A biochemical model of peripheral tinnitus

A peripherally acting μ-opioid receptor antagonist for treating opioid-associated tinnitus: A case report

BACKGROUND

The use of opioids occasionally causes tinnitus. However, there is a paucity of data regarding the use of peripherally acting μ-opioid receptor antagonists for opioid-associated tinnitus in patients with cancer.

ACTUAL CASE

A 74-year-old male with pancreatic cancer complained of abdominal pain. Two days after initiating oxycodone therapy, the patient experienced tinnitus during body movements. Although peripheral tinnitus disappeared after discontinuing oxycodone, it reappeared with hydromorphone or tapentadol administration.

POSSIBLE COURSES OF ACTION

Drug cessation is a preferred intervention for drug-induced tinnitus; however, the cessation of opioids may not be feasible in patients with cancer who are already taking opioids.

FORMULATION OF A PLAN

Based on the presumed mechanism of peripheral tinnitus, the use of peripherally acting μ-opioid receptor antagonists was planned, and 200 μg/day of naldemedine was prescribed for tinnitus relief.

OUTCOME

Tinnitus disappeared immediately after initiating naldemedine, and the pain was well-controlled. The effect was preserved after increasing or switching opioids.

LESSONS

The use of peripherally acting μ-opioid receptor antagonists may be an option to treat opioid-associated tinnitus without compromising the analgesic effects.

VIEW

Further clinical data regarding the secondary effect of peripherally acting μ-opioid receptor antagonists on opioid-associated complications other than constipation are required.

A genome-wide association study of tinnitus reveals shared genetic links to neuropsychiatric disorders

Tinnitus, a phantom perception of sound in the absence of any external sound source, is a prevalent health condition often accompanied by psychiatric comorbidities. Recent genome-wide association studies (GWAS) highlighted a polygenic nature of tinnitus susceptibility. A shared genetic component between tinnitus and psychiatric conditions remains elusive. Here we present a GWAS using the UK Biobank to investigate the genetic processes linked to tinnitus and tinnitus-related distress, followed by gene-set enrichment analyses. The UK Biobank sample comprised 132,438 individuals with tinnitus and genotype data. Among the study sample, 38,525 individuals reported tinnitus, and 26,889 participants mentioned they experienced tinnitus-related distress in daily living. The genome-wide association analyses were conducted on tinnitus and tinnitus-related distress. We conducted enrichment analyses using FUMA to further understand the genetic processes linked to tinnitus and tinnitus-related distress. A genome-wide significant locus (lead SNP: rs71595470) for tinnitus was obtained in the vicinity of GPM6A. Nineteen independent loci reached suggestive association with tinnitus. Fifteen independent loci reached suggestive association with tinnitus-related distress. The enrichment analysis revealed a shared genetic component between tinnitus and psychiatric traits, such as bipolar disorder, feeling worried, cognitive ability, fast beta electroencephalogram, and sensation seeking. Metabolic, cardiovascular, hematological, and pharmacological gene sets revealed a significant association with tinnitus. Anxiety and stress-related gene sets revealed a significant association with tinnitus-related distress. The GWAS signals for tinnitus were enriched in the hippocampus and cortex, and for tinnitus-related distress were enriched in the brain and spinal cord. This study provides novel insights into genetic processes associated with tinnitus and tinnitus-related distress and demonstrates a shared genetic component underlying tinnitus and psychiatric conditions. Further collaborative attempts are necessary to identify genetic components underlying the phenotypic heterogeneity in tinnitus and provide biological insight into the etiology.

Ginkgo biloba for tinnitus

BACKGROUND

Tinnitus is a symptom defined as the perception of sound in the absence of an external source. In England alone there are an estimated ¾ million general practice consultations every year where the primary complaint is tinnitus, equating to a major burden on healthcare services. Clinical management strategies include education and advice, relaxation therapy, tinnitus retraining therapy (TRT), cognitive behavioural therapy (CBT), sound enrichment using ear-level sound generators or hearing aids, and drug therapies to manage co-morbid symptoms such as insomnia, anxiety or depression.  OBJECTIVES: To assess the effects of Ginkgo biloba for tinnitus in adults and children.

SEARCH METHODS

The Cochrane ENT Information Specialist searched the Cochrane ENT Register; CENTRAL (2022, Issue 6); Ovid MEDLINE; Ovid Embase; CINAHL; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished trials. The date of the search was 7 June 2022.

SELECTION CRITERIA

Randomised controlled trials (RCTs) recruiting adults and children with acute or chronic subjective tinnitus. We included studies where the intervention involved Ginkgo biloba and this was compared to placebo, no intervention, or education and information. Concurrent use of other medication or other treatment was acceptable if used equally in each group. Where an additional intervention was used equally in both groups, we analysed this as a separate comparison. The review included all courses of Ginkgo biloba, regardless of dose regimens or formulations, and for any duration of treatment.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were tinnitus symptom severity measured as a global score on a multi-item tinnitus questionnaire and serious adverse effects (bleeding, seizures). Our secondary outcomes were tinnitus loudness (change in subjective perception), tinnitus intrusiveness, generalised depression, generalised anxiety, health-related quality of life and other adverse effects (gastrointestinal upset, headache, allergic reaction). We used GRADE to assess the certainty of the evidence for each outcome.

MAIN RESULTS

This review included 12 studies (with a total of  1915 participants). Eleven studies compared the effects of Ginkgo biloba with placebo and one study compared the effects of Ginkgo biloba with hearing aids to hearing aids alone. All included studies were parallel-group RCTs. In general, risk of bias was high or unclear due to selection bias and poor reporting of allocation concealment and blinding of participants, personnel and outcome assessments. Due to heterogeneity in the outcomes measured and measurement methods used, only limited data pooling was possible.  Ginkgo biloba versus placebo When we pooled data from two studies for the primary outcome tinnitus symptom severity, we found that Ginkgo biloba may have little to no effect (Tinnitus Handicap Inventory scores) at three to six months compared to placebo, but the evidence is very uncertain (mean difference (MD) -1.35 (scale 0 to 100), 95% confidence interval (CI) -8.26 to 5.55; 2 studies; 85 participants) (very low-certainty). Ginkgo biloba may result in little to no difference in the risk of bleeding or seizures, with no serious adverse effects reported in either group (4 studies; 1154 participants; low-certainty). For the secondary outcomes, one study found that there may be little to no difference between the effects of Ginkgo biloba and placebo on tinnitus loudness measured with audiometric loudness matching at 12 weeks, but the evidence is very uncertain (MD -4.00 (scale -10 to 140 dB), 95% CI -13.33 to 5.33; 1 study; 73 participants) (very low-certainty). One study found that there may be little to no difference between the effects of Ginkgo biloba and placebo on health-related quality of life measured with the Glasgow Health Status Inventory at three months (MD -0.58 (scale 0 to 100), 95% CI -4.67 to 3.51; 1 study; 60 participants) (low-certainty). Ginkgo biloba may not increase the frequency of other adverse effects (gastrointestinal upset, headache, allergic reaction) at three months compared to placebo (risk ratio 0.91, 95% CI 0.52 to 1.60; 4 studies; 1175 participants) (low-certainty). None of the studies reported the other secondary outcomes of tinnitus intrusiveness or changes in depressive symptoms or depression, anxiety symptoms or generalised anxiety. Gingko biloba with concurrent intervention versus concurrent intervention only One study compared Ginkgo biloba with hearing aids to hearing aids only. It assessed the mean difference in the change in Tinnitus Handicap Inventory scores and tinnitus loudness using a 10-point visual analogue scale (VAS) at three months. The study did not report adverse effects, tinnitus intrusiveness, changes in depressive symptoms or depression, anxiety symptoms or generalised anxiety, or health-related quality of life. This was a single, very small study (22 participants) and for all outcomes the certainty of the evidence was very low. We were unable to draw meaningful conclusions from the numerical results.

AUTHORS' CONCLUSIONS

There is uncertainty about the benefits and harms of Ginkgo biloba for the treatment of tinnitus when compared to placebo. We were unable to draw meaningful conclusions regarding the benefits and harms of Ginkgo biloba when used with concurrent intervention (hearing aids). The certainty of the evidence for the reported outcomes, assessed using GRADE, ranged from low to very low. Future research into the effectiveness of Ginkgo biloba in patients with tinnitus should use rigorous methodology. Randomisation and blinding should be of the highest quality, given the subjective nature of tinnitus and the strong likelihood of a placebo response. The CONSORT statement should be used in the design and reporting of future studies. We also recommend the use of validated, patient-centred outcome measures for research in the field of tinnitus.

Electrical signaling in cochlear efferents is driven by an intrinsic neuronal oscillator

Efferent neurons are believed to play essential roles in maintaining auditory function. The lateral olivocochlear (LOC) neurons-which project from the brainstem to the inner ear, where they release multiple transmitters including peptides, catecholamines, and acetylcholine-are the most numerous yet least understood elements of efferent control of the cochlea. Using in vitro calcium imaging and patch-clamp recordings, we found that LOC neurons in juvenile and young adult mice exhibited extremely slow waves of activity (∼0.1 Hz). These seconds-long bursts of Na⁺ spikes were driven by an intrinsic oscillator dependent on L-type Ca²⁺ channels and were not observed in prehearing mice, suggesting an age-dependent mechanism underlying the intrinsic oscillator. Using optogenetic approaches, we identified both ascending (T-stellate cells of the cochlear nucleus) and descending (auditory cortex) sources of synaptic excitation, as well as the synaptic receptors used for such excitation. Additionally, we identified potent inhibition originating in the glycinergic medial nucleus of trapezoid body (MNTB). Conductance-clamp experiments revealed an unusual mechanism of electrical signaling in LOC neurons, in which synaptic excitation and inhibition served to switch on and off the intrinsically generated spike burst mechanism, allowing for prolonged periods of activity or silence controlled by brief synaptic events. Protracted bursts of action potentials may be essential for effective exocytosis of the diverse transmitters released by LOC fibers in the cochlea.

Measurement of Loudness Discomfort Levels as a Test for Hyperacusis: Test-Retest Reliability and Its Clinical Value

Objectives

The aims of this study were to investigate the test-retest reliability of measurements of loudness discomfort levels (LDLs), to suggest cut-off values for diagnosing patients with hyperacusis, and to evaluate the clinical value of-LDL measurements as a test for monitoring hyperacusis.

Methods

For the test-retest reliability of LDL measurements (study 1), a total of 68 patients who sought consultations at our clinic were subcategorized into four groups: patients with tinnitus (group 1), tinnitus and hearing loss (group 2), hyperacusis (group 3), and normal controls (group 4). Inter-hour and inter-day test-retest reliability values using different stimuli were investigated. For study 2, the clinical value of LDL measurements using pure tone stimuli was analyzed by comparing changes after sound generator use in patients with hyperacusis.

Results

In study 1, the group 3 patients showed significantly lower LDLs than the other groups. High test-retest reliability of LDL tests was demonstrated, regardless of the type of stimulus used. The cut-off values for screening patients with hyperacusis were 90 dB HL using pure tone stimuli and 62 dB HL using white-band noise stimuli. In study 2, significantly increased LDLs were correlated with improved symptoms and improved scores on tinnitus questionnaires after sound generator use, indicating that LDL measurement is a reliable test for monitoring hyperacusis during an intervention.

Conclusion

LDL measurement is a reliable diagnostic tool to reflect the condition of hyperacusis, especially during the course of treatment.

Evaluation of Tp-e interval, Tp-e/QT ratio and index of cardiac-electrophysiological balance in patients with tinnitus

Background

Tinnitus is a common auditory symptom. Dysfunction in the autonomic nervous system (ANS) is an essential part of the etiopathogenesis of tinnitus. ANS regulates heart rate and heart rhythm and can lead to ventricular repolarization changes, which can cause malignant ventricular arrhythmias. T wave peak-to-end T(p-e) interval and T(p-e)/QT ratio are known ventricular arrhythmia indexes, and the index of cardiac-electrophysiological balance (iCEB) is a novel index that can be used to predict the risk of malignant ventricular arrhythmia. The goal of the study was to investigate these ventricular arrhythmia indexes in patients with tinnitus.

Methods

The study population consisted of 240 patients with tinnitus and 240 healthy subjects. A standard 12-channel surface electrocardiogram was applied to both groups. T(p-e) interval, QT interval and QRS duration were determined. Corrected QT (QTc) was determined via Bazett’s formula. To predict ventricular arrhythmia, iCEB (QT/QRS), T(p-e)/QT, corrected iCEB (QTc/QRS) and T(p-e)/QTc values were determined and compared between groups.

Results

Compared to the control group, QT (376.46 ± 36.54 vs 346.52 ± 24.51 ms), QTc (426.68 ± 24.68 vs 390.42 ± 24.04 ms), T(p-e) (75.86 ± 14.68 vs 62.42 ± 8.64 ms), T(p-e)/QT (0.201 ± 0.06 vs 0.180 ± 0.01) and T(p-e)/QTc (0.177 ± 0.06 vs 0.159 ± 0.02) were significantly higher in patients with tinnitus (p < 0.001 for all). QT/QRS (3.92 ± 0.68 vs 3.56 ± 0.32) and QTc/QRS (4.44 ± 1.03 vs 4.01 ± 0.64) were also significantly higher in patients with tinnitus (p = 0.018 and p = 0.008, respectively). In addition, significant positive correlations were found between T(p-e), T(p-e)/QTc ratio and disease duration (r = 0.792, p < 0.001; r = 0.500, p < 0.001, respectively).

Conclusion

As a result, patients with tinnitus may have an increased risk of malignant ventricular arrhythmia.

Objective and Measurable Biomarkers in Chronic Subjective Tinnitus

Tinnitus is associated with increased social costs and reduced quality of life through sleep disorders or psychological distress. The pathophysiology of chronic subjective tinnitus, which accounts for most tinnitus, has not been clearly elucidated. This is because chronic subjective tinnitus is difficult to evaluate objectively, and there are no objective markers that represent the diagnosis or therapeutic effect of tinnitus. Based on the results of studies on patients with chronic subjective tinnitus, objective and measurable biomarkers that help to identify the pathophysiology of tinnitus have been summarized. A total of 271 studies in PubMed, 303 in EMBASE, and 45 in Cochrane Library were found on biomarkers related to chronic subjective tinnitus published until April 2021. Duplicate articles, articles not written in English, review articles, case reports, and articles that did not match our topic were excluded. A total of 49 studies were included. Three specimens, including blood, saliva, and urine, and a total of 58 biomarkers were used as indicators for diagnosis, evaluation, prognosis, and therapeutic effectiveness of tinnitus. Biomarkers were classified into eight categories comprising metabolic, hemostatic, inflammatory, endocrine, immunological, neurologic, and oxidative parameters. Biomarkers can help in the diagnosis, measure the severity, predict prognosis, and treatment outcome of tinnitus.

Tinnitus and tinnitus disorder: Theoretical and operational definitions (an international multidisciplinary proposal)

As for hypertension, chronic pain, epilepsy and other disorders with particular symptoms, a commonly accepted and unambiguous definition provides a common ground for researchers and clinicians to study and treat the problem. The WHO's ICD11 definition only mentions tinnitus as a nonspecific symptom of a hearing disorder, but not as a clinical entity in its own right, and the American Psychiatric Association's DSM-V doesn't mention tinnitus at all. Here we propose that the tinnitus without and with associated suffering should be differentiated by distinct terms: "Tinnitus" for the former and "Tinnitus Disorder" for the latter. The proposed definition then becomes "Tinnitus is the conscious awareness of a tonal or composite noise for which there is no identifiable corresponding external acoustic source, which becomes Tinnitus Disorder "when associated with emotional distress, cognitive dysfunction, and/or autonomic arousal, leading to behavioural changes and functional disability.". In other words "Tinnitus" describes the auditory or sensory component, whereas "Tinnitus Disorder" reflects the auditory component and the associated suffering. Whereas acute tinnitus may be a symptom secondary to a trauma or disease, chronic tinnitus may be considered a primary disorder in its own right. If adopted, this will advance the recognition of tinnitus disorder as a primary health condition in its own right. The capacity to measure the incidence, prevalence, and impact will help in identification of human, financial, and educational needs required to address acute tinnitus as a symptom but chronic tinnitus as a disorder.

Neurobiology of Stress-Induced Tinnitus

Emotional stress has accompanied humans since the dawn of time and has played an essential role not only in positive selection and adaptation to an ever-changing environment, but also in the acceleration or even initiation of many illnesses. The three main somatic mechanisms induced by stress are the hypothalamus-pituitary-adrenal axis (HPA axis), the sympathetic-adreno-medullar (SAM) axis, and the immune axis. In this chapter, the stress-induced mechanisms that can affect cochlear physiology are presented and discussed in the context of tinnitus generation and auditory neurobiology. It is concluded that all of the presented mechanisms need to be further investigated. It is advised that clinical practitioners ask patients about stressful events or chronic stress preceding the tinnitus onset and measure the vital signs. Finally, taking into account that tinnitus itself acts as a stressor, the implementation of anti-stress therapies for tinnitus treatment is recommended.

Enhanced Central Neural Gain Compensates Acoustic Trauma-induced Cochlear Impairment, but Unlikely Correlates with Tinnitus and Hyperacusis

For successful future therapeutic strategies for tinnitus and hyperacusis, a subcategorization of both conditions on the basis of differentiated neural correlates would be of invaluable advantage. In the present study, we used our refined operant conditioning animal model to divide equally noise-exposed rats into groups with either tinnitus or hyperacusis, with neither condition, or with both conditions co-occurring simultaneously. Using click stimulus and noise burst-evoked Auditory Brainstem Responses (ABR) and Distortion Product Otoacoustic Emissions, no hearing threshold difference was observed between any of the groups. However, animals with neither tinnitus nor hyperacusis responded to noise trauma with shortened ABR wave I and IV latencies and elevated central neuronal gain (increased ABR wave IV/I amplitude ratio), which was previously assumed in most of the literature to be a neural correlate for tinnitus. In contrast, animals with tinnitus had reduced neural response gain and delayed ABR wave I and IV latencies, while animals with hyperacusis showed none of these changes. Preliminary studies, aimed at establishing comparable non-invasive objective tools for identifying tinnitus in humans and animals, confirmed reduced central gain and delayed response latency in human and animals. Moreover, the first ever resting state functional Magnetic Resonance Imaging (rs-fMRI) analyses comparing humans and rats with and without tinnitus showed reduced rs-fMRI activities in the auditory cortex in both patients and animals with tinnitus. These findings encourage further efforts to establish non-invasive diagnostic tools that can be used in humans and animals alike and give hope for differentiated classification of tinnitus and hyperacusis.

Betahistine for tinnitus

BACKGROUND

Tinnitus is a symptom defined as the perception of sound in the absence of an external source. In England alone there are an estimated ¾ million general practice consultations every year where the primary complaint is tinnitus, equating to a major burden on healthcare services. Clinical management strategies include education and advice, relaxation therapy, tinnitus retraining therapy, cognitive behavioural therapy, sound enrichment using ear-level sound generators or hearing aids, and drug therapies to manage co-morbid symptoms such as sleep difficulties, anxiety or depression. As yet, no drug has been approved for tinnitus by a regulatory body. Nonetheless, over 100,000 prescriptions for betahistine are being filled every month in England, and nearly 10% of general practitioners prescribe betahistine for tinnitus.

OBJECTIVES

To assess the effects of betahistine in patients with subjective idiopathic tinnitus.

SEARCH METHODS

The Cochrane ENT Information Specialist searched the Cochrane ENT Register; Central Register of Controlled Trials (CENTRAL, via the Cochrane Register of Studies); Ovid MEDLINE; Ovid Embase; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished trials. The date of the search was 23 July 2018.

SELECTION CRITERIA

Randomised controlled trials (RCTs) recruiting patients of any age with acute or chronic subjective idiopathic tinnitus were included. We included studies where the intervention involved betahistine and this was compared to placebo, no intervention or education and information. We included all courses of betahistine, regardless of dose regimens or formulations and for any duration of treatment.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by Cochrane. Our primary outcomes included tinnitus loudness and significant adverse effects (upper gastrointestinal discomfort). Our secondary outcomes included tinnitus symptom severity as measured by the global score on a multi-item tinnitus questionnaire, depressive symptoms, symptoms of generalised anxiety, health-related quality of life, other adverse effects (e.g. headache, drowsiness, allergic skin reactions (pruritis, rashes) and exacerbation of tinnitus) and tinnitus intrusiveness. We used GRADE to assess the quality of evidence for each outcome; this is indicated in italics.

MAIN RESULTS

This review included five studies (with a total of 303 to 305 participants) comparing the effects of betahistine with placebo in adults with subjective idiopathic tinnitus. Four studies were parallel-group RCTs and one had a cross-over design. The risk of bias was unclear in all of the included studies.Due to heterogeneity in the outcomes measured and measurement methods used, very limited data pooling was possible. When we pooled the data from two studies for the primary outcome tinnitus loudness, the mean difference on a 0- to 10-point visual analogue scale at one-month follow-up was not significant between betahistine and placebo (-0.16, 95% confidence interval (CI) -1.01 to 0.70; 81 participants) (very low-quality evidence). There were no reports of upper gastrointestinal discomfort (significant adverse effect) in any study.As a secondary outcome, one study found no difference in the change in the Tinnitus Severity Index between betahistine and placebo (mean difference at 12 weeks 0.02, 95% CI -1.05 to 1.09; 50 participants) (moderate-quality evidence). None of the studies reported the other secondary outcomes of changes in depressive symptoms or depression, anxiety symptoms or generalised anxiety, or health-related quality of life as measured by a validated instrument, nor tinnitus intrusiveness.Other adverse effects that were reported were not treatment-related.

AUTHORS' CONCLUSIONS

There is an absence of evidence to suggest that betahistine has an effect on subjective idiopathic tinnitus when compared to placebo. The evidence suggests that betahistine is generally well tolerated with a similar risk of adverse effects to placebo treatments. The quality of evidence for the reported outcomes, using GRADE, ranged from moderate to very low.If future research into the effectiveness of betahistine in patients with tinnitus is felt to be warranted, it should use rigorous methodology. Randomisation and blinding should be of the highest quality, given the subjective nature of tinnitus and the strong likelihood of a placebo response. The CONSORT statement should be used in the design and reporting of future studies. We also recommend the development of validated, patient-centred outcome measures for research in the field of tinnitus.

Sound therapy (using amplification devices and/or sound generators) for tinnitus

BACKGROUND

Tinnitus affects 10% to 15% of the adult population, with about 20% of these experiencing symptoms that negatively affect quality of life. In England alone there are an estimated ¾ million general practice consultations every year where the primary complaint is tinnitus, equating to a major burden on healthcare services. Clinical management strategies include education and advice, relaxation therapy, tinnitus retraining therapy (TRT), cognitive behavioural therapy (CBT), sound enrichment using ear-level sound generators or hearing aids, and drug therapies to manage co-morbid symptoms such as insomnia, anxiety or depression. Hearing aids, sound generators and combination devices (amplification and sound generation within one device) are a component of many tinnitus management programmes and together with information and advice are a first line of management in audiology departments for someone who has tinnitus.

OBJECTIVES

To assess the effects of sound therapy (using amplification devices and/or sound generators) for tinnitus in adults.

SEARCH METHODS

The Cochrane ENT Information Specialist searched the Cochrane ENT Register; Central Register of Controlled Trials (CENTRAL, via the Cochrane Register of Studies); Ovid MEDLINE; Ovid Embase; CINAHL; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished trials. The date of the search was 23 July 2018.

SELECTION CRITERIA

Randomised controlled trials (RCTs) recruiting adults with acute or chronic subjective idiopathic tinnitus. We included studies where the intervention involved hearing aids, sound generators or combination hearing aids and compared them to waiting list control, placebo or education/information only with no device. We also included studies comparing hearing aids to sound generators, combination hearing aids to hearing aids, and combination hearing aids to sound generators.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by Cochrane. Our primary outcomes were tinnitus symptom severity as measured as a global score on multi-item tinnitus questionnaire and significant adverse effects as indicated by an increase in self-reported tinnitus loudness. Our secondary outcomes were depressive symptoms, symptoms of generalised anxiety, health-related quality of life and adverse effects associated with wearing the device such as pain, discomfort, tenderness or skin irritation, or ear infections. We used GRADE to assess the quality of evidence for each outcome; this is indicated in italics.

MAIN RESULTS

This review included eight studies (with a total of 590 participants). Seven studies investigated the effects of hearing aids, four combination hearing aids and three sound generators. Seven studies were parallel-group RCTs and one had a cross-over design. In general, risk of bias was unclear due to lack of detail about sequence generation and allocation concealment. There was also little or no use of blinding.No data for our outcomes were available for any of our three main comparisons (comparing hearing aids, sound generators and combination devices with a waiting list control group, placebo or education/information only). Data for our additional comparisons (comparing these devices with each other) were also few, with limited potential for data pooling.Hearing aid only versus sound generator device onlyOne study compared patients fitted with sound generators versus those fitted with hearing aids and found no difference between them in their effects on our primary outcome, tinnitus symptom severity measured with the Tinnitus Handicap Inventory (THI) at 3, 6 or 12 months (low-quality evidence). The use of both types of device was associated with a clinically significant reduction in tinnitus symptom severity.Combination hearing aid versus hearing aid onlyThree studies compared combination hearing aids with hearing aids and measured tinnitus symptom severity using the THI or Tinnitus Functional Index. When we pooled the data we found no difference between them (standardised mean difference -0.15, 95% confidence interval -0.52 to 0.22; three studies; 114 participants) (low-quality evidence). The use of both types of device was again associated with a clinically significant reduction in tinnitus symptom severity.Adverse effects were not assessed in any of the included studies.None of the studies measured the secondary outcomes of depressive symptoms or depression, anxiety symptoms or generalised anxiety, or health-related quality of life as measured by a validated instrument, nor the newly developed core outcomes tinnitus intrusiveness, ability to ignore, concentration, quality of sleep and sense of control.

AUTHORS' CONCLUSIONS

There is no evidence to support the superiority of sound therapy for tinnitus over waiting list control, placebo or education/information with no device. There is insufficient evidence to support the superiority or inferiority of any of the sound therapy options (hearing aid, sound generator or combination hearing aid) over each other. The quality of evidence for the reported outcomes, assessed using GRADE, was low. Using a combination device, hearing aid or sound generator might result in little or no difference in tinnitus symptom severity.Future research into the effectiveness of sound therapy in patients with tinnitus should use rigorous methodology. Randomisation and blinding should be of the highest quality, given the subjective nature of tinnitus and the strong likelihood of a placebo response. The CONSORT statement should be used in the design and reporting of future studies. We also recommend the use of validated, patient-centred outcome measures for research in the field of tinnitus.

Tinnitus: The Sound of Stress?

Background:

Emotional stress is frequently associated with otologic symptoms as tinnitus and dizziness. Stress can contribute to the beginning or worsening of tinnitus.

Objective:

The objective of the study is to evaluate the presence of stress symptoms in patients with chronic, subjective tinnitus, and correlate its presence to annoyance associated with tinnitus.

Methods:

This is a cross-sectional study. One hundred and eighty patients with chronic, subjective tinnitus were included. Patients answered the Tinnitus Handicap Inventory (THI) to evaluate the impact of tinnitus in the quality of life and answered the Lipp's inventory symptoms of stress for adults (ISSL). The data obtained was organized using Excel® 2010, mean values, linear regression and p-value were calculated.

Results:

Of the 180 patients included in the study, 117 (65%) had stress symptoms, 52 of the 117 (44%) were in the resistance phase and 23 of the 117 (20%) in the exhaustion phase, the remaining was in the alert phase. There was a clear progressive increase in stress as THI raised, with more impact of tinnitus in quality of life.

Conclusion:

The presence of stress symptoms, measured by ISSL was observed in most of our patients with chronic subjective tinnitus, specially in the resistance and exhaustion phases and it is directly associated with tinnitus annoyance.

Associations between hyperacusis and psychosocial work factors in the general population

Purpose

We investigated the association between hyperacusis and aspects of psychosocial work environment in a general population. The objectives were to investigate (1) prevalence and characteristics (among age, sex, access to social support at home, education, smoking, physical exercise, and perceived general health) of hyperacusis in a general working population and (2) associations between hyperacusis and psychosocial factors in the work environment. The psychosocial work aspects included effort, reward, overcommitment, worry, and social and emotional support.

Methods

Using data from a sample stratified for age and sex from the Österbotten Environmental Health Study in Finland, currently employed participants with self-reported hyperacusis and referents were compared on questionnaire instruments quantifying six aspects of their psychosocial work environment.

Results

Among 856 currently employed participants, 47 constituted a hyperacusis group and 809 a reference group. The hyperacusis group scored significantly higher than the referents on worry at work, social support at work, and reward at work, but not on emotional support at work, work overcommitment, or effort at work. About 40% of the hyperacusis group scored on the upper quartile of the three former work environment factors, with odds ratios ranging from 1.91 to 2.56.

Conclusions

The results suggest that worrying about aspects at work, perceiving low social support, and not perceiving being rewarded at work are associated with hyperacusis.

Increased parietal circuit-breaker activity in delta frequency band and abnormal delta/theta band connectivity in salience network in hyperacusis subjects

Recent studies have suggested that hyperacusis, an abnormal hypersensitivity to ordinary environmental sounds, may be characterized by certain resting-state cortical oscillatory patterns, even with no sound stimulus. However, previous studies are limited in that most studied subjects with other comorbidities that may have affected cortical activity. In this regard, to assess ongoing cortical oscillatory activity in idiopathic hyperacusis patients with no comorbidities, we compared differences in resting-state cortical oscillatory patterns between five idiopathic hyperacusis subjects and five normal controls. The hyperacusis group demonstrated significantly higher electrical activity in the right auditory-related cortex for the gamma frequency band and left superior parietal lobule (SPL) for the delta frequency band versus the control group. The hyperacusis group also showed significantly decreased functional connectivity between the left auditory cortex (AC) and left orbitofrontal cortex (OFC), between the left AC and left subgenual anterior cingulate cortex (sgACC) for the gamma band, and between the right insula and bilateral dorsal anterior cingulate cortex (dACC) and between the left AC and left sgACC for the theta band versus the control group. The higher electrical activity in the SPL may indicate a readiness of “circuit-breaker” activity to shift attention to forthcoming sound stimuli. Also, because of the disrupted salience network, consisting of the dACC and insula, abnormally increased salience to all sound stimuli may emerge, as a consequence of decreased top-down control of the AC by the dACC and dysfunctional emotional weight attached to auditory stimuli by the OFC. Taken together, abnormally enhanced attention and salience to forthcoming sound stimuli may render hyperacusis subjects hyperresponsive to non-noxious auditory stimuli.

Stress Reactivity in Chronic Tinnitus

Tinnitus is primarily an auditory symptom. Yet not only patients and clinicians, but also current pathophysiological models relate the onset and maintenance of tinnitus to stress. Here physiological and psychological stress reactivity was investigated in 19 patients with subjective chronic tinnitus and 19 comparable healthy controls. All participants underwent five consecutive measurements in one session including three resting conditions and two stress tasks in between (mental arithmetic and concentration on tinnitus/ear noise). Stress reactivity was assessed by heart rate (HR), heart rate variability (HRV) and subjective ratings for each of the five measurements. In patients with tinnitus, mean HR was overall decreased and blunted in response to acute stress induced by mental arithmetic compared to controls. HRV measures did not differ between both groups. Tinnitus sufferers indicated more subjective stress and increased awareness of tinnitus after the mental arithmetic task (during both resting and concentration on tinnitus measurements), but perceived similar levels of stress during mental arithmetic stress. In contrast to controls, HR and HRV were not correlated and also strain reports and physiological data were not associated in tinnitus. Our data show hints for a de-synchronization of physiological and psychological stress reactivity in chronic tinnitus.

Zinc supplementation for tinnitus

BACKGROUND

Tinnitus is the perception of sound without external acoustic stimuli. Patients with severe tinnitus may have physical and psychological complaints and their tinnitus can cause deterioration in their quality of life. At present no specific therapy for tinnitus has been found to be satisfactory in all patients. In recent decades, a number of reports have suggested that oral zinc supplementation may be effective in the management of tinnitus. Since zinc has a role in cochlear physiology and in the synapses of the auditory system, there is a plausible mechanism of action for this treatment.

OBJECTIVES

To evaluate the effectiveness and safety of oral zinc supplementation in the management of patients with tinnitus.

SEARCH METHODS

The Cochrane ENT Information Specialist searched the ENT Trials Register; Central Register of Controlled Trials (CENTRAL 2016, Issue 6); PubMed; EMBASE; CINAHL; Web of Science; ClinicalTrials.gov; ICTRP and additional sources for published and unpublished trials. The date of the search was 14 July 2016.

SELECTION CRITERIA

Randomised controlled trials comparing zinc supplementation versus placebo in adults (18 years and over) with tinnitus.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures recommended by Cochrane. Our primary outcome measures were improvement in tinnitus severity and disability, measured by a validated tinnitus-specific questionnaire, and adverse effects. Secondary outcomes were quality of life, change in socioeconomic impact associated with work, change in anxiety and depression disorders, change in psychoacoustic parameters, change in tinnitus loudness, change in overall severity of tinnitus and change in thresholds on pure tone audiometry. We used GRADE to assess the quality of the evidence for each outcome; this is indicated in italics.

MAIN RESULTS

We included three trials involving a total of 209 participants. The studies were at moderate to high risk of bias. All included studies had differences in participant selection criteria, length of follow-up and outcome measurement, precluding a meta-analysis. The participants were all adults over 18 years with subjective tinnitus, but one study conducted in 2013 (n = 109) included only elderly patients. Improvement in tinnitus severity and disabilityOnly the study in elderly patients used a validated instrument (Tinnitus Handicap Questionnaire) for this primary outcome. The authors of this cross-over study did not report the results of the two phases separately and found no significant differences in the proportion of patients reporting tinnitus improvement at four months of follow-up: 5% (5/93) versus 2% (2/94) in the zinc and placebo groups, respectively (risk ratio (RR) 2.53, 95% confidence interval (CI) 0.50 to 12.70; very low-quality evidence).None of the included studies reported any significant adverse effects. Secondary outcomesFor the secondary outcome change in tinnitus loudness, one study reported no significant difference between the zinc and placebo groups after eight weeks: mean difference in tinnitus loudness -9.71 dB (95% CI -25.53 to 6.11; very low-quality evidence). Another study also measured tinnitus loudness but used a 0- to 100-point scale. The authors of this second study reported no significant difference between the zinc and placebo groups after four months: mean difference in tinnitus loudness rating scores 0.50 (95% CI -5.08 to 6.08; very low-quality evidence).Two studies used unvalidated instruments to assess tinnitus severity. One (with 50 participants) reported the severity of tinnitus using a non-validated scale (0 to 7 points) and found no significant difference in subjective tinnitus scores between the zinc and placebo groups at the end of eight weeks of follow-up (mean difference (MD) -1.41, 95% CI -2.97 to 0.15; very low-quality evidence). A third trial (n = 50) also evaluated the improvement of tinnitus using a non-validated instrument (a 0 to 10 scale: 10 = severe and unbearable tinnitus). In this study, after eight weeks there was no difference in the proportion of patients with improvement in their tinnitus, 8.7% (2/23) treated with zinc versus 8% (2/25) of those who received a placebo (RR 1.09, 95% CI 0.17 to 7.10, very low-quality evidence).None of the included studies reported any of our other secondary outcomes (quality of life, change in socioeconomic impact associated with work, change in anxiety and depression disorders, change in psychoacoustic parameters or change in thresholds on pure tone audiometry).

AUTHORS' CONCLUSIONS

We found no evidence that the use of oral zinc supplementation improves symptoms in adults with tinnitus.

Hyperacusis Questionnaire as a Tool for Measuring Hypersensitivity to Sound in a Tinnitus Research Population

Hypersensitivity to external sounds is often comorbid with tinnitus and may be significant for adherence to certain types of tinnitus management. Therefore, a clear measure of sensitivity to sound is important. The aim of this study was to evaluate the validity and reliability of the Hyperacusis Questionnaire (HQ) for use as a measurement tool using data from a sample of 264 adults who took part in tinnitus research. We evaluated the HQ factor structure, internal consistency, convergent and discriminant validity, and floor and ceiling effects. Internal consistency was high (Cronbach's alpha = 0.88) and moderate correlations were observed between the HQ, uncomfortable loudness levels, and other health questionnaires. Confirmatory factor analysis revealed that the original HQ three-factor solution and a one-factor solution were both a poor fit to the data. Four problematic items were removed and exploratory factor analysis identified a two-factor (attentional and social) solution. The original three-factor structure of the HQ was not confirmed. All fourteen items do not accurately assess hypersensitivity to sound in a tinnitus population. We propose a 10-item (2-factor) version of the HQ, which will need to be confirmed using a new tinnitus and perhaps nontinnitus population.

Functional mapping of the auditory tract in rodent tinnitus model using manganese-enhanced magnetic resonance imaging

Animal models of salicylate-induced tinnitus have demonstrated that salicylate modulates neuronal activity in several brain structures leading to neuronal hyperactivity in auditory and non-auditory brain areas. In addition, these animal tinnitus models indicate that tinnitus can be a perceptual consequence of altered spontaneous neural activity along the auditory pathway. Peripheral and/or central effects of salicylate can account for neuronal activity changes in salicylate-induced tinnitus. Because of this ambiguity, an in vivo imaging study would be able to address the peripheral and/or central involvement of salicylate-induced tinnitus. Therefore, in the present study, we developed a novel manganese-enhanced magnetic resonance imaging (MEMRI) method to map the in vivo functional auditory tract in a salicylate-induced tinnitus animal model by administrating manganese through the round window. We found that acute salicylate-induced tinnitus resulted in higher manganese uptake in the cochlea and in the central auditory structures. Furthermore, serial MRI scans demonstrated that the manganese signal increased in an anterograde fashion from the cochlea to the cochlear nucleus. Therefore, our in vivo MEMRI data suggest that acute salicylate-induced tinnitus is associated with higher spontaneous neural activity both in peripheral and central auditory pathways.

Dynorphin release by the lateral olivocochlear efferents may inhibit auditory nerve activity: a cochlear drug delivery study

Dynorphin (dyn) is suggested to excite the auditory nerve (AN) when released by the lateral olivocochlear (LOC) efferents. However, previous studies evaluated either intravenously delivered dyn-like agents, raising the potential for systemic (central) effects, or agent concentrations unlikely to be achieved via endogenous cochlear release. This study tested the hypothesis that biologically relevant increases in dyn levels in the cochlea achieved via diffusion of the drug of (-)pentazocine across the round window membrane enhances AN firing. In general, amplitude of the cochlear whole-nerve action potential (CAP) was depressed following drug application. These results suggest that dyn released by the LOC neurons would likely act as an inhibitory transmitter substance in the LOC system; neurotransmission is one of the LOC system's vast unknowns.

Amplification with hearing aids for patients with tinnitus and co-existing hearing loss

BACKGROUND

Tinnitus is described as the perception of sound or noise in the absence of real acoustic stimulation. In the current absence of a cure for tinnitus, clinical management typically focuses on reducing the effects of co-morbid symptoms such as distress or hearing loss. Hearing loss is commonly co-morbid with tinnitus and so logic implies that amplification of external sounds by hearing aids will reduce perception of the tinnitus sound and the distress associated with it.

OBJECTIVES

To assess the effects of hearing aids specifically in terms of tinnitus benefit in patients with tinnitus and co-existing hearing loss.

SEARCH METHODS

We searched the Cochrane Ear, Nose and Throat Disorders Group Trials Register; the Cochrane Central Register of Controlled Trials (CENTRAL); PubMed; EMBASE; CINAHL; Web of Science; Cambridge Scientific Abstracts; ICTRP and additional sources for published and unpublished trials. The date of the search was 19 August 2013.

SELECTION CRITERIA

Randomised controlled trials and non-randomised controlled trials recruiting adults with subjective tinnitus and some degree of hearing loss, where the intervention involves amplification with hearing aids and this is compared to interventions involving other medical devices, other forms of standard or complementary therapy, or combinations of therapies, no intervention or placebo interventions.

DATA COLLECTION AND ANALYSIS

Three authors independently screened all selected abstracts. Two authors independently extracted data and assessed those potentially suitable studies for risk of bias. For studies meeting the inclusion criteria, we used the mean difference (MD) to compare hearing aids with other interventions and controls.

MAIN RESULTS

One randomised controlled trial (91 participants) was included in this review. We judged the trial to have a low risk of bias for method of randomisation and outcome reporting, and an unclear risk of bias for other criteria. No non-randomised controlled trials meeting our inclusion criteria were identified. The included study measured change in tinnitus severity (primary measure of interest) using a tinnitus questionnaire measure, and change in tinnitus loudness (secondary measure of interest) on a visual analogue scale. Other secondary outcome measures of interest, namely change in the psychoacoustic characteristics of tinnitus, change in self reported anxiety, depression and quality of life, and change in neurophysiological measures, were not investigated in this study. The included study compared hearing aid use to sound generator use. The estimated effect on change in tinnitus loudness or severity as measured by the Tinnitus Handicap Inventory score was compatible with benefits for both hearing aids or sound generators but no difference was found between the two alternative treatments (MD -0.90, 95% confidence interval (CI) -7.92 to 6.12) (100-point scale); moderate quality evidence. No negative or adverse events were reported.

AUTHORS' CONCLUSIONS

The current evidence base for hearing aid prescription for tinnitus is limited. To be useful, future studies should make appropriate use of blinding and be consistent in their use of outcome measures. Whilst hearing aids are sometimes prescribed as part of tinnitus management, there is currently no evidence to support or refute their use as a more routine intervention for tinnitus.

The function of BDNF in the adult auditory system

The inner ear of vertebrates is specialized to perceive sound, gravity and movements. Each of the specialized sensory organs within the cochlea (sound) and vestibular system (gravity, head movements) transmits information to specific areas of the brain. During development, brain-derived neurotrophic factor (BDNF) orchestrates the survival and outgrowth of afferent fibers connecting the vestibular organ and those regions in the cochlea that map information for low frequency sound to central auditory nuclei and higher-auditory centers. The role of BDNF in the mature inner ear is less understood. This is mainly due to the fact that constitutive BDNF mutant mice are postnatally lethal. Only in the last few years has the improved technology of performing conditional cell specific deletion of BDNF in vivo allowed the study of the function of BDNF in the mature developed organ. This review provides an overview of the current knowledge of the expression pattern and function of BDNF in the peripheral and central auditory system from just prior to the first auditory experience onwards. A special focus will be put on the differential mechanisms in which BDNF drives refinement of auditory circuitries during the onset of sensory experience and in the adult brain. This article is part of the Special Issue entitled 'BDNF Regulation of Synaptic Structure, Function, and Plasticity'.

Spontaneous reversibility of damage to outer hair cells after sodium salicylate induced ototoxicity

BACKGROUND

High sodium salicylate doses can cause reversible hearing loss and tinnitus, possibly due to reduced outer hair cell electromotility. Sodium salicylate is known to alter outer hair cell structure and function. This study determined the reversibility and cochlear recovery time after administration of an ototoxic sodium salicylate dose to guinea pigs with normal cochlear function.

STUDY DESIGN

Prospective experimental investigation.

METHODS

All animals received a single 500 mg sodium salicylate dose, but with different durations of action. Function was evaluated before drug administration and immediately before sacrifice. Cochleae were processed and viewed using scanning electron microscopy.

RESULTS

Changes in outer hair cell function were observed to be present 2 hours after drug administration, with recovery of normal anatomy beginning after 24 hours. Subsequently, derangement and distortion of cilia reduced, with effects predominantly in row three. At 168 hours, cilia were near-normal but with mild distortions which interfered with normal cochlear physiology.

CONCLUSIONS

Ciliary changes persisted for up to 168 hours after ototoxic sodium salicylate administration.

Significance of serotonin transporter gene polymorphism in tinnitus

OBJECTIVES

To assess the role of serotonin transporter gene (SLC6A4) polymorphism in tinnitus.

MATERIALS AND METHODS

Fifty-four consecutive patients experiencing subjective tinnitus and 174 healthy controls were allocated for the study. Psychoacoustic parameters of tinnitus were measured. Beck Depression Inventory was used to assess the depression level of the patients. Tinnitus Handicap Inventory was used to assess the severity of tinnitus. A visual analog scale was designed to measure the impact of tinnitus on quality of life of the patients. The 44-bp insertion-deletion in the promoter region (5-HTTLPR) and 17-bp variable number tandem repeats in the second intron of the serotonin transporter gene were assessed.

RESULTS

No difference was found between the genotypes and allele frequencies of the patients and controls regarding variable number tandem repeats and 5-HTTLPR polymorphisms (p > 0.05). There was no association between the psychoacoustic parameters of tinnitus and SLC6A4 polymorphism (p > 0.05). There was a significant association between the 5-HTTLPR polymorphism and scores from the visual analog scale of the patients (p < 0.05).

CONCLUSION

Generation of tinnitus signal is not associated with SLC6A4 polymorphism and possibly with serotonergic mechanisms. However, the "ll" genotype variant of the SLC6A4 polymorphic promoter region seems associated with the limbic and autonomic nervous system symptoms of the patients with tinnitus. Therefore, serotonergic mechanisms may help explain the neurophysiological model of tinnitus, and serotonin replacement or serotonin reuptake inhibitors may increase the success rate of tinnitus treatment modalities based on the neurophysiologic model of tinnitus.

Hearing abilities at ultra-high frequency in patients with tinnitus

OBJECTIVES

To compare tinnitus patients who have normal hearing between 250 Hz and 8 kHz with normal controls with regard to the ability of each group to hear extended high-frequency pure tone thresholds.

METHODS

We enrolled 18 tinnitus patients, each of whom had a threshold of HL <25 dB and threshold differences of <10 dB between ears at frequencies of 250 and 500 Hz and 1, 2, 4, and 8 kHz. We also enrolled age- and gender-matched normal volunteers (10 ears), for each patient. Extended high frequency pure tone audiometry was performed, and the mean hearing thresholds at 10, 12, 14, and 16 kHz of each tinnitus ear were compared with those of the 10 age- and sex-matched normal ears.

RESULTS

Of the 18 patients with tinnitus, 12 had significantly increased hearing thresholds at more than one of the four high frequencies, compared with the normal group. When we assessed results according to frequency, we found that 8 patients had decreased hearing ability at 10 kHz, 10 at 12 kHz, 8 at 14 kHz, and 4 at 16 kHz.

CONCLUSION

Some patients with tinnitus who have normal hearing below 8 kHz have decreased hearing ability at extended high-frequencies. Thus, the proportion of patients with tinnitus who have normal hearing over the entire audible range is smaller than in previous reports.

Hearing aids and tinnitus therapy: a 25-year experience

Objectives:

(1) To assess the subjective tinnitus perception of patients with audiologically proven hearing loss presenting to a tinnitus clinic, both before and after hearing aid provision; (2) to investigate subjective tinnitus perception in patients with unilateral and bilateral hearing loss; and (3) to assess the impact on tinnitus perception, if any, of a digital hearing aid programme in patients provided with hearing aids.

Design:

Prospective data collection for patients attending a tinnitus clinic over a 25-year period (1980–2004).

Setting:

University teaching hospital otolaryngology department.

Participants:

A total of 2153 consecutive patients attending a consultant-delivered specialist tinnitus clinic.

Main outcomes measures:

A visual analogue scale was used to assess the degree of tinnitus perception improvement, if any, comparing before versus after unilateral or bilateral aiding (in those with audiometrically proven hearing loss). A further assessment compared the effect of digital hearing aid programme introduction on symptomatic tinnitus perception in patients provided with unilateral or bilateral aids.

Results:

A total of 1440 patients were given hearing aids (826 unilateral and 614 bilateral). There was little difference in tinnitus perception, comparing overall aiding results in unilaterally or bilaterally aided patients. Overall, 554 (67 per cent) of unilaterally aided patients and 424 (69 per cent) of bilaterally aided patients reported some improvement in their tinnitus perception following aiding. There was a statistically significant improvement in tinnitus perception, comparing analogue aids with digital hearing aids, following introduction of a digital hearing aid programme in 2000, in both unilaterally (p < 0.001) and bilaterally (p < 0.001) aided patients.

Conclusions:

Provision of hearing aids in patients with audiometrically demonstrable hearing loss can play a very important part in tinnitus control. The additional improvement in tinnitus control observed following introduction of programmable digital aids had a summative effect in the management of these patients.

Physiological and psychological stress reactivity in chronic tinnitus

Several models of tinnitus maintenance emphasize the importance of cognitive, emotional and psychophysiological processes. These factors contribute to distress in patients with decompensated tinnitus symptoms. We investigated whether tinnitus patients show increased physiological levels of arousal, more intense stress reactivity patterns and exaggerated psychological strain compared to healthy controls. Seventy tinnitus patients and 55 healthy controls underwent various stress tests. Muscular reactivity and peripheral arousal as well as strain ratings were assessed. Tinnitus patients reported significantly more strain during stress tests compared to healthy controls. Few physiological reactivity patterns differed significantly between the two groups. The physiological data thus only partly supported a hyperreactivity hypothesis. Strain reports and physiological data were only marginally correlated. Tinnitus patients show maladaptive appraisal processes during stress exposure, yet physiological reactivity is only slightly affected. Treatment programs for patients with decompensated tinnitus symptoms should account for appraisal processes and coping mechanisms in stressful situations.

Applications of magnetic resonance spectroscopy to tinnitus research: initial data, current issues, and future perspectives

Conducting tinnitus research on humans poses challenges for investigators because of its subjective nature, the complexities involved in establishing underlying generator sites, the diversity of potential causes, and the inherent difficulties in dissociating reactive changes in the central nervous system (CNS), secondary to peripheral hearing loss, from those effects that may be due to tinnitus. One area of considerable interest concerns biomarker development, particularly in the areas of metabolism and biochemistry. Establishing a biomarker or a profile of metabolic and neurobiochemical constituents of tinnitus-related activity within the CNS could be of considerable importance for understanding the fundamental properties of this disorder. Therefore, in an effort to gain greater insight into mechanisms of tinnitus, magnetic resonance spectroscopy (MRS) is being proposed as one of the several tools that can address pertinent issues. Apart from its long-standing use in analytical chemistry and physics, MRS is also being applied with greater frequency in the neurosciences to gain insight into human brain function under normal and pathological states. By considering the history of this method and advances made to date, MRS has the potential to: (1) identify unique in vivo metabolic and neurobiochemical biomarkers associated with tinnitus in specific regions of the CNS, (2) clarify and track disease pathogenesis, (3) monitor short and long-term treatment effects, and (4) serve as a tool in testing of drugs that may be used in treatment of tinnitus.

Bi-phasic intensity-dependent opioid-mediated neural amplitude changes in the chinchilla cochlea: partial blockade by an N-Methyl-D-Aspartate (NMDA)-receptor antagonist

Dynorphins, glutamate, and glutamate-sensitive N-Methyl-D-Aspartate (NMDA) receptors exist in the mammalian cochlea. Dynorphins produce neural excitation and excitotoxic effects in the spinal cord through a kappa-opioid facilitation of NMDA receptor-sensitivity to glutamate. The kappa-opioid receptor drug agonists N-dimethylallyl-normetazocine [(-)-pentazocine (50 mmol)] and trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]-benzeneacetamide [U-50488H (100 mmol)] were administered across the cochlear round window membrane in the chinchilla. Each drug produced significant post-baseline amplitude changes in the click-evoked auditory nerve compound action potential. Amplitude changes at threshold amounted to increases in sensitivity that ranged from 4-8 decibels, measured in sound pressure level (dB SPL). The large neural amplitude increases at threshold were accompanied by progressively smaller amplitude changes at 5 and 10 dB above threshold (dB SL). However, at stimulus intensities > or =20 dB SL, post-baseline neural amplitudes were suppressed to levels below baseline and control values. These bi-phasic intensity-dependent neural amplitude changes have never before been observed following i.v. administered (-)-pentazocine in this species. Finally, the bi-phasic neural amplitude changes in U-50488H-treated (100 mmol) animals were partially blocked (except at 20 dB SL), following a round window pre-treatment with the NMDA receptor drug antagonist, dizocilpine hydrogen maleate [(+)-MK-801 (8 mmol)]. Our data suggests that endogenous dynorphins within lateral efferent olivocochlear neurons differentially modulate auditory neural excitation, possibly through cochlear NMDA receptors and glutamate. The role played by lateral efferent opioid neuromodulation at cochlear NMDA receptors, is discussed.