderate hyperacusis), which can accompany tinnitus or occur on its own, might contribute to the inconsistency. Sound-level tolerance (SLT) was assessed in subjects (all men) with clinically normal or near-normal thresholds to form threshold-, age-, and sex-matched groups: 1) no tinnitus/high SLT, 2) no tinnitus/low SLT, 3) tinnitus/high SLT, and 4) tinnitus/low SLT. MOC function was measured from the ear canal as the change in magnitude of distortion-product otoacoustic emissions (DPOAE) elicited by broadband noise presented to the contralateral ear. The noise reduced DPOAE magnitude in all groups ("contralateral suppression"), but significantly more reduction occurred in groups with tinnitus and/or low SLT, indicating hyperresponsiveness of the MOC system compared with the group with no tinnitus/high SLT. The results suggest hyperresponsiveness of the interneurons of the MOC system residing in the cochlear nucleus and/or MOC neurons themselves. The present data, combined with previous human and animal data, indicate that neural pathways involving every major division of the cochlear nucleus manifest hyperactivity and/or hyperresponsiveness in tinnitus and/or low SLT. The overactivation may develop in each pathway separately. However, a more parsimonious hypothesis is that top-down neuromodulation is the driving force behind ubiquitous overactivation of the auditory brain stem and may correspond to attentional spotlighting on the auditory domain in tinnitus and hyperacusis.

[High-resolution distortion-product otoacoustic emissions: method and clinical applications]

Unlike pure tone thresholds that assess both peripheral and central sound processing, distortion-product otoacoustic emissions (DPOAEs) selectively mirror the functioning of the cochlear amplifier. High resolution DPOAEs are missing in the toolbox of routine audiometry due to the fact that high resolution DPOAE measurements are more time-consuming when compared to normal clinical DP grams with rough frequency resolution. Measurements of high resolution DPOAEs allow an early assessment of beginning sensory cell damage due to sound overexposure or administration of ototoxic drugs. When using a rough grid, sensory cell damage would be overlooked as in the early state damage only appears at some distinct cochlear sites. A review is given on the method and application of high resolution DPOAEs.

Tinnitus pitch and minimum masking levels in different etiologies

OBJECTIVE

We sought to determine whether the results of audiological tests and tinnitus characteristics, particularly tinnitus pitch and minimum masking level (MML), depend on tinnitus etiology, and what other etiology-specific tinnitus characteristics there are.

DESIGN

The patients answered questions concerning tinnitus laterality, duration, character, aggravation, alleviation, previous treatment, and circumstances of onset. The results of tympanometry, pure-tone audiometry, distortion-product otoacoustic emissions, tinnitus likeness spectrum, MML, and uncomfortable loudness level were evaluated.

STUDY SAMPLE

Patients with several tinnitus etiological factors were excluded. The remaining participants were divided into groups according to medical history: acute acoustic trauma: 67 ears; chronic acoustic trauma: 82; prolonged use of oral estrogen and progesterone contraceptives: 46; Ménière's disease: 25; congenital hearing loss: 19; sensorineural sudden deafness: 40; dull head trauma: 19; viral labyrinthitis: 53; stroke: 6; presbycusis: 152. Data of 509 ears were analysed.

RESULTS

Tinnitus pitch was highest in patients with acute acoustic trauma and lowest in patients receiving estrogen and progesterone. MML was lowest after acute acoustic trauma and in congenital hearing loss, and highest after a stroke and in the case of presbytinnitus.

CONCLUSIONS

Tinnitus pitch and MML are etiology dependent.

Auditory cortex basal activity modulates cochlear responses in chinchillas

BACKGROUND

The auditory efferent system has unique neuroanatomical pathways that connect the cerebral cortex with sensory receptor cells. Pyramidal neurons located in layers V and VI of the primary auditory cortex constitute descending projections to the thalamus, inferior colliculus, and even directly to the superior olivary complex and to the cochlear nucleus. Efferent pathways are connected to the cochlear receptor by the olivocochlear system, which innervates outer hair cells and auditory nerve fibers. The functional role of the cortico-olivocochlear efferent system remains debated. We hypothesized that auditory cortex basal activity modulates cochlear and auditory-nerve afferent responses through the efferent system.

METHODOLOGY/PRINCIPAL FINDINGS

Cochlear microphonics (CM), auditory-nerve compound action potentials (CAP) and auditory cortex evoked potentials (ACEP) were recorded in twenty anesthetized chinchillas, before, during and after auditory cortex deactivation by two methods: lidocaine microinjections or cortical cooling with cryoloops. Auditory cortex deactivation induced a transient reduction in ACEP amplitudes in fifteen animals (deactivation experiments) and a permanent reduction in five chinchillas (lesion experiments). We found significant changes in the amplitude of CM in both types of experiments, being the most common effect a CM decrease found in fifteen animals. Concomitantly to CM amplitude changes, we found CAP increases in seven chinchillas and CAP reductions in thirteen animals. Although ACEP amplitudes were completely recovered after ninety minutes in deactivation experiments, only partial recovery was observed in the magnitudes of cochlear responses.

CONCLUSIONS/SIGNIFICANCE

These results show that blocking ongoing auditory cortex activity modulates CM and CAP responses, demonstrating that cortico-olivocochlear circuits regulate auditory nerve and cochlear responses through a basal efferent tone. The diversity of the obtained effects suggests that there are at least two functional pathways from the auditory cortex to the cochlea.

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.

Occurrence and suppression effect of otoacoustic emissions in normal hearing adults with tinnitus and hyperacusis

The association between tinnitus and hyperacusis is common according to the literature.

AIM

To verify the occurrence and the suppression effect of transient otoacoustic emissions (TEOAE), the existence of association between tinnitus degrees and hyperacusis degrees, and between the suppressive effect of TEOAE and laterality, tinnitus and hyperacusis degrees in normal hearing adults with complaints of tinnitus and hyperacusis.

MATERIALS AND METHODS

25 normal hearing subjects with complaints of hyperacusis and tinnitus were studied in this cross-sectional study. The Tinnitus Handicap Inventory (THI) was used for the classification of tinnitus degrees, and the Loudness Discomfort Level (LDL) for the hyperacusis classification.

RESULTS

The occurrence of TEOAE ranged from 33 to 88%. We observed the presence of TEOAE suppression effect on 63.7% in the right ear and 81.7% in the left ear. There was no significant correlation between the degrees of tinnitus and hyperacusis in both ears. No statistically significant associations between the TEOAE suppression effect and laterality, tinnitus degrees and hyperacusis degrees were found.

CONCLUSION

The occurrence of TEOAE was lower than that found in normal hearing adults. A higher percentage of the presence of TEOAE suppression effect has been found in both ears. No association between the variables was observed.

Measurement of medial olivocochlear efferent activity in humans: comparison of different distortion product otoacoustic emission-based paradigms

OBJECTIVE

To assess the suitability of contralateral suppression (CS) of distortion product otoacoustic emissions (DPOAEs) for measurement of activity of the medial olivocochlear (MOC) efferents.

BACKGROUND

The MOC efferent system has been shown to be involved in sound discrimination, selective attention to tones, sound localization, and protection of the cochlea against noise. A great variety of paradigms for measurement of MOC activity by CS of OAE (MOC reflex [MOCR]), has been described. An issue of this approach is the dependence of the CS values on stimulus parameters, especially when DPOAE are used.

METHODS

Four different measurement paradigms, which used different combinations of stimulus frequencies and primary tone levels, were applied in 16 human subjects.

RESULTS

Mean absolute values of CS were in the range of 1.2 to 2.6 dB. The use of different stimulus parameters produced not only MOCR values of different size-which was expected-but, in many cases, also different relative classifications of the subjects according to their MOCR strength.

CONCLUSION

The suppression effects on DPOAE demonstrated in this study reflect MOC activity. However, the new conclusion from our data is that CS of DPOAE measurements, as they were used in this study, may not allow for a consistent quantitative classification of human subjects according to their MOCR strength. This finding concerns interpretation of previous studies using CS of DPOAE and analogous future studies. One future approach may lie in the separation of the DPOAE components to distinguish interference phenomena, which complicate interpretation of CS values.

Prevalence and significance of high-frequency hearing loss in subjectively normal-hearing patients with tinnitus

OBJECTIVES

We investigated the incidences of high-frequency hearing loss (HFHL; above 2 kHz) and extended high-frequency hearing loss (EHFHL; above 8 kHz) in patients with tinnitus and subjectively normal hearing, and evaluated their effects on the clinical and audiological features of the patients.

METHODS

The sample included 85 patients with sensorineural tinnitus who had normal hearing sensitivity in the frequencies from 250 Hz to 2 kHz, and who had undergone extended high-frequency audiometry between July 2009 and February 2010. We investigated the incidences of HFHL and EHFHL in these patients and analyzed the significance of the hearing losses.

RESULTS

The incidence of HFHL or EHFHL was 88%. The proportion of patients with EHFHL, among the patients who had normal hearing sensitivity up to 8 kHz, was about 74%. The patients with normal hearing sensitivity at all test frequencies were significantly younger, had larger otoacoustic emissions, and had tinnitus that was less loud as measured by tinnitus matching than did the subjects with HFHL and/or EHFHL. However, other comparisons of clinical factors in the three groups did not show any differences.

CONCLUSIONS

Even if patients with tinnitus do not have any subjective hearing impairment, most of them have HFHL and/or EHFHL. The effects on the clinical features of the patients are still vague.

Contralateral suppression of otoacoustic emissions in tinnitus patients

OBJECTIVE

To compare the functioning of the medial olivocochlear efferent system between tinnitus patients and control subjects.

STUDY DESIGN

Prospective, nonrandomized controlled analysis of suppression of otoacoustic emissions with contralateral acoustic stimulation.

SETTING

Tertiary referral center.

PATIENTS

Initial analysis of 97 tinnitus patients and 44 control subjects with click-evoked otoacoustic emission measurement. If subjects had reproducible otoacoustic emissions at 80 dB SPL, suppression of otoacoustic emission with contralateral acoustic stimulation was measured with a 65-dB click stimulus. This resulted in inclusion of 44 ears of tinnitus patients and 57 ears of control subjects.

INTERVENTION

Suppression of the otoacoustic emissions generated by the 65-dB click stimulus was tested using contralateral broadband noise at 70 dB SPL. Suppression was calculated in half-octave frequency bands centered at 1.0, 1.4, 2.0, 2.8, and 4.0 kHz.

MAIN OUTCOME MEASURE

The amount of suppression of the OAE, calculated in half-octave frequency bands.

RESULTS

Otoacoustic emission amplitudes were equal in both groups. Contralateral suppression of the signal was found in both patients and controls. The amount of suppression was equal, except for the 2.0- and 2.8-kHz frequency bands in the right ear (p value of 0.03, 0.008, respectively), for which the patients had less suppression.

CONCLUSION

The suppression of otoacoustic emissions with CAS seems equally effective in tinnitus patients and healthy controls. The minor differences between both groups suggest subtle differences in the function of the medial olivocochlear efferent system.

Characteristics of tinnitus with or without hearing loss: clinical observations in Sicilian tinnitus patients

OBJECTIVE

To analyze the clinical characteristics of tinnitus both in normal hearing subjects and in patients with hearing loss.

METHODS

The study considered 312 tinnitus sufferers, 176 males and 136 females, ranging from 21 to 83 years of age, who were referred to the Audiology Section of the Department of Bio-technology of Palermo University. The following parameters were considered: age, sex, hearing threshold, tinnitus laterality, tinnitus duration, tinnitus measurements and subjective disturbance caused by tinnitus. The sample was divided into two groups: Group 1 (G1) subjects with normal hearing; Group 2 (G2) subjects with hearing loss.

RESULTS

Among the patients considered, 115 have normal hearing while 197 have a hearing deficit. There is a slight predominance of males respect to females that is more evidenced in G2 (61.42% of males vs. 38.58% of females). The highest percentage of tinnitus results in the decades 41-50 for G1 and >70 for G2 with a statistically significant difference between the two groups (P<0.0001). The hearing impairment results in most cases of sensorineural type (74.62%) and limited to the high frequencies (58.50%), moreover the 72.10% of the patients with SNHL had a high-pitched tinnitus while the 88.37% of the patients high-frequency sensorineural hearing loss had a high-pitched tinnitus (P<0.0001). As for the subjective discomfort, the catastrophic category resulted most representative among subjects with normal hearing with a statistically significant difference between the two groups but no significant correlation was found between the level of tinnitus intensity and the tinnitus annoyance confirming the possibility that tinnitus discomfort is elicited by a certain degree of psychological distress as anxiety, depression, irritability and phobias that do not allow the phenomenon of the 'habituation'.

CONCLUSION

This work, according to literature data, suggests that the hearing status and the elderly represent the principal tinnitus related factors; moreover tinnitus characteristics differ in the two groups for tinnitus pitch. There is, in fact, a statistically significant association between high-pitched tinnitus and high-frequency SNHL suggesting that the auditory pathway reorganization induced by hearing loss could be one of the main source of the tinnitus sensation.

Quantitative analysis of cochlear active mechanisms in tinnitus subjects with normal hearing sensitivity: multiparametric recording of evoked otoacoustic emissions and contralateral suppression

OBJECTIVE

Aim of this study was to investigate the possible role played by outer hair cells and cochlear efferent system functionality when tinnitus develops in normal hearing ears. A multiparametric approach was used, entailing recording and analysis of a set of otoacoustic emissions (OAEs): distortion product (DPOAEs), transient evoked (TEOAEs) and efferent-mediated TEOAE suppression in the presence of contralateral acoustic stimulation (CAS).

METHODS

Fifty-four subjects with normal hearing sensitivity participated in the study. Twenty-three suffered from chronic subjective tinnitus whereas thirty-one did not have tinnitus and acted as control subjects. DPOAEs were measured with eliciting tones of frequency ratio 1.22 and intensity 65 and 55dB SPL in the frequency range 0.5-8kHz. TEOAEs were recorded with the 'linear' protocol using clicks at 60dB peak SPL both in the absence and in the presence of CAS at two different intensities. DPOAE amplitude, TEOAE amplitude, and TEOAE suppression were analysed as relevant parameters.

RESULTS

Significantly reduced DPOAE amplitude in the frequency range 1.5-8kHz, lower TEOAE amplitude, and slightly decreased TEOAE suppression were measured in tinnitus subjects compared to non-tinnitus controls. In particular, 74% of tinnitus subjects exhibited abnormal DPOAEs, 13% had abnormal TEOAEs, whereas abnormal TEOAE suppression was found in 9% of patients.

CONCLUSION

Overall, the present work revealed the presence of abnormal OAEs, in particular at higher frequencies, in tinnitus subjects with normal hearing sensitivity. A minor (i.e., sub-clinical) outer hair cell dysfunction, particularly in high-frequency cochlear regions, might thus be assumed in normal hearing tinnitus subjects. In order to better put in light the possible role played by outer hair cells in low-frequency cochlear regions, or by the cochlear efferent system, additional analyses would be needed.

[DPOAE and lateral inhibition in chronic tinnitus]

INTRODUCTION

According to our audiological data, 90% of tinnitus patients have deficits in inner ear function as a generator of tinnitus, mainly in the outer hair cells (OHC). This can be verified by registration of distortion products of otoacoustic emissions (DPOAE). Thus, the main origin of tinnitus is peripheral, and most patients suffer from accompanying hearing loss, even though it is sometimes mild or subjectively not even felt. Whether or not the tinnitus is disturbing, however, is determined through further auditory processing of the "signal" tinnitus and its psychological validation. With almost 50% of our tinnitus and hyperacusis patients, we find hyperfunctioning of the OHC, possibly originating from reduced or ineffective efferent control in the auditory pathway. Efferent activity can be measured by acoustic stimulation of the contralateral ear, which normally reduces the DPOAE amplitudes via efferent inhibition.

METHOD AND PATIENTS

DPOAE were recorded with 67 tinnitus patients (127 ears) with and without contralateral acoustic stimulation. Twenty-one persons (41 ears) served as controls.

RESULTS

With 64% of the tinnitus patients, DPOAE amplitudes were not reduced significantly, compared with 34% of the controls. The medium amplitude reduction for controls was 1.76 dB, whereas for the tinnitus patients it was significantly less (0.91 dB).

CONCLUSION

For a considerable number of tinnitus patients, efferent control of OHC activity is restricted, but this seems to be confined to a certain type of tinnitus only.