Tinnitus in normally hearing patients: clinical aspects and repercussions

Prevalence of tinnitus following non-blast related traumatic brain injury: a systematic review of literature

OBJECTIVES

To establish the prevalence of tinnitus in adults who have sustained non-blast related traumatic brain injury (TBI), as well as the prevalence of tinnitus following TBI in the absence of hearing loss.

METHODS

A systematic search was carried out using MEDLINE, EMBASE, PsycINFO, CINAHL from January 1st 1990 to August 14th 2023. TBI, tinnitus and auditory findings were extracted from all eligible studies, and a descriptive synthesis performed. This systematic review was registered with PROSPERO (Registration number: CRD42022377637).

RESULTS

Based on the Oxford Centre of Evidence-Based Medicine (OCEBM) (2011) criteria, the highest quality evidence identified was at Level 2b, with the bulk of the included studies predominantly populating the lower evidence tiers. While there was a substantial variability in the methods used to establish and report the presence of tinnitus, its occurrence following TBI was evident in adults with and without hearing loss.

CONCLUSION

The need for prospective, longitudinal research into tinnitus following non-blast related TBI is evident. Such comprehensive studies hold the potential to inform and enhance the clinical diagnosis and management of this patient population.

Tinnitus pitch does not always fall within the frequency range of hearing loss - a cross-sectional study on the mechanism of tinnitus production

BACKGROUND

Clinically, we find that tinnitus patients often have hearing loss. According to the most accepted mechanism of tinnitus, that is, the spontaneous discharge and abnormal synchronization of neurons after afferent reduction, tinnitus frequency is closely related to the frequency of hearing loss.

OBJECTIVE

The purpose of this study was to investigate the correlation of tinnitus pitch with the frequency of hearing loss.

MATERIALS AND METHODS

A total of 500 patients with unilateral or bilateral chronic tinnitus were enrolled in this study. All patients underwent pure tone audiometry (PTA) and tinnitus acoustic examination. Hearing loss levels and frequencies were recorded. The relationship between tinnitus pitch and hearing loss level and frequency was statistically analyzed.

RESULTS

Our results showed that 96.6% of the 500 tinnitus patients had hearing loss. Statistical analysis showed that low frequency (LF) tinnitus was correlated with LF hearing loss, but moderate frequency & high frequency (MF&HF) tinnitus was not significantly associated with MF&HF hearing loss. The coincidence of tinnitus pitch with the highest hearing threshold correlated with the degree of hearing loss.

CONCLUSION AND SIGNIFICANCE

The vast majority of patients with chronic subjective tinnitus had hearing loss, and the frequency of tinnitus correlated with the degree and frequency of hearing loss but not exactly fall within the frequency range of hearing loss.

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.

Influence of Bone Conduction Hearing Device Implantation on Health-Related Quality of Life for Patients with and without Tinnitus

(1) Background: Tinnitus, often related to hearing loss, is an addressable public health concern affecting health-related quality of life (HRQoL). This study aimed to explore the influence of bone conduction hearing aid (BCHA) implantation on HRQoL and hearing disability in patients with hearing loss suffering from tinnitus. (2) Methods: Data were collected from an international hearing implant registry. Health Utilities Index Mark 3 (HUI-3), Spatial and Qualities of Hearing- 49 Questionnaire (SSQ) and self-reported tinnitus burden data for adult patients implanted with a BCHA (n = 42) who provided baseline as well as follow-up data 1-year post-implantation were extracted from the registry. Wilcoxon signed rank tests and paired samples t-tests were used to analyse outcomes data. (3) Results: Patients, with or without tinnitus, demonstrated clinically important mean improvements in HUI-3 multi-attribute utility scores, HUI-3 hearing attribute and SSQ scores. Hearing loss patients with tinnitus presented with a lower HRQoL than patients without tinnitus. (4) Conclusions: These findings demonstrate the importance of hearing rehabilitation in improving the quality of life and hearing disability of patients with or without tinnitus and in providing tinnitus relief in some patients with hearing loss and tinnitus.

Relationship Between Tinnitus and Hearing Outcomes Among US Military Personnel After Blast Injury

OBJECTIVES

To examine the association between tinnitus and hearing outcomes among US military personnel after blast injury, including any hearing loss, low-frequency hearing loss, high-frequency hearing loss, early warning shift, and significant threshold shift.

DESIGN

In this retrospective study, the Blast-Related Auditory Injury Database was queried for male military service members who had audiometric data 2 years before and after blast injury between 2004 and 2012 with no history of hearing loss or tinnitus before injury (n = 1693). Tinnitus was defined by diagnostic codes in electronic health records. Multivariable logistic regression examined the association between tinnitus and hearing outcomes, while adjusting for covariates.

RESULTS

Overall, 14.2% (n = 241) of the study sample was diagnosed with tinnitus within 2 years after blast injury. The proportions of all examined hearing outcomes were higher among service members with tinnitus than those without ( p < 0.001). In multivariable analysis, service members with tinnitus had higher adjusted odds of any hearing loss (odds ratio [OR] = 1.72, 95% confidence interval [CI] = 1.20-2.47), low-frequency hearing loss (OR = 2.77, 95% CI = 1.80-4.26), high-frequency hearing loss (OR = 2.15, 95% CI = 1.47-3.16), early warning shift (OR = 1.83, 95% CI = 1.36-2.45), and significant threshold shift (OR = 2.15, 95% CI = 1.60-2.89) compared with service members without tinnitus.

CONCLUSIONS

The findings of this study demonstrate that tinnitus diagnosed within 2 years after blast injury is associated with the examined hearing outcomes in US military personnel. Service members with blast injury who subsequently experience tinnitus should receive routine audiometric hearing conservation testing and be carefully examined for poor hearing outcomes by an audiologist.

A Systematic Review and Meta-Analysis of Extended High-Frequency Hearing Thresholds in Tinnitus With a Normal Audiogram

OBJECTIVES

Current evidence supports the growing application of extended high-frequency (EHF: 9 to 20 kHz) audiometry in hearing research, which likely results from the high vulnerability of this frequency region to damage induced by known auditory risk factors. The present systematic review and meta-analysis were performed to investigate whether adults with a normal audiogram and tinnitus show increased EHF hearing thresholds relative to control peers.

DESIGN

A comprehensive search was undertaken on electronic databases consisting of PubMed, ScienceDirect, Wiley, and Google Scholar using combined keywords: "tinnitus," "extended high frequency," "normal audiogram," and "hidden hearing loss."

RESULTS

From 261 articles found by searching databases, nine studies met the inclusion criteria for the meta-analysis. A significant difference was observed between tinnitus and control groups in the effect size analysis of hearing thresholds at 10, 12.5, 14, 16, and 18 kHz ( p ≤ 0.001), and the I-square heterogeneity analysis was below 50% in all studies ( p ≥ 0.131). Visual inspection by the Funnel plot and Egger's regression test ( p ≥ 0.211) also exhibited no publication bias in the meta-analyses.

CONCLUSIONS

Our findings are in support of the idea that in most cases, tinnitus is associated with some degree of cochlear mechanical dysfunction, which may not be detected by conventional audiometry alone. This finding underscores the significance of EHF audiometry in clinical practice, which may help both early identification of individuals susceptible to developing tinnitus and reduce the number of new cases through preventive counseling programs.

Tinnitus, sound intolerance, and mental health: the role of long-term occupational noise exposure

PURPOSE

Whereas chronic noise exposure (CNE) is a known risk factor for tinnitus, little is known about how a history of CNE impacts tinnitus characteristics and its comorbid symptoms.

METHODS

Seventy-five participants with chronic tinnitus (59m/16f, 22-78 years, 48 with sensory-neural hearing loss, and 27 with a normal audiogram) including 43 individuals with (Tin-CNE group) and 32 without (Tin group) a history of long-term occupational noise exposure were studied. Tinnitus characteristics were rated by a visual analog scale, and tinnitus comorbid symptoms were scored using self-assessment questionnaires.

RESULTS

The Tin-CNE group showed reduced uncomfortable loudness level (ULL), sound tolerance, and quality of life (QoL), and increased tinnitus loudness, tinnitus handicap, anxiety, depression, insomnia severity, and tinnitus annoyance scores compared to the Tin group. Higher tinnitus loudness and a lower anxiety score were observed in participants with hearing loss relative to those without. Using a stepwise regression model also showed that tinnitus-related characteristics, hyperacusis, and tinnitus comorbid symptoms enhance one another.

CONCLUSIONS

The findings were in support of accumulative evidence indicating the adverse auditory and non-auditory effects of CNE, including exacerbated sound intolerance and tinnitus-related psychiatric symptoms. The results also showed that tinnitus alone can affect mental health regardless of hearing loss.

Low Sleep Satisfaction Is Related to High Disease Burden in Tinnitus

Previous studies have shown a high prevalence of sleep disturbances in tinnitus patients. However, no study has yet evaluated subjective sleep satisfaction. The present study aimed to investigate associations of self-reported sleep satisfaction with sociodemographic factors, tinnitus-related distress, depression, and self-reported quality of life. This is a retrospective analysis of 2344 outpatients with tinnitus presenting at a tertiary German tinnitus clinic from 2010 to 2020. Patients who filled in five questionnaires (Tinnitus Handicap Inventory (THI), Tinnitus Questionnaire (TQ), Major Depression Inventory (MDI), Tinnitus Sample Case History Questionnaire (TSCHQ), and the World Health Organization Quality of Life Brief Version (WHOQOL-Bref)) were included. Based on the question about sleep satisfaction in the WHOQOL-Bref, group classification into (I) sleep-satisfied, (II) neither satisfied or dissatisfied, and (III) sleep-dissatisfied patients was performed. Associations between sleep satisfaction and quality of life, depression, tinnitus distress, and tinnitus characteristics were analyzed by group differences and a multinomial regression model with elastic net penalization. A total of 42.38% of patients were satisfied or very satisfied with sleep, whereas 40.91% of patients were dissatisfied or very dissatisfied with sleep. The remaining patients reported being neither satisfied nor dissatisfied with sleep. Sleep-dissatisfied patients were significantly more burdened in questionnaires on depressive symptoms (MDI), tinnitus distress (TQ, THI), and quality of life (WHOQOL-Bref). In addition, they suffered significantly more often from comorbidities such as headache, neck pain, or temporomandibular joint disorder (TMJ). The elastic net regression based on sum scores of THI, TQ, MDI, the four domains of WHOQOL-Bref, as well as all individual questions from the TSCHQ was able to classify patients satisfied with their sleep with an accuracy of 79%, 87.8% sensitivity, and 70.4% specificity. The model could not identify patients indifferent with the quality of their sleep (neither satisfied nor dissatisfied) (sensitivity: 0%; specificity: 100%). The accuracy of the model to predict patients dissatisfied with their sleep was 80.7%, with 83% sensitivity and 78.4% specificity. Poor physical and mental health (Domain I/II WHOQOL-Bref) as well as tinnitus distress were the strongest predictors of sleep dissatisfaction. Conversely, for sleep satisfaction, good physical and mental health as well as low tinnitus distress were the strongest predictors. The division into sleep-satisfied and sleep-dissatisfied tinnitus patients allows a very good discrimination regarding disease burden as indicated by depression, tinnitus distress, quality of life, and pain-related comorbidities. Physical and mental health as well as tinnitus distress seem to be strongly related to sleep satisfaction underscoring the concept of "tinnitus" versus "tinnitus disorder", but also the importance of sleep satisfaction as a global health indicator. Moreover, these data indicate the relevance of addressing sleep disorders in the therapeutic management of chronic tinnitus patients.

Hearing Aids Mitigate Tinnitus, But Does It Matter if the Patient Receives Amplification in Accordance With Their Hearing Impairment or Not? A Meta-Analysis

PURPOSE

The purpose of the present meta-analysis is to explore the potential effects of objective verification of hearing aid amplification on tinnitus-related outcomes.

METHOD

Twenty-seven studies reporting tinnitus outcomes pre and post hearing aid fitting were identified through a systematic literature search. From these studies, data from 1,400 participants were included in the present meta-analysis. Studies were divided into subgroups based on whether they had reported performing objective verification of the participants' hearing aid amplification or not. Outcome measures were tinnitus distress and tinnitus loudness.

RESULTS

Meta-analyses of all included studies indicated verified amplification to result in significantly enhanced reduction of tinnitus loudness (p < .00001), while the enhanced reduction of tinnitus distress only approached statistical significance (p = .07). However, when excluding an outlier from the subgroup of studies using unverified amplification, individuals receiving verified amplification showed significantly greater reduction of tinnitus distress (p = .02). In addition, analyses of longitudinal effects revealed that the reductions of tinnitus distress decreased over time among individuals receiving unverified amplification but increased over time among individuals receiving verified amplification.

CONCLUSIONS

The present meta-analysis indicates verified hearing aid amplification to be superior to unverified amplification in terms of reduction of tinnitus loudness and distress. The longitudinal increase of mitigation of tinnitus distress with verified amplification only may reflect improved neural reorganization and/or better adherence to hearing aid use, with verified compared to unverified amplification. Due to the low cost of hearing aid verification compared to the high societal cost of tinnitus, objective verification of hearing aid amplification for tinnitus patients is recommended.

Extended High Frequency Hearing, but Not Tinnitus, Is Associated With Every-Day Cognitive Performance

Research into the potential associations between tinnitus and cognition has investigated specific cognitive domains in laboratory settings despite adults with tinnitus reporting broad cognitive difficulties in every-day life. To address this limitation, the present study compared performance and perceived exertion on a visual office-like task in 38 adults with tinnitus (19 with normal hearing and 19 with hearing loss) and 38 adults without tinnitus (19 with normal hearing and 19 with hearing loss) matched for age, sex and educational background. All participants were also assessed for hearing, anxiety and depression, and participants with tinnitus were also assessed for tinnitus handicap. No associations were found between presence of tinnitus and cognitive performance (mean total rate correct score on the visual office-like task being 2.9 for the tinnitus group, 2.8 for the control group, p = 0.612) and perceived exertion (mean ratings of perceived exertion on the Borg CR10-scale being 5.8 for the tinnitus group, 6.5 for the control group, p = 0.063) on the visual office-like task when corrected for standard (0.125 to 8 kHz) and extended high frequency (10 to 16 kHz) hearing thresholds, anxiety, and depression. The correction for extended high frequency average (10, 12.5, 14, and 16 kHz) hearing threshold was significant for performance (p = 0.009) but not perceived exertion on the visual office-like task. Overall, the results showed extended high frequency hearing, but not tinnitus, was associated with every-day cognitive performance. This indicates clinical testing of hearing thresholds above 8 kHz could support clinicians' identification and management of cognitive difficulties. One management method suggested by the current findings would include provision of auditory stimulation at frequencies exceeding the frequency response of many current hearing aids.

Optimizing non-invasive functional markers for cochlear deafferentation based on electrocochleography and auditory brainstem responses

Accumulating evidence suggests that cochlear deafferentation may contribute to suprathreshold deficits observed with or without elevated hearing thresholds, and can lead to accelerated age-related hearing loss. Currently there are no clinical diagnostic tools to detect human cochlear deafferentation in vivo. Preclinical studies using a combination of electrophysiological and post-mortem histological methods clearly demonstrate cochlear deafferentation including myelination loss, mitochondrial damages in spiral ganglion neurons (SGNs), and synaptic loss between inner hair cells and SGNs. Since clinical diagnosis of human cochlear deafferentation cannot include post-mortem histological quantification, various attempts based on functional measurements have been made to detect cochlear deafferentation. So far, those efforts have led to inconclusive results. Two major obstacles to the development of in vivo clinical diagnostics include a lack of standardized methods to validate new approaches and characterize the normative range of repeated measurements. In this overview, we examine strategies from previous studies to detect cochlear deafferentation from electrocochleography and auditory brainstem responses. We then summarize possible approaches to improve these non-invasive functional methods for detecting cochlear deafferentation with a focus on cochlear synaptopathy. We identify conceptual approaches that should be tested to associate unique electrophysiological features with cochlear deafferentation.

Detecting Noise-Induced Cochlear Synaptopathy by Auditory Brainstem Response in Tinnitus Patients With Normal Hearing Thresholds: A Meta-Analysis

Noise-induced cochlear synaptopathy (CS) is defined as a permanent loss of synapses in the auditory nerve pathway following noise exposure. Several studies using auditory brainstem response (ABR) have indicated the presence of CS and increased central gain in tinnitus patients with normal hearing thresholds (TNHT), but the results were inconsistent. This meta-analysis aimed to review the evidence of CS and its pathological changes in the central auditory system in TNHT. Published studies using ABR to study TNHT were reviewed. PubMed, EMBASE, and Scopus databases were selected to search for relevant literature. Studies (489) were retrieved, and 11 were included for meta-analysis. The results supported significantly reduced wave I amplitude in TNHT, whereas the alternations in wave V amplitude were inconsistent among the studies. Consistently increased V/I ratio indicated noise-induced central gain enhancement. The results indicated the evidence of noise-induced cochlear synaptopathy in tinnitus patients with normal hearing. However, inconsistent changes in wave V amplitude may be explained by that the failure of central gain that triggers the pathological neural changes in the central auditory system and/or that increased central gain may be necessary to generate tinnitus but not to maintain tinnitus.

The Relationship Between Tinnitus Pitch, Audiogram Edge Frequency, and Auditory Stream Segregation Abilities in Individuals With Tinnitus

Purpose Around 80%-93% of the individuals with tinnitus have hearing loss. Researchers have found that tinnitus pitch was related to the frequencies of hearing loss, but unclear about the relationship between tinnitus pitch and audiometry edge frequency. The comorbidity of tinnitus and speech perception in noise problems had also been reported, but the relationship between tinnitus pitch and speech perception in noise had seldom been investigated. This study was designed to estimate the relationship between tinnitus pitch, audiogram edge frequency, and speech perception in noise. The speech perception in noise was measured using auditory stream segregation paradigm. Method Thirteen individuals with bilateral mild-to-severe tonal tinnitus and minimal-to-mild cochlear hearing loss were selected. Thirteen individuals with hearing loss without tinnitus were also selected. The audiogram of each participant with tinnitus was matched with that of the participant without tinnitus. Tinnitus pitch of the participants with tinnitus was measured and compared with audiogram edge frequency. The stream segregation thresholds were calculated at the participants' admitted tinnitus pitch and one octave below the tinnitus pitch. The stream segregation thresholds were estimated at fission and fusion boundary using pure-tone stimuli in ABA paradigm. Results High correlation between tinnitus pitch and audiogram edge frequency was noted. Overall stream segregation thresholds were higher for individuals with tinnitus. Higher thresholds indicated poorer stream segregation abilities. Within tinnitus participants, the thresholds were significantly lesser at frequency corresponding to admitted tinnitus pitch than at one octave below the tinnitus pitch. Conclusions The information from this study may be helpful in educating the patients about the relationship between hearing loss and tinnitus. The findings may also account for speech-perception-in-noise difficulties often reported by the individuals with tinnitus.

Evaluation of Vestibulo-Ocular Reflex (VOR) in Tinnitus Patients with Normal Hearing

OBJECTIVES

This study aimed to evaluate the correlation between tinnitus parameters (duration, severity, reaction, handicap levels) and vestibulo-ocular reflex (VOR) gain values in patients with tinnitus with normal hearing without vertigo or any other complaints and to compare the VOR gains with a healthy group.

MATERIALS AND METHODS

The study group consisted of 30 individuals aged between 18 and 65 years who suffered from tinnitus but not from hearing loss and vertigo. The control group also consisted of 30 individuals who were categorized as healthy adults. The tinnitus handicap inventory, tinnitus reaction questionnaire, and tinnitus handicap questionnaire were applied to each individual in the tinnitus group, and the video head impulse test (VHIT) was conducted in 2 groups.

RESULTS

Statistically, a significant difference was found between the 2 groups in terms of VOR gain values in horizontal and vertical semicircular canal planes (p<0.05). However, there was no statistically significant correlation between tinnitus parameters, age, and VOR gain values in the study group (p>0.05).

CONCLUSION

Considering the lower VOR gain values of the study group than the control group, these patients may need to be followed up for vestibular dysfunction associated with tinnitus, which can be a symptom of peripheral vestibular disorder. Moreover, this study will contribute to the literature because we determined a high-frequency component of VOR by VHIT, which was used to evaluate the relationship between tinnitus parameters and peripheral vestibular function.

[Assessing ear noise in expert opinion: Possibility, plausibility and probability]

Tinnitus as a subjective, individual sensation defies objective proof. In the assessment situation, tinnitus must also be distinguished from physiological or spontaneous hearing sensations.With regard to the new German "Königsteiner Recommendation" and the verdicts of the last few years, against the background of the different concepts of causality in the statutory and private accident insurance, a stringent examination to determine whether there is a sufficiently high probability of an accident-related subjective ear noise is necessary in the assessment. In order to create a comprehensible and comparable basis, the proposal of a plausibility check with the recording of 5 criteria - appropriate event, immediacy, reproducibility on the basis of today's examination methods of tinnitus masking and matching, persistence and fixation and the recording with a non-suggestive question was subjected to a review.The review shows that the requirements for the respective standard of proof can be fulfilled with the given steps of proof. The simple possibility of the presence of ringing in the ears can be systematically led to the probability of the presence by means of the plausibility criteria, which include psychoacoustic procedures, as well as open questions. This creates the prerequisites for a comprehensible causal consideration between the event and the reported tinnitus according to current medical-scientific knowledge.

Evidence of Cochlear Synaptopathy and the Effect of Systemic Steroid in Acute Idiopathic Tinnitus With Normal Hearing

OBJECTIVE

To evaluate the electrophysiologic evidence of cochlear synaptopathy and the effects of systemic steroids in acute idiopathic tinnitus with normal hearing.

STUDY DESIGN

Retrospective review of medical data.

SETTING

Tertiary referral center.

PATIENTS

Fifty-nine patients who experienced acute-onset idiopathic tinnitus (within 12 weeks) with normal hearing and the same number of age- and pure-tone threshold-matched control groups.

INTERVENTION

Electrophysiologic studies of the auditory pathway, oral steroids, and ginkgo biloba.

MAIN OUTCOME MEASURES

Pure-tone thresholds, wave I and wave V amplitudes of the auditory brainstem response (ABR), tinnitus handicap inventory (THI), and visual analog scale (VAS).

RESULTS

Significantly reduced ABR wave I amplitude and wave I/wave V ratio were found in the tinnitus group compared with the no tinnitus group. Age and pure-tone threshold were significantly correlated with reduced wave I amplitude and small wave I/wave V ratio. The THI and VAS scores were decreased at 3 and 12 weeks after steroid administration; however, overall changes in THI and VAS scores were not significantly different between the steroid and ginkgo biloba groups.

CONCLUSION

Potential cochlear synaptopathy was suspected in the early stage of acute idiopathic tinnitus, even in patients with normal hearing. Age and hearing threshold were potentially associated with the development of cochlear synaptopathy. Low-dose oral steroids and ginkgo biloba induced early subjective relief of tinnitus, which maintained up to 12 weeks, however, those changes did not differ between groups.

On the impairment of executive control of attention in chronic tinnitus: Evidence from the attention network test

Subjective, chronic tinnitus is a condition that is common in most populations. Whereas many individuals tend to habituate to tinnitus over time, for some their attention seems pathologically drawn towards the sensation. For this subgroup of individuals with severe tinnitus, dysfunctional executive attention has been suggested to be implicated in the failure to habituate. However, since most previous studies have used attention tests with low validity and specificity in this assessment, there is a need for further corroborating studies. In the present study, the Attention Network Test was used to compare mainly the efficiency of executive attention between a group of individuals with chronic tinnitus (TG; n = 33) and a healthy control group (CG; n = 37). The results showed that individuals with chronic tinnitus, compared to the CG, did not present with a specific impairment in executive control of attention, nor in any of the other two attention domains. These findings are discussed in relation to the sampling characteristics in this study, which might have led to the sample being more homogenous and high functioning than samples in tinnitus studies generally. Overall, this study suggests that tinnitus and executive control of attention impairment might not be directly related, and that the latter might not necessarily be associated with the maintenance of the condition.

Loud Music and Leisure Noise Is a Common Cause of Chronic Hearing Loss, Tinnitus and Hyperacusis

High sound levels capable of permanently damaging the ear are experienced not only in factories and war zones but in concert halls, nightclubs, sports stadiums, and many other leisure environments. This review summarizes evidence that loud music and other forms of "leisure noise" are common causes of noise-induced hearing loss, tinnitus, and hyperacusis, even if audiometric thresholds initially remain within clinically normal limits. Given the huge global burden of preventable noise-induced hearing loss, noise limits should be adopted in a much broader range of settings, and education to promote hearing conservation should be a higher public health priority.

What's the buzz? The neuroscience and the treatment of tinnitus

Tinnitus is a pervasive public health issue that affects ∼15% of the United States population. Similar estimates have also been shown on a global scale, with similar prevalence found in Europe, Asia, and Africa. The severity of tinnitus is heterogeneous, ranging from mildly bothersome to extremely disruptive. In the United States, ∼10-20% of individuals who experience tinnitus report symptoms that severely reduce their quality of life. Due to the huge personal and societal burden, in the last 20 yr a concerted effort on basic and clinical research has significantly advanced our understanding and treatment of this disorder. Yet, neither full understanding, nor cure exists. We know that tinnitus is the persistent involuntary phantom percept of internally generated nonverbal indistinct noises and tones, which in most cases is initiated by acquired hearing loss and maintained only when this loss is coupled with distinct neuronal changes in auditory and extra-auditory brain networks. Yet, the exact mechanisms and patterns of neural activity that are necessary and sufficient for the perceptual generation and maintenance of tinnitus remain incompletely understood. Combinations of animal model and human research will be essential in filling these gaps. Nevertheless, the existing progress in investigating the neurophysiological mechanisms has improved current treatment and highlighted novel targets for drug development and clinical trials. The aim of this review is to thoroughly discuss the current state of human and animal tinnitus research, outline current challenges, and highlight new and exciting research opportunities.

Noise: Acoustic Trauma to the Inner Ear

Cochlear damage is often thought to result in hearing thresholds shift, whether permanent or temporary. The report of tinnitus in the absence of any clear deficit in cochlear function was believed to indicate that hearing loss and tinnitus, while comorbid, could arise independently from each other. In all likelihood, tinnitus that is not of central nervous system origin is associated with hearing loss. As a correlate, although a treatment of most forms of tinnitus will likely emerge in the years to come, curing tinnitus will first require curing hearing loss.

Objective Verification of Acute Tinnitus and Validation of Efficacy of Systemic Steroids in Rats

BACKGROUND

This study was performed to identify acute tinnitus and evaluate the efficacy of steroids for noise-induced acute tinnitus by measuring the gap-prepulse inhibition of the acoustic startle (GPIAS) value in an animal model.

METHODS

Nineteen rats (the noise group [n = 7] and the noise + dexamethasone [DEX] group [n = 12]) were exposed to narrow-band noise centered at 16 kHz from a sound generator for 4 hours. The noise + DEX group received intraperitoneal steroid administration daily for 5 days (1.5 mg/kg/day) after completing noise exposure. Auditory brainstem response and GPIAS value were measured just prior to, and 1 day after noise exposure and on days 1 and 10 days after completing steroid administration. The changes in cochlear structure were evaluated by histological analysis.

RESULTS

The threshold shift was checked 1 and 10 days after intraperitoneal steroid injection, and no differences in threshold shift were observed between the two groups in each frequency except for 32 kHz 1 day after steroid injection. The mean GPIAS value in the noise + DEX group (36.4% ± 14.1%) was significantly higher than that in the noise group (16.4% ± 18.8%) 10 days after intraperitoneal steroid administration (P = 0.017). There were no pathological changes associated with noise trauma in the two groups as determined on hematoxylin and eosin and immunohistochemical staining.

CONCLUSION

An acute tinnitus model with minimal structural changes by noise exposure was set up, and used to verify tinnitus objectively by measuring the GPIAS value. Steroid therapy for control of tinnitus was validated in this animal model.

Functional Impact of Tinnitus in Patients with Hearing Loss

Introduction  Tinnitus, which is considered the third worst symptom for humans, is a common complaint among people living with hearing loss and may negatively affect the quality of life of those who have it. Objective  To analyze the perception of the handicap in patients with tinnitus and hearing loss as well as the possible associations between the variables hearing loss, loudness, onset, frequency and annoyance by tinnitus, and the correlation between the visual analogue scale (VAS) and the Tinnitus Handicap Inventory (THI). Methods  A total of 30 patients with complaints of tinnitus and the presence of sensorineural hearing impairment were selected for this cross-sectional, observational, and descriptive study. The loudness of the tinnitus was measured by a VAS and classified as mild, moderate, or severe. The THI was classified as slight, mild, moderate, severe, and catastrophic. Data were submitted to statistical analysis using the Fisher exact test and Spearman correlation coefficient. Results  Eleven male (36.7%) and 19 female (63.3%) subjects with a mean age of 56.5 years old were evaluated. There was no significant association between loudness, annoyance, time and frequency of tinnitus, nor between hearing loss and tinnitus. There was a significant association between the variables hearing loss and loudness, and a weak correlation between VAS and THI. Conclusion  Tinnitus has a practical impact in the lives of patients with hearing loss in terms of catastrophic, functional, and emotional aspects, regardless of loudness, frequency, or time of onset. Hearing loss was a factor that had an impact on the loudness of tinnitus. There was no statistically significant correlation between VAS and THI.

The Magnitude and Determinants of Tinnitus among Health Science Students at King Khalid University

BACKGROUND

Tinnitus is a symptom that is defined as a subjective perception of noise in an absence of external sound. It is an indicator of auditory system abnormalities. It can also be present in individuals without any hearing abnormalities. Difficulty to consternate, insomnia, and decreased speech discrimination are the most common symptoms related to tinnitus.

AIM

To assess the magnitude and pattern with determinants of tinnitus among health science students at King Khalid University. Methodology. A descriptive cross-sectional survey was conducted targeting all accessible students in health science colleges in King Khalid University which is the main university in the Aseer region, south of Saudi Arabia. Students were included consecutively from different faculties and different grades. Data were collected through a self-administered prestructured questionnaire, which was distributed and recollected the next day. Tinnitus was screened using an adapted form of the National Health and Nutrition Examination Survey (NHANES).

RESULTS

A total sample of 400 students have been included with their ages ranging from 18 to 30 years with a mean age of 22 ± 1.8 years), and 28.5% of the students recorded positive findings. Tinnitus was bilateral among 51.8% of students, and 44.7% of tinnitus students hear buzzing sound while 21.1% have hissing sound and 10.5% had pulsating sound. Among 46.5% of students with tinnitus, the heard sound was of moderate loudness and intermittent among 64.9% of them. Conclusions and Recommendations. In conclusion, the study revealed that just more than a quarter of students complained of tinnitus which was bilateral among half of them. Tinnitus frequency was mainly moderate in intensity and intermittent. Having ear problems, loud sounds, and allergy were the most important predictors of having Tinnitus.

Aging and Central Auditory Disinhibition: Is It a Reflection of Homeostatic Downregulation or Metabolic Vulnerability?

Aging-related changes have been identified at virtually every level of the central auditory system. One of the most common findings across these nuclei is a loss of synaptic inhibition with aging, which has been proposed to be at the heart of several aging-related changes in auditory cognition, including diminished speech perception in complex environments and the presence of tinnitus. Some authors have speculated that downregulation of synaptic inhibition is a consequence of peripheral deafferentation and therefore is a homeostatic mechanism to restore excitatory/inhibitory balance. As such, disinhibition would represent a form of maladaptive plasticity. However, clinical data suggest that deafferentation-related disinhibition tends to occur primarily in the aged brain. Therefore, aging-related disinhibition may, in part, be related to the high metabolic demands of inhibitory neurons relative to their excitatory counterparts. These findings suggest that both deafferentation-related maladaptive plastic changes and aging-related metabolic factors combine to produce changes in central auditory function. Here, we explore the arguments that downregulation of inhibition may be due to homeostatic responses to diminished afferent input vs. metabolic vulnerability of inhibitory neurons in the aged brain. Understanding the relative importance of these mechanisms will be critical for the development of treatments for the underlying causes of aging-related central disinhibition.

Why Is There No Cure for Tinnitus?

Tinnitus is unusual for such a common symptom in that there are few treatment options and those that are available are aimed at reducing the impact rather than specifically addressing the tinnitus percept. In particular, there is no drug recommended specifically for the management of tinnitus. Whilst some of the currently available interventions are effective at improving quality of life and reducing tinnitus-associated psychological distress, most show little if any effect on the primary symptom of subjective tinnitus loudness. Studies of the delivery of tinnitus services have demonstrated considerable end-user dissatisfaction and a marked disconnect between the aims of healthcare providers and those of tinnitus patients: patients want their tinnitus loudness reduced and would prefer a pharmacological solution over other modalities. Several studies have shown that tinnitus confers a significant financial burden on healthcare systems and an even greater economic impact on society as a whole. Market research has demonstrated a strong commercial opportunity for an effective pharmacological treatment for tinnitus, but the amount of tinnitus research and financial investment is small compared to other chronic health conditions. There is no single reason for this situation, but rather a series of impediments: tinnitus prevalence is unclear with published figures varying from 5.1 to 42.7%; there is a lack of a clear tinnitus definition and there are multiple subtypes of tinnitus, potentially requiring different treatments; there is a dearth of biomarkers and objective measures for tinnitus; treatment research is associated with a very large placebo effect; the pathophysiology of tinnitus is unclear; animal models are available but research in animals frequently fails to correlate with human studies; there is no clear definition of what constitutes meaningful change or "cure"; the pharmaceutical industry cannot see a clear pathway to distribute their products as many tinnitus clinicians are non-prescribing audiologists. To try and clarify this situation, highlight important areas for research and prevent wasteful duplication of effort, the British Tinnitus Association (BTA) has developed a Map of Tinnitus. This is a repository of evidence-based tinnitus knowledge, designed to be free to access, intuitive, easy to use, adaptable and expandable.

Dynamic Changes of Functional Neuronal Activities Between the Auditory Pathway and Limbic Systems Contribute to Noise-Induced Tinnitus with a Normal Audiogram

Tinnitus is thought to be triggered by aberrant neural activity in the central auditory pathway and is often accompanied by comorbidities of emotional distress and anxiety, which imply maladaptive functional connectivity to limbic structures, such as the amygdala and hippocampus. Tinnitus patients with normal audiograms can also have accompanying anxiety and depression, clinically. To test the role of functional connectivity between the central auditory pathway and limbic structures in patients with tinnitus with normal audiograms, we developed a murine noise-induced tinnitus model with a temporary threshold shift (TTS). Tinnitus mice exhibited reduced auditory brainstem response wave I amplitude, and an enhanced wave IV amplitude and wave IV/I amplitude ratio, as compared with control and non-tinnitus mice. Resting-state functional magnetic resonance imaging (fMRI) was used to identify abnormal connectivity of the amygdala and hippocampus and to determine the relationship with tinnitus characteristics. We found increased fMRI responses with amplitude of low-frequency fluctuation (ALFF) in the auditory cortex and decreased ALFF in the amygdala and hippocampus at day 1, but decreased ALFF in the auditory cortex and increased ALFF in the amygdala at day 28 post-noise exposure in tinnitus mice. Decreased functional connectivity between auditory brain regions and limbic structures was demonstrated at day 28 in tinnitus mice. Therefore, aberrant neural activities in tinnitus mice with TTS involved not only the central auditory pathway, but also limbic structures, and there was maladaptive functional connectivity between the central auditory pathway and limbic structures, such as the amygdala and hippocampus.

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

OBJECTIVES

To determine whether auditory brainstem response (ABR) wave I amplitude is associated with measures of auditory perception in young people with normal distortion product otoacoustic emissions (DPOAEs) and varying levels of noise exposure history.

DESIGN

Tinnitus, loudness tolerance, and speech perception ability were measured in 31 young military Veterans and 43 non-Veterans (19 to 35 years of age) with normal pure-tone thresholds and DPOAEs. Speech perception was evaluated in quiet using Northwestern University Auditory Test (NU-6) word lists and in background noise using the words in noise (WIN) test. Loudness discomfort levels were measured using 1-, 3-, 4-, and 6-kHz pulsed pure tones. DPOAEs and ABRs were collected in each participant to assess outer hair cell and auditory nerve function.

RESULTS

The probability of reporting tinnitus in this sample increased by a factor of 2.0 per 0.1 µV decrease in ABR wave I amplitude (95% Bayesian confidence interval, 1.1 to 5.0) for males and by a factor of 2.2 (95% confidence interval, 1.0 to 6.4) for females after adjusting for sex and DPOAE levels. Similar results were obtained in an alternate model adjusted for pure-tone thresholds in addition to sex and DPOAE levels. No apparent relationship was found between wave I amplitude and either loudness tolerance or speech perception in quiet or noise.

CONCLUSIONS

Reduced ABR wave I amplitude was associated with an increased risk of tinnitus, even after adjusting for DPOAEs and sex. In contrast, wave III and V amplitudes had little effect on tinnitus risk. This suggests that changes in peripheral input at the level of the inner hair cell or auditory nerve may lead to increases in central gain that give rise to the perception of tinnitus. Although the extent of synaptopathy in the study participants cannot be measured directly, these findings are consistent with the prediction that tinnitus may be a perceptual consequence of cochlear synaptopathy.

Mobile Apps for Management of Tinnitus: Users' Survey, Quality Assessment, and Content Analysis

Background

Tinnitus is the perception of a sound without any outside source. It affects 6 million people in the United Kingdom. Sound therapy is a core component of many tinnitus management programs. Potential mechanisms of benefit include making tinnitus less noticeable, habituation, distracting attention from tinnitus, relaxation, and promoting neuroplastic changes within the brain. In recent years, there has been a substantial increase in the use of mobile technology. This provided an additional medium through which people with tinnitus can access different tinnitus management options, including sound therapy.

Objective

The aim of this study was to (1) generate the list of apps that people use for management of their tinnitus, (2) explore reasons for app use and nonuse, (3) perform quality assessment of the most cited apps, and (4) perform content analysis to explore and describe options and management techniques available in the most cited apps.

Methods

A Web-based survey consisting of 33 open and closed questions captured (1) demographic information, information about tinnitus, and hearing loss and (2) mobile app–specific information about the motivation to use an app, the apps which respondents used for tinnitus, important factors when choosing an app, devices used to access apps, and reasons for not using apps. The quality of the most cited apps was assessed using the Mobile Apps Rating Scale (MARS). Content and features of the most cited apps were analyzed.

Results

Data from 643 respondents were analyzed. The majority of respondents (482/643, 75.0%) had never used an app for management of tinnitus mainly because of lack of awareness (381/643, 59.3%). The list of the 55 apps that people use for their tinnitus was generated. These included apps that were developed specifically for the management of tinnitus; however, the majority of cited apps were developed for other problems (eg, sleep, depression or anxiety, and relaxation). Quality assessment of the 18 most popular apps using MARS resulted in a range of mean scores from 1.6 to 4.2 (out of 5). In line with the current model of tinnitus management, sound was the main focus of the majority of the apps. Other components included relaxation exercises, elements of cognitive behavioral therapy, information and education, and hypnosis.

Conclusions

People used apps for the management of their tinnitus; however, this was done mostly as a self-help option, without conjunction with management provided by hearing health care professionals. Further research should consider the place for apps in tinnitus management (stand-alone self-management intervention vs part of the management by a hearing professional). As the content of the apps varies with respect to sound options, information, and management strategies, it seems that the choice of the best management app should be guided by individual patient’s needs and preferences.

Association Between Residual Inhibition and Neural Activity in Patients with Tinnitus: Protocol for a Controlled Within- and Between-Subject Comparison Study

Background

Electroencephalography (EEG) studies indicate possible associations between tinnitus and changes in the neural activity. However, inconsistent results require further investigation to better understand such heterogeneity and inform the interpretation of previous findings.

Objective

This study aims to investigate the feasibility of EEG measurements as an objective indicator for the identification of tinnitus-associated neural activities.

Methods

To reduce heterogeneity, participants served as their own control using residual inhibition (RI) to modulate the tinnitus perception in a within-subject EEG study design with a tinnitus group. In addition, comparison with a nontinnitus control group allowed for a between-subjects comparison. We will apply RI stimulation to generate tinnitus and nontinnitus conditions in the same subject. Furthermore, high-frequency audiometry (up to 13 kHz) and tinnitometry will be performed.

Results

This work was funded by the Infrastructure Grant of the University of Bern, Bern, Switzerland and Bernafon AG, Bern, Switzerland. Enrollment for the study described in this protocol commenced in February 2018. Data analysis is currently under way and the first results are expected to be submitted for publication in 2019.

Conclusions

This study design helps in comparing the neural activity between conditions in the same individual, thereby addressing a notable limitation of previous EEG tinnitus studies. In addition, the high-frequency assessment will help to analyze and classify tinnitus symptoms beyond the conventional clinical standard.

International Registered Report Identifier (IRRID)

RR1-10.2196/12270

An Examination of the Relationship Between Insomnia and Tinnitus: A Review and Recommendations

Tinnitus is a prevalent medical disorder which frequently becomes chronic and severe. Furthermore, quality of life can become compromised with many experiencing comorbid insomnia. We hypothesize that insomnia is a highly prevalent symptom and diagnostic category accompanying tinnitus. Our article reviews the tinnitus literature examining the prevalence of insomnia, the sleep disturbances found, and any methodological issues. Our literature search included a number of databases such as PubMed, Cochrane, and Embase. We found that 16 prior studies had sufficient data presented that allowed for an assessment of the prevalence rate of insomnia in tinnitus; the prevalence rate ranged from 10% to 80% (most rates were over 40%). The overwhelming majority of these studies inadequately defined insomnia as a diagnosis but described it only as a symptom. They focused predominantly on questionnaires (sent via the mail) asking only 1 to 4 questions on whether tinnitus disturbs sleep. Frequently, the only question asked was whether tinnitus disturbed a patient’s sleep without clarifying whether there were problems with daytime functioning. Thus, a valid insomnia diagnosis could not be established. Even in the few studies that asked the necessary information to establish a diagnosis of insomnia, only 1 study provided it. The presence of insomnia in tinnitus was associated with a more severe form of tinnitus. Alarmingly, insomnia was mainly untreated despite evidence supporting that successful treatment of insomnia might also help comorbid tinnitus. Because insomnia is significantly prevalent in tinnitus patients and appears to potentially further impact negatively on one’s quality of life, clinicians should address this possibility with a detailed clinical evaluation; incorporating self-rating questionnaires on sleep could be clinically helpful. If insomnia is present, therapy should be considered.

Tinnitus and sound intolerance: evidence and experience of a Brazilian group

Introduction

Tinnitus and sound intolerance are frequent and subjective complaints that may have an impact on a patient's quality of life.

Objective

To present a review of the salient points including concepts, pathophysiology, diagnosis and approach of the patient with tinnitus and sensitivity to sounds.

Methods

Literature review with bibliographic survey in LILACS, SciELO, Pubmed and MEDLINE database. Articles and book chapters on tinnitus and sound sensitivity were selected. The several topics were discussed by a group of Brazilian professionals and the conclusions were described.

Results

The prevalence of tinnitus has increased over the years, often associated with hearing loss, metabolic factors and inadequate diet. Medical evaluation should be performed carefully to guide the request of subsidiary exams. Currently available treatments range from medications to the use of sounds with specific characteristics and meditation techniques, with variable results.

Conclusion

A review on tinnitus and auditory sensitivity was presented, allowing the reader a broad view of the approach to these patients, based on scientific evidence and national experience.

Weak Middle-Ear-Muscle Reflex in Humans with Noise-Induced Tinnitus and Normal Hearing May Reflect Cochlear Synaptopathy

Chronic tinnitus is a prevalent hearing disorder, and yet no successful treatments or objective diagnostic tests are currently available. The aim of this study was to investigate the relationship between the presence of tinnitus and the strength of the middle-ear-muscle reflex (MEMR) in humans with normal and near-normal hearing. Clicks were used as test stimuli to obtain a wideband measure of the effect of reflex activation on ear-canal sound pressure. The reflex was elicited using a contralateral broadband noise. The results show that the reflex strength is significantly reduced in individuals with noise-induced continuous tinnitus and normal or near-normal audiometric thresholds compared with no-tinnitus controls. Due to a shallower growth of the reflex strength in the tinnitus group, the difference between the two groups increased with increasing elicitor level. No significant difference in the effect of tinnitus on the strength of the middle-ear muscle reflex was found between males and females. The weaker reflex could not be accounted for by differences in audiometric hearing thresholds between the tinnitus and control groups. Similarity between our findings in humans and the findings of a reduced middle-ear muscle reflex in noise-exposed animals suggests that noise-induced tinnitus in individuals with clinically normal hearing may be a consequence of cochlear synaptopathy, a loss of synaptic connections between inner hair cells (IHCs) in the cochlea and auditory-nerve (AN) fibers that has been termed hidden hearing loss.

An economic evaluation of the healthcare cost of tinnitus management in the UK

Background

There is no standard treatment pathway for tinnitus patients in the UK. Possible therapies include education and reassurance, cognitive behavioural therapies, modified tinnitus retraining therapy (education and sound enrichment), or amplification of external sound using hearing aids. However, the effectiveness of most therapies is somewhat controversial. As health services come under economic pressure to deploy resources more effectively there is an increasing need to demonstrate the value of tinnitus therapies, and how value may be continuously enhanced. The objective of this project was to map out existing clinical practice, estimate the NHS costs associated with the management approaches used, and obtain initial indicative estimates of cost-effectiveness.

Methods

Current treatment pathways, costs and health outcomes were determined from the tinnitus literature, national statistics, a patient survey, and expert opinion. These were used to create an Excel-based economic model of therapy options for tinnitus patients. The probabilities associated with the likelihood of an individual patient receiving a particular combination of therapies was used to calculate the average cost of treatment per patient, average health outcome per patient measured in QALYs gained, and cost-effectiveness, measured by the average cost per QALY gained.

Results

The average cost of tinnitus treatment per patient per year is GB£717, equating to an NHS healthcare bill of GB£750 million per year. Across all pathways, tinnitus therapy costs £10,600 per QALY gained. Results were relatively insensitive to restrictions on access to cognitive behaviour therapy, and a subsequent reliance on other therapies.

Conclusions

NHS provisions for tinnitus are cost-effective against the National Institute for Health and Care Excellence cost-effective threshold. Most interventions help, but education alone offers very small QALY gains. The most cost-effective therapies in the model were delivered within audiology.

Electronic supplementary material

The online version of this article (doi:10.1186/s12913-017-2527-2) contains supplementary material, which is available to authorized users.

Assessing Auditory Processing Deficits in Tinnitus and Hearing Impaired Patients with the Auditory Behavior Questionnaire

Background and Purpose: Auditory processing disorders (APD), tinnitus and hearing loss (HL) are typical issues reported by patients in audiologic clinics. These auditory impairments can be concomitant or mutually excluding. APD are not necessarily accompanied by significant HL, whereas many adults exhibit peripheral HL and typical cognitive deficits often associated with APD. Since HL, tinnitus and APD affects to several parts of the ascending auditory pathway from the periphery to the auditory cortex, there could be some interrelationship between them. For instance, tinnitus has been reported to degrade the auditory localization capacity. Tinnitus is believed to be triggered by deafferentation of normal peripheral input to the central auditory system. This peripheral deficit can be accompanied by HL or not, since a type of permanent cochlear damage (thus deafferentation) without an elevation of hearing thresholds might persist. Therefore, a combined study of APD, tinnitus and HL on the same cohort of patients can be audiologically relevant and worthy. Methods: Statistical analysis is applied to a cohort of 305 patients attending an audiology clinic in Madrid (Spain). This group of patients is first categorized in four subgroups, namely, HLTG (with tinnitus and HL), NHLTG (with tinnitus and without HL), HLNTG (with HL but no tinnitus), and NHLNTG (neither tinnitus nor HL). The statistical variables include Age, Average Auditory Threshold (ATT), for assessing HL, Tinnitus Handicap Inventory (THI), for measuring tinnitus, and a new 25-item Auditory Behavior Questionnaire (ABQ), for scoring APD. Factor analysis is applied to arrange these items into 4 subscales. The internal consistency reliability of this ABQ is confirmed by calculating Cronbach's coefficients α. The test-retest reliability is assessed by the intraclass correlation coefficients, ICC. Statistical techniques applied to the data set include descriptive analysis of variables and Spearman rank correlations (ρ) between them. Results: Overall reliability of ABQ is confirmed by an α value of 0.89 and by an ICC of 0.91. Regarding the internal consistency reliability, the four subscales prove a fairly good consistency with α coefficients above 0.7. Average values of statistical variables show significantly lower age of patients with tinnitus and no HL, which can provide a cue of noise overexposure of this segment of population. These younger patients show also decreased ABQ and similar THI in comparison with patients in the other subgroups. A strong correlation (ρ = 0.63) was found between AAT and Age for the HLNTG subgroup. For the HLTG subgroup, a moderate correlation (ρ = 0.44) was found between ABQ and THI. Conclusion: The utilized questionnaire (ABQ), together with AAT and THI, can help to study comorbid hearing impairments in patients regularly attending an audiological clinic.

Tinnitus with a normal audiogram: Relation to noise exposure but no evidence for cochlear synaptopathy

In rodents, exposure to high-level noise can destroy synapses between inner hair cells and auditory nerve fibers, without causing hair cell loss or permanent threshold elevation. Such "cochlear synaptopathy" is associated with amplitude reductions in wave I of the auditory brainstem response (ABR) at moderate-to-high sound levels. Similar ABR results have been reported in humans with tinnitus and normal audiometric thresholds, leading to the suggestion that tinnitus in these cases might be a consequence of synaptopathy. However, the ABR is an indirect measure of synaptopathy and it is unclear whether the results in humans reflect the same mechanisms demonstrated in rodents. Measures of noise exposure were not obtained in the human studies, and high frequency audiometric loss may have impacted ABR amplitudes. To clarify the role of cochlear synaptopathy in tinnitus with a normal audiogram, we recorded ABRs, envelope following responses (EFRs), and noise exposure histories in young adults with tinnitus and matched controls. Tinnitus was associated with significantly greater lifetime noise exposure, despite close matching for age, sex, and audiometric thresholds up to 14 kHz. However, tinnitus was not associated with reduced ABR wave I amplitude, nor with significant effects on EFR measures of synaptopathy. These electrophysiological measures were also uncorrelated with lifetime noise exposure, providing no evidence of noise-induced synaptopathy in this cohort, despite a wide range of exposures. In young adults with normal audiograms, tinnitus may be related not to cochlear synaptopathy but to other effects of noise exposure.

Non-Monotonic Relation between Noise Exposure Severity and Neuronal Hyperactivity in the Auditory Midbrain

The occurrence of tinnitus can be linked to hearing loss in the majority of cases, but there is nevertheless a large degree of unexplained heterogeneity in the relation between hearing loss and tinnitus. Part of the problem might be that hearing loss is usually quantified in terms of increased hearing thresholds, which only provides limited information about the underlying cochlear damage. Moreover, noise exposure that does not cause hearing threshold loss can still lead to “hidden hearing loss” (HHL), i.e., functional deafferentation of auditory nerve fibers (ANFs) through loss of synaptic ribbons in inner hair cells. While it is known that increased hearing thresholds can trigger increases in spontaneous neural activity in the central auditory system, i.e., a putative neural correlate of tinnitus, the central effects of HHL have not yet been investigated. Here, we exposed mice to octave-band noise at 100 and 105 dB SPL to generate HHL and permanent increases of hearing thresholds, respectively. Deafferentation of ANFs was confirmed through measurement of auditory brainstem responses and cochlear immunohistochemistry. Acute extracellular recordings from the auditory midbrain (inferior colliculus) demonstrated increases in spontaneous neuronal activity (a putative neural correlate of tinnitus) in both groups. Surprisingly, the increase in spontaneous activity was most pronounced in the mice with HHL, suggesting that the relation between hearing loss and neuronal hyperactivity might be more complex than currently understood. Our computational model indicated that these differences in neuronal hyperactivity could arise from different degrees of deafferentation of low-threshold ANFs in the two exposure groups. Our results demonstrate that HHL is sufficient to induce changes in central auditory processing, and they also indicate a non-monotonic relationship between cochlear damage and neuronal hyperactivity, suggesting an explanation for why tinnitus might occur without obvious hearing loss and conversely why hearing loss does not always lead to tinnitus.

Audiometric characteristics of hyperacusis patients

Hyperacusis is a frequent auditory disorder where sounds of normal volume are perceived as too loud or even painfully loud. There is a high degree of co-morbidity between hyperacusis and tinnitus, most hyperacusis patients also have tinnitus, but only about 30–40% of tinnitus patients also show symptoms of hyperacusis. In order to elucidate the mechanisms of hyperacusis, detailed measurements of loudness discomfort levels (LDLs) across the hearing range would be desirable. However, previous studies have only reported LDLs for a restricted frequency range, e.g., from 0.5 to 4 kHz or from 1 to 8 kHz. We have measured audiograms and LDLs in 381 patients with a primary complaint of hyperacusis for the full standard audiometric frequency range from 0.125 to 8 kHz. On average, patients had mild high-frequency hearing loss, but more than a third of the tested ears had normal hearing thresholds (HTs), i.e., ≤20 dB HL. LDLs were found to be significantly decreased compared to a normal-hearing reference group, with average values around 85 dB HL across the frequency range. However, receiver operating characteristic analysis showed that LDL measurements are neither sensitive nor specific enough to serve as a single test for hyperacusis. There was a moderate positive correlation between HTs and LDLs (r = 0.36), i.e., LDLs tended to be higher at frequencies where hearing loss was present, suggesting that hyperacusis is unlikely to be caused by HT increase, in contrast to tinnitus for which hearing loss is a main trigger. Moreover, our finding that LDLs are decreased across the full range of audiometric frequencies, regardless of the pattern or degree of hearing loss, indicates that hyperacusis might be due to a generalized increase in auditory gain. Tinnitus on the other hand is thought to be caused by neuroplastic changes in a restricted frequency range, suggesting that tinnitus and hyperacusis might not share a common mechanism.

Tinnitus prevalence in the city of São Paulo

Introduction

The public and private health care in the city of São Paulo has no data on tinnitus prevalence.

Objective

Determine tinnitus prevalence in São Paulo city.

Study design

Series study.

Methods

Cross-sectional study by field questionnaire with 1960 interviews. Predictor variables included gender, age, tinnitus.

Results

The prevalence of tinnitus was 22%. It affects more women (26%) than men (17%) and increases with advancing age. Approximately one third of cases (32%) assert that they have constant tinnitus (i.e., “ringing”), while most describe intermittent tinnitus (68%). The majority (64%) reported feeling annoyed, while others (36%) denied any annoyance. Among women, the occurrence of an annoying tinnitus was significantly higher (73%) than among men (50%). The percentages were: mildly annoying (11%), moderately annoying (55%), and severely annoying (34%). Tinnitus interferes with daily activities in 18% of those reporting to be annoyed.

Conclusion

The population in the city of São Paulo suffering from tinnitus was more prevalent than previously estimated. Generally, it affects more women and those without occupation, and increases significantly with age. Most respondents described the tinnitus as annoying, and this was more prevalent in females. The degree of discomfort measured by a Visual Analogue Scale showed moderate tinnitus, with responses averaging 6.3.

Auditory function in normal-hearing, noise-exposed human ears

OBJECTIVES

To determine whether suprathreshold measures of auditory function, such as distortion-product otoacoustic emissions (DPOAEs) and auditory brainstem responses (ABRs), are correlated with noise exposure history in normal-hearing human ears. Recent data from animal studies have revealed significant deafferentation of auditory nerve fibers after full recovery from temporary noise-induced hearing loss. Furthermore, these data report smaller ABR wave I amplitudes in noise-exposed animal ears when compared with non-noise-exposed control animals or prenoise exposure amplitudes in the same animal. It is unknown whether a similar phenomenon exists in the normal-hearing, noise-exposed human ear.

DESIGN

Thirty normal-hearing human subjects with a range of noise exposure backgrounds (NEBs) participated in this study. NEB was quantified by the use of a noise exposure questionnaire that extensively queried loud sound exposure during the previous 12 months. DPOAEs were collected at three f2s (1, 2, and 4 kHz) over a range of L2s. DPOAE stimulus level began at 80 dB forward-pressure level and decreased in 10 dB steps. Two-channel ABRs were collected in response to click stimuli and 4 kHz tone bursts; one channel used an ipsilateral mastoid electrode and the other an ipsilateral tympanic membrane electrode. ABR stimulus level began at 90 dB nHL and was decreased in 10 dB steps. Amplitudes of waves I and V of the ABR were analyzed.

RESULTS

A statistically significant relationship between ABR wave I amplitude and NEB was found for clicked-evoked ABRs recorded at a stimulus level of 90 dB nHL using a mastoid recording electrode. For this condition, ABR wave I amplitudes decreased as a function of NEB. Similar systematic trends were present for ABRs collected in response to clicks and 4 kHz tone bursts at additional suprathreshold stimulation levels (≥70 dB nHL). The relationship weakened and disappeared with decreases in stimulation level (≤60 dB nHL). Similar patterns were present for ABRs collected using a tympanic membrane electrode. However, these relationships were not statistically significant and were weaker and more variable than those collected using a mastoid electrode. In contrast to the findings for ABR wave I, wave V amplitude was not significantly related to NEB. Furthermore, there was no evidence of a systematic relationship between suprathreshold DPOAEs and NEB.

CONCLUSIONS

A systematic trend of smaller ABR wave I amplitudes was found in normal-hearing human ears with greater amounts of voluntary NEB in response to suprathreshold clicks and 4 kHz tone bursts. These findings are consistent with the data from previous work completed in animals, where the reduction in suprathreshold responses was a result of deafferentation of high-threshold/low-spontaneous rate auditory nerve fibers. These data suggest that a similar mechanism might be operating in human ears after exposure to high sound levels. However, evidence of this damage is only apparent when examining suprathreshold wave I amplitude of the ABR. In contrast, suprathreshold DPOAE level was not significantly related to NEB. This was expected, given noise-induced auditory damage findings in animal ears did not extend to the outer hair cells, the generator for the DPOAE response.

Tinnitus in men, mice (as well as other rodents), and machines

The phantom auditory sensation of tinnitus is now studied in humans, animals, and computer models, and our understanding of how tinnitus is triggered and which neural mechanisms give rise to the phantom sensation in the brain has increased considerably. In most cases, tinnitus is associated with hearing loss, and even tinnitus patients with normal hearing thresholds might have cochlear damage that is not detected through conventional audiometry, as has been recently shown through auditory brainstem response measurements. Animals show behavioural signs of tinnitus after induction of hearing loss, indicating a causal relation. Moreover, surgical reduction of hearing loss in otosclerosis can reduce or even abolish tinnitus. However, hearing loss does not always lead to tinnitus. Psychophysical measurements have indicated that certain types of cochlear damage might be more closely linked to tinnitus than others. Recent animal studies have used behavioural testing to distinguish between animals with and without tinnitus after noise exposure. Comparisons between these groups of animals have helped identify neural correlates of tinnitus as well as factors that could represent a predisposition for tinnitus. Human neuroimaging studies have also begun to separate the neural signature of tinnitus from other consequences of hearing loss. The functional mechanisms that could underlie tinnitus development tinnitus have been analysed in computational modelling studies, which indicate that tinnitus could be a side-effect of the brain's attempt to compensate for hearing loss. Even though causal treatments for tinnitus are currently not available, hearing aids can provide considerable benefit when used in conjunction with counselling, tinnitus retraining therapy or cognitive behavioural therapy. Finally, animal studies demonstrate that the development of chronic noise-induced tinnitus might be prevented through timely interventions after noise exposure. This article is part of a Special Issue entitled <Annual Reviews 2014>.

Assessment of tonotopically organised subdivisions in human auditory cortex using volumetric and surface-based cortical alignments

Although orderly representations of sound frequency in the brain play a guiding role in the investigation of auditory processing, a rigorous statistical evaluation of cortical tonotopic maps has so far hardly been attempted. In this report, the group‐level significance of local tonotopic gradients was assessed using mass‐multivariate statistics. The existence of multiple fields on the superior surface of the temporal lobe in both hemispheres was shown. These fields were distinguishable on the basis of tonotopic gradient direction and may likely be identified with the human homologues of the core areas AI and R in primates. Moreover, an objective comparison was made between the usage of volumetric and surface‐based registration methods. Although the surface‐based method resulted in a better registration across subjects of the grey matter segment as a whole, the alignment of functional subdivisions within the cortical sheet did not appear to improve over volumetric methods. This suggests that the variable relationship between the structural and the functional characteristics of auditory cortex is a limiting factor that cannot be overcome by morphology‐based registration techniques alone. Finally, to illustrate how the proposed approach may be used in clinical practice, the method was used to test for focal differences regarding the tonotopic arrangements in healthy controls and tinnitus patients. No significant differences were observed, suggesting that tinnitus does not necessarily require tonotopic reorganisation to occur. Hum Brain Mapp 35:1544–1561, 2014. © 2013 Wiley Periodicals, Inc.

Efficacy of myofascial trigger point deactivation for tinnitus control

Chronic pain in areas surrounding the ear may influence tinnitus.

Objective

To investigate the efficacy of myofascial trigger point deactivation for the relief of tinnitus.

Method

A double-blind randomized clinical trial enrolled 71 patients with tinnitus and myofascial pain syndrome. The experimental group (n = 37) underwent 10 sessions of myofascial trigger point deactivation and the control group (n = 34), 10 sessions with sham deactivation.

Results

Treatment of the experimental group was effective for tinnitus relief (p < 0.001). Pain and tinnitus relieves were associated (p = 0.013), so were the ear with worst tinnitus and the side of the body with more pain (p < 0.001). The presence of temporary tinnitus modulation (increase or decrease) upon initial muscle palpation was frequent in both groups, but its temporary decrease was related to the persistent relief at the end of treatment (p = 0.002).

Conclusion

Besides medical and audiological investigation, patients with tinnitus should also be checked for: 1) presence of myofascial pain surrounding the ear; 2) laterality between both symptoms; 3) initial decrease of tinnitus during muscle palpation. Treating this specific subgroup of tinnitus patients with myofascial trigger point release may provide better results than others described so far.