Maladaptive plasticity in tinnitus--triggers, mechanisms and treatment

Non-invasive therapeutic brain stimulation for treatment of resistant focal epilepsy in a teenager

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rTMS and tDCS could be more often used for treatment-resistant focal epilepsy and tinnitus.

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tDCS can be used as maintenance treatment after initial successful rTMS treatment.

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rTMS and tDCS are safe in adolescents when current safety instructions are followed.

Aims

A 13-year-old boy with symptomatic focal epilepsy due to a right parietal dysembryoplastic neuroepithelial tumor (DNET) presented pre- and post-operatively fluctuating tinnitus and sensory symptoms which became persistent after incomplete tumor resection. He received low-frequency rTMS treatment and cathodal tDCS treatment.

Methods

Case report with clinical details and pictures from rTMS and tDCS stimulation targets.

Results

The patient became symptom free with an initial low-frequency rTMS treatment series targeted to the EEG-verified epileptic zone followed by maintenance therapy at the same region with cathodal tDCS at home.

Conclusions

Both rTMS and tDCS could be more often used in adolescents when drug treatment and surgery do not cease focal epilepsy, here with fluctuating tinnitus.

Differences in Clinical Characteristics and Brain Activity between Patients with Low- and High-Frequency Tinnitus

This study was aimed at delineating and comparing differences in clinical characteristics and brain activity between patients with low- and high-frequency tinnitus (LFT and HFT, respectively) using high-density electroencephalography (EEG). This study enrolled 3217 patients with subjective tinnitus who were divided into LFT (frequency < 4000 Hz) and HFT (≥4000 Hz) groups. Data regarding medical history, Tinnitus Handicap Inventory, tinnitus matching, and hearing threshold were collected from all patients. Twenty tinnitus patients and 20 volunteers were subjected to 256-channel EEG, and neurophysiological differences were evaluated using standardized low-resolution brain electromagnetic tomography (sLORETA) source-localized EEG recordings. Significant differences in sex (p < 0.001), age (p = 0.022), laterality (p < 0.001), intensity (p < 0.001), tinnitus type (p < 0.001), persistent tinnitus (p = 0.04), average threshold (p < 0.001), and hearing loss (p = 0.028) were observed between LFT and HFT groups. The tinnitus pitch only appeared to be correlated with the threshold of the worst hearing loss in the HFT group. Compared with the controls, the LFT group exhibited increased gamma power (p < 0.05), predominantly in the posterior cingulate cortex (PCC, BA31), whereas the HFT group had significantly decreased alpha1 power (p < 0.05) in the angular gyrus (BA39) and auditory association cortex (BA22). Higher gamma linear connectivity between right BA39 and right BA41 was observed in the HFT group relative to controls (t = 3.637, p = 0.027). Significant changes associated with increased gamma in the LFT group and decreased alpha1 in the HFT group indicate that tinnitus pitch is crucial for matching between the tinnitus and control groups. Differences of band frequency energy in brain activity levels may contribute to the clinical characteristics and internal tinnitus “spectrum” differences.

Tinnitus rat model generated by laser-induced shock wave; a platform for analyzing the central nervous system after tinnitus generation

OBJECTIVE

Tinnitus is a phantom auditory sensation, which is mainly triggered by dysfunction of the peripheral auditory organ, such as cochlear disorders. Additionally, the central nervous system, specifically the limbic system, plays a crucial role in the generation and exacerbation of tinnitus. Therefore, to analyze the hypothesis that tinnitus has strong and specific association with the plastic changes in the limbic system, we assessed the neuronal plastic changes in the limbic system, including the hippocampus and the amygdala, in rats with single-sided tinnitus.

METHODS

The cochlear damage was achieved by irradiating the cochlea with laser-induced shock wave (LISW). While both hearing loss and tinnitus were confirmed after exposure of rats to LISW, the degree of tinnitus was objectively measured using gap detection behavioral tests. Following the generation of hearing loss and tinnitus, plastic changes in the neurons of the limbic system were confirmed using a molecular marker (activity regulated cytoskeleton-associated protein; Arc).

RESULTS

While the expression level of Arc-positive cells in the hippocampal CA1 showed an obvious increase in the hearing loss and tinnitus groups, a significant difference was found between the tinnitus and the control groups. In the dentate gyrus, although the largest number of Arc-positive cells was observed in the tinnitus group, there were no significant differences between the numbers of cells in the hearing loss and tinnitus groups compared to that in the control group.

CONCLUSION

Although a significant increase of Arc-positive cells in the hippocampal CA1 was observed between the tinnitus group and control, no obvious tendencies of Arc-positive cells in the limbic system were observed between the rats with and without tinnitus behavior.

Single nucleotide polymorphisms in tinnitus patients exhibiting severe distress

The association between distress caused by tinnitus and psychological factors such as depression and anxiety has been examined and reported. However, prognostic factors remain poorly understood because there are only a few reports on genetic associations. We theorized there might be an association between the grade of tinnitus distress and the genetic background related to psychological factors which might lead us to identify prognostic markers. We enrolled 138 patients who had suffered from tinnitus for over 3 months. Using Tinnitus Handicap Inventory (THI) scores, we examined the association between tinnitus distress and a genetic background related to depression or anxiety. A significant association between single nucleotide polymorphism rs131702 of the Breakpoint Cluster Region (BCR) gene and the severe THI score was identified. In addition, there was an association with the severity of the State-Trait Anxiety Inventory, an index of state anxiety severity. No association was found with the Self-Rating Depression Scale, an index of depression severity. It is reported that rs131702 of BCR in Japanese patients are related to bipolar II depression characterized by fluctuation between abnormal mood states of mania and depression. Our results indicate that rs131702 of BCR is independent of depression in this study and is, therefore, a prognostic factor unique to tinnitus. We conclude that the severity of tinnitus is associated with genes related to depression.

Association between Hyperacusis and Tinnitus

Many individuals with tinnitus report experiencing hyperacusis (enhanced sensitivity to sounds). However, estimates of the association between hyperacusis and tinnitus is lacking. Here, we investigate this relationship in a Swedish study. A total of 3645 participants (1984 with tinnitus and 1661 without tinnitus) were enrolled via LifeGene, a study from the general Swedish population, aged 18-90 years, and provided information on socio-demographic characteristics, as well as presence of hyperacusis and its severity. Tinnitus presence and severity were self-reported or assessed using the Tinnitus Handicap Inventory (THI). Phenotypes of tinnitus with (n = 1388) or without (n = 1044) hyperacusis were also compared. Of 1661 participants without tinnitus, 1098 (66.1%) were women and 563 were men (33.9%), and the mean (SD) age was 45.1 (12.9). Of 1984 participants with tinnitus, 1034 (52.1%) were women and 950 (47.9%) were men, and the mean (SD) age was 47.7 (14.0) years. Hyperacusis was associated with any tinnitus [Odds ratio (OR) 3.51, 95% confidence interval (CI) 2.99-4.13], self-reported severe tinnitus (OR 7.43, 95% CI 5.06-10.9), and THI ≥ 58 (OR 12.1, 95% CI 7.06-20.6). The association with THI ≥ 58 was greater with increasing severity of hyperacusis, the ORs being 8.15 (95% CI 4.68-14.2) for moderate and 77.4 (95% CI 35.0-171.3) for severe hyperacusis. No difference between sexes was observed in the association between hyperacusis and tinnitus. The occurrence of hyperacusis in severe tinnitus is as high as 80%, showing a very tight relationship. Discriminating the pathophysiological mechanisms between the two conditions in cases of severe tinnitus will be challenging, and optimized study designs are necessary to better understand the mechanisms behind the strong relationship between hyperacusis and tinnitus.

Nitric oxide increases gain in the ventral cochlear nucleus of guinea pigs with tinnitus

Previous work has led to the hypothesis that, during the production of noise-induced tinnitus, higher levels of nitric oxide (NO), in the ventral cochlear nucleus (VCN), increase the gain applied to a reduced input from the cochlea. To test this hypothesis, we noise-exposed 26 guinea pigs, identified evidence of tinnitus in 12 of them and then compared the effects of an iontophoretically applied NO donor or production inhibitor on VCN single unit activity. We confirmed that the mean driven firing rate for the tinnitus and control groups was the same while it had fallen in the non-tinnitus group. By contrast, the mean spontaneous rate had increased for the tinnitus group relative to the control group, while it remained the same for the non-tinnitus group. A greater proportion of units responded to exogenously applied NO in the tinnitus (56%) and non-tinnitus groups (71%) than a control population (24%). In the tinnitus group, endogenous NO facilitated the driven firing rate in 37% (7/19) of neurons and appeared to bring the mean driven rate back up to control levels by a mechanism involving N-methyl-D-aspartic acid (NMDA) receptors. By contrast, in the non-tinnitus group, endogenous NO only facilitated the driven firing rate in 5% (1/22) of neurons and there was no facilitation of driven rate in the control group. The effects of endogenous NO on spontaneous activity were unclear. These results suggest that NO is involved in increasing the gain applied to driven activity, but other factors are also involved in the increase in spontaneous activity.

Total remission or persistence of tinnitus and decreased sound level tolerance in adolescents with normal audiograms: A follow-up study

BACKGROUND

Tinnitus may reflect hidden cochlear synaptic injury that does not express in the audiogram, but leads to neuroplastic changes in auditory pathways that, in turn, reduce tolerance to sounds. Such injury may follow the exposure to loud sounds. The aim of this study was to follow-up adolescents enrolled in a private school to evaluate the prevalence of tinnitus and reduced sound level tolerance (SLT) with 1-year interval, as well as to observe rates of tinnitus persistence, remission and incidence of new cases by repeat measurements.

METHODS

In Study 1 (Sanchez et al., 2016), we evaluated 170 adolescents by a questionnaire about tinnitus and reduced tolerance to ordinary sounds and by measurements in a sound booth: audiometry (0.25-16kHz), Loudness Discomfort Levels (LDL, 0.5-4kHz) and tinnitus pitch/loudness matching (if present). Tinnitus measured in the booth was then called "confirmed tinnitus." In Study 2, we revaluated 54 adolescents who returned voluntarily 1 year later to repeat all measurements.

RESULTS

From Study 1 to 2, the prevalence of confirmed tinnitus reduced from 28.8% (49/170) to 14.9% (8/54) in retested subjects, which includes the cases of persisting tinnitus (confirmed tinnitus in both studies, n=6/54=11.2%) and the new cases of tinnitus (confirmed tinnitus just at Study 2, n=2/54=3.7%). Among the 15 adolescents with confirmed tinnitus at Study 1 who returned for Study 2, 40% had persistent tinnitus (n=6) and 60% did not (remitted tinnitus, n=9). SLT was reduced by 17.3dB in cases with persistent tinnitus (P<0.0002), similar to the findings of Study 1, and returned to normal levels in subjects with remitted tinnitus. Hearing thresholds averaged 4.37dBHL and were <20dBHL in 97% of ears and all frequencies. At 14 and 16kHz thresholds were bilaterally elevated at Study 1 (5.07dB) and 2 (5.56dB) in adolescents with confirmed tinnitus.

CONCLUSIONS

Tinnitus and reduced sound tolerance could feature early signals of hidden synaptic injury that is prevalent among adolescents and hidden from the audiogram. The strong relationship between both symptoms, in addition to low-level increases in hearing thresholds at high frequencies in the extended audiogram, poses a challenge for future hearing health and should be further evaluated as a possible intrinsic vulnerability for lesions following exposure to loud sounds. Moreover, the relationship between their spontaneous remissions may signal a possible synaptic repair, which has been reported in animal models.

Auditory Neural Plasticity in Tinnitus Mechanisms and Management

Tinnitus, which is the perception of sound in the absence of a corresponding external acoustic stimulus, including change of hearing and neural plasticity, has become an increasingly important ailment affecting the daily life of a considerable proportion of the population and causing significant burdens for both the affected individuals and society as a whole. Here, we briefly review the epidemiology and classification of tinnitus, and the currently available treatments are discussed in terms of the available evidence for their mechanisms and efficacy. The conclusion drawn from the available evidence is that there is no specific medication for tinnitus treatment at present, and tinnitus management might provide better solutions. Therapeutic interventions for tinnitus should be based on a comprehensive understanding of the etiology and features of individual cases of tinnitus, and more high quality and large-scale research studies are urgently needed to develop more efficacious medications.

Non-Invasive Neuromodulation for Tinnitus

Tinnitus is a prevalent disorder that has no cure currently. Within the last two decades, neuroscientific research has facilitated a better understanding of the pathophysiological mechanisms that underlie the generation and maintenance of tinnitus, and the brain and nerves have been identified as potential targets for its treatment using non-invasive brain stimulation methods. This article reviews studies on tinnitus patients using transcranial magnetic stimulation, transcranial electrical stimulation, such as transcranial direct current stimulation, alternating current stimulation, transcranial random noise stimulation as well as transcutaneous vagus nerve stimulation and bimodal combined auditory and somatosensory stimulation. Although none of these approaches has demonstrated effects that would justify its use in routine treatment, the studies have provided important insights into tinnitus pathophysiology. Moreover bimodal stimulation, which has only been developed recently, has shown promising results in pilot trials and is a candidate for further development into a valuable treatment procedure.

Impact of Acamprosate on Chronic Tinnitus: A Randomized-Controlled Trial

OBJECTIVES

Tinnitus is a common and distressing otologic symptom, with various probable pathophysiologic mechanisms, such as an imbalance between excitatory and inhibitory mechanisms. Acamprosate, generally used to treat alcoholism, is a glutaminergic antagonist and GABA agonist suggested for treating tinnitus. Thus, we aimed to evaluate the efficacy and safety of acamprosate in the treatment of tinnitus.

METHODS

The current randomized-controlled trial study included 20 subjects with chronic tinnitus. After performing psycho-acoustic, psychometric and electrophysiological evaluations, all studied tinnitus subjects were randomly divided into two groups of acamprosate and placebo. The first group received oral acamprosate (two tablets of 333 mg/d, three times a day), whereas the second group was given placebo treatment (two tablets, three times a day). After the first 30 days, all evaluations were repeated for the studied groups just in the same manner before the study. Subsequently, the final results of each evaluation were compared together with the baseline values.

RESULTS

Nine studied subjects randomly received acamprosate, whereas eleven others received a placebo. There was no significant improvement in the psycho-acoustic tests, except a decrease was observed in the pitch match of tinnitus (P = .039). For those subjects who were receiving acamprosate, a significant reduction was observed in tinnitus handicap inventory (P = .006), tinnitus questionnaire scores (P = .007), and the visual analog scores (P = .007) compared to the placebo group. There was a significant reduction in Action Potential latency (P = .048) as well as an increase in the amplitude of distortion product otoacoustic emissions at 4 kHz (P = .048).

CONCLUSIONS

The study results indicated a subjective relief of tinnitus as well as some degree of the electrophysiological improvement at the level of the cochlear and the distal portion of the auditory nerve among the subjects who received the acamprosate.

CLINICAL TRIAL REGISTRATION CODE

IRCT2013121115751N1.

Relationship between headaches and tinnitus in a Swedish study

The heterogeneity of tinnitus is likely accounting for the lack of effective treatment approaches. Headaches have been related to tinnitus, yet little is known on how headaches impact tinnitus. We use cross-sectional data from the Swedish Tinnitus Outreach Project to i) evaluate the association between headaches and tinnitus (n = 1,984 cases and 1,661 controls) and ii) investigate the phenotypic characteristics of tinnitus subjects with tinnitus (n = 660) or without (n = 1,879) headaches. In a multivariable logistic regression model, headache was significantly associated with any tinnitus (odds ratio, OR = 2.61) and more so with tinnitus as a big problem (as measured by the tinnitus functional index, TFI ≥ 48; OR = 5.63) or severe tinnitus (using the tinnitus handicap inventory, THI ≥ 58; OR = 4.99). When focusing on subjects with tinnitus, the prevalence of headaches was 26% and reached 40% in subjects with severe tinnitus. A large number of socioeconomic, phenotypic and psychological characteristics differed between headache and non-headache subjects with any tinnitus. With increasing tinnitus severity, fewer differences were found, the major ones being vertigo, neck pain and other pain syndromes, as well as stress and anxiety. Our study suggests that headaches could contribute to tinnitus distress and potentially its severity.

Binaural Interaction in Tinnitus Patients

The auditory brainstem response (ABR) is a commonly used objective clinical measure for hearing evaluation. It can be also used to draw conclusions about the functioning of distinct stages of the auditory pathway including the binaural processing stages using the binaural interaction component (BIC) of the ABR.

OBJECTIVE

To study binaural processing in normal hearing subjects complaining of tinnitus.

METHODS

Sixty cases with bilateral normal peripheral hearing were included in this work, divided into 2 groups, i.e., group 1 (comprised of 30 healthy subjects representing the control group) and group 2 (comprised of 30 subjects with tinnitus representing the study group). All of the subjects were submitted to a basic audiological evaluation (including pure tone audiometry, speech audiometry, and immittancemetry) and ABR audiometry recorded in monaural and then binaural conditions.

RESULTS

In monaural recording, the tinnitus group showed significantly delayed latencies of waves I, III, and V in addition to significantly reduced wave I and III amplitudes when compared with the controls. Similar significant findings were found when binaural ABR responses were compared between both groups. Comparing BIC between both groups showed significant earlier BIC for latencies of waves I and V in the control group, while the BIC for amplitudes showed similar results in both groups.

CONCLUSIONS

These finding suggest the presence of binaural processing deficits in tinnitus patients at different levels along the ascending auditory pathway.

Avenue for Future Tinnitus Treatments

Tinnitus is a common symptom. Standard therapies aim at improving the quality of life and reducing the psychological stress associated with tinnitus. Most interventions have little or no effect on the main symptom. Those affected subjects, however, want such a change and prefer a specific solution, such as pharmacologic therapy to other modalities. Scientific efforts have not yet led to significant improvement in the range of therapies. This article outlines existing efforts and develops ideas on how research for improved tinnitus therapy might look in the future.

Investigating functional changes in the brain to intermittently induced auditory illusions and its relevance to chronic tinnitus

Several studies have demonstrated the neural correlates of chronic tinnitus. However, we still do not understand what happens in the acute phase. Past studies have established Zwicker tone (ZT) illusions as a good human model for acute tinnitus. ZT illusions are perceived following the presentation of a notched noise stimulus, that is, broadband noise with a narrow band-stop filter (notch). In the current study, we compared the neural correlates of the reliable perception of a ZT illusion to that which is not. We observed changes in evoked and total theta power in wide-spread regions of the brain particularly in the temporal-parietal junction, pregenual anterior cingulate cortex/ventromedial prefrontal cortex (pgACC/vmPFC), parahippocampus during perception of the ZT illusion. Furthermore, we observe that increased theta power significantly predicts a gradual positive change in the intensity of the ZT illusion. Such changes may suggest a malfunction of the sensory gating system that enables habituation to redundant stimuli and suppresses hyperactivity. It could also suggest a successful retrieval of the memory of the missing frequencies, resulting in their conscious perception indicating the role of higher-order processing in the mechanism of action of ZT illusions. To establish a more concrete relationship between ZT illusion and chronic tinnitus, future longitudinal studies following up a much larger sample of participants who reliably perceive a ZT illusion to see if they develop tinnitus at a later stage is essential. This could inform us if the ZT illusion may be a precursor to chronic tinnitus.

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.

Noise: Acoustic Trauma and Tinnitus, the US Military Experience

Tinnitus is commonly experienced by military Service Members and Veterans, especially by the newest generation who served in Iraq and Afghanistan. When patients seek health care for tinnitus, it is important to determine its type, check for comorbid conditions that might be triggering or exacerbating the condition, and to address its functional and psychosocial effects. Otolaryngologists are usually the first health care professional to evaluate a patient with tinnitus, and it is essential to provide appropriate referrals for this high-burden condition. Noise-induced tinnitus is multifaceted; by performing a thorough assessment, appropriate action can be taken to best meet the needs of patients.

Current Device-based Clinical Treatments for Tinnitus

Device-based clinical treatments for tinnitus are predominantly sound based and include ear-level sound generators, hearing aids, cochlear implants, and tinnitus treatment devices. They are intended for patients with bothersome tinnitus. Bothersome tinnitus is characterized by problems with sleep, concentration, and mood. Most people with bothersome tinnitus have hearing loss and would benefit from amplification; however, not all patients are willing to use hearing aids. Tinnitus treatment devices are available to assist those who are not good candidates for amplification, and include devices used while sleeping and devices used for specified periods during the day.

Accounting for Heterogeneity: Mixed-Effects Models in Resting-State EEG Data in a Sample of Tinnitus Sufferers

In neuroscience, neural oscillations and other features of brain activity recorded by electroencephalography (EEG) are typically statistically assessed on the basis of the study’s population mean to identify possible blueprints for healthy subjects, or subjects with diagnosable neurological or psychiatric disorders. Despite some inter-individual similarities, there is reason to believe that a discernible portion of the individual brain activity is subject-specific. In order to encompass the potential individual source of variance in EEG data and psychometric parameters, we introduce an innovative application of linear mixed-effects models (LMM) as an alternative procedure for the analysis of resting-state EEG data. Using LMM, individual differences can be modelled through the assumptions of idiosyncrasy of all responses and dependency among data points (e.g., from the same subject within and across units of time) via random effects parameters. This report provides an example of how LMM can be used for the statistical analysis of resting-state EEG data in a heterogeneous group of subjects; namely, people who suffer from tinnitus (ringing in the ear/s). Results from 49 participants (38 male, mean age of 46.69 ± 12.65 years) revealed that EEG signals were not only associated with specific recording sites, but exhibited regional specific oscillations in conjunction to symptom severity. Tinnitus distress targeted the frequency bands beta3 (23.5–35 Hz) and gamma (35.5–45 Hz) in right frontal regions, whereas delta (0.5–4 Hz) exhibited significant changes in temporal-parietal sources. Further, 57.8% of the total variance in EEG power was subject-specific and acknowledged by the LMM framework and its prediction. Thus, a deeper understanding of both the underlying statistical and physiological patterns of EEG data was gained.

Animal Models of Tinnitus: A Review

Animal models have significantly contributed to understanding the pathophysiology of chronic subjective tinnitus. They are useful because they control etiology, which in humans is heterogeneous; employ random group assignment; and often use methods not permissible in human studies. Animal models can be broadly categorized as either operant or reflexive, based on methodology. Operant methods use variants of established psychophysical procedures to reveal what an animal hears. Reflexive methods do the same using elicited behavior, for example, the acoustic startle reflex. All methods contrast the absence of sound and presence of sound, because tinnitus cannot by definition be perceived as silence.

Regulation of auditory plasticity during critical periods and following hearing loss

Sensory input has profound effects on neuronal organization and sensory maps in the brain. The mechanisms regulating plasticity of the auditory pathway have been revealed by examining the consequences of altered auditory input during both developmental critical periods—when plasticity facilitates the optimization of neural circuits in concert with the external environment—and in adulthood—when hearing loss is linked to the generation of tinnitus. In this review, we summarize research identifying the molecular, cellular, and circuit-level mechanisms regulating neuronal organization and tonotopic map plasticity during developmental critical periods and in adulthood. These mechanisms are shared in both the juvenile and adult brain and along the length of the auditory pathway, where they serve to regulate disinhibitory networks, synaptic structure and function, as well as structural barriers to plasticity. Regulation of plasticity also involves both neuromodulatory circuits, which link plasticity with learning and attention, as well as ascending and descending auditory circuits, which link the auditory cortex and lower structures. Further work identifying the interplay of molecular and cellular mechanisms associating hearing loss-induced plasticity with tinnitus will continue to advance our understanding of this disorder and lead to new approaches to its treatment.

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During CPs, brain plasticity is enhanced and sensitive to acoustic experience.

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Enhanced plasticity can be reinstated in the adult brain following hearing loss.

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Molecular, cellular, and circuit-level mechanisms regulate CP and adult plasticity.

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Plasticity resulting from hearing loss may contribute to the emergence of tinnitus.

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Modifying plasticity in the adult brain may offer new treatments for tinnitus.

Aberrant expression of Nav1.6 in the cochlear nucleus correlates with salicylate-induced tinnitus in rats

Hyperactivity in cochlear nucleus (CN) is one of the major neural correlates for tinnitus induction, yet the molecular factors that participate in the neuronal hyperexcitability remain unclear. The present study showed that acute and chronic administrations of salicylate were both capable of inducing reversible tinnitus in rats. The number of GAD 65/67-immunoreactive neurons in the AVCN and DCN was decreased, while the number of VGLUT 1/2-immunoreactive neurons in the AVCN and DCN was increased when rats were experiencing tinnitus, providing evidence for excitatory-inhibitory imbalance in CN is correlated with tinnitus. Interestingly, the expression level of Nav1.6, an important subtype of voltage-gated sodium channels was significantly increased in the DCN and AVCN of rats experiencing tinnitus, the up-regulation of Nav1.6 was returned to normal level following the disappearance of tinnitus. Double-labeling experiments revealed that Nav1.6 expression was down-regulated in the GAD 65/67-positive neurons in the DCN and AVCN of rats experiencing tinnitus. Notably, the percentage of co-localization of Nav1.6 and NeuN-labeling fusiform neurons was markedly increased in the DCN during tinnitus. These findings uncover the tinnitus-associated alteration in Nav1.6, a potential key contributor that can lead to hyperexcitability in CN and contribute to salicylate-induced tinnitus.

[Analysis of comorbid psychiatric disorders in patients with chronic otitis media associated tinnitus]

Objective:To analyze the distribution of comorbid psychiatric disorders in patients with chronic otitis media associated tinnitus. Method:The data of patients with chronic otitis media associated tinnitus who accepted surgical treatments from July 2017 to September 2018 were retrospectively analyzed. All patients accepted pure tone audiometry and acoustic conductance examination and were requested to fill the tinnitus history questionnaire, THI, TEQ, SAS, SDS and PSQI scales before operation. When the SAS or/and SDS score ≥50 the patient was judged as having comorbid psychiatric disorders. When the PSQI score>6 the patient was judged as having comorbid sleep disorder, and then all the results were analyzed. Result:Sixty-two patients were included in the study, 43 cases were diagnosed as chronic suppurative otitis media, and 19 cases were diagnosed as middle ear cholesteatoma. The average course of chronic otitis media or middle ear cholesteatoma was（14.38±14.06） years, while the average course of tinnitus was（8.39±11.69） years. There were 32 cases with mild to moderate tinnitus（gradeⅠ-Ⅱ）（51.61%） and 30 cases with moderate to severe tinnitus（grade Ⅲ-Ⅴ）（48.39%）. Before operation, there were 4 cases（6.45%） with normal hearing, 38 cases（61.29%） with conductive hearing loss, and 20 cases（32.36%） with mixed hearing loss. There was no significant difference in tinnitus severity between different hearing loss degrees and types（P>0.05）. The average SAS score was 45.10±11.61, and the average SDS score was 43.48±14.67, both higher than the normal modulus（30 points）, among which 27 cases（44.00%） comorbid psychiatric disorders. The THI score in patients with comorbid psychiatric disorders（57.85±21.1） was significantly higher than that in patients without comorbid psychiatric disorders（29.2±17.39）（P<0.05）. The PSQI score in patients with comorbid psychiatric disorders（8.86±3.47） was significantly higher than that of those without comorbid psychiatric disorders（6.24±2.54）（P<0.05）. Fifty-three patients were followed up for 0.5 to 1.8 years after operation, and in 43 cases the tinnitus was reduced or disappeared after operation（the effective rate was 81.13%）. There were no significant difference between patients in tinnitus relief group and those in tinnitus without relief group in age, sex, course of the disease, type of the disease, with or without comorbid psychiatric disorders and/or sleep disorder, postoperative hearing improvement. Conclusion:Comorbid psychiatric disorders are common in patients with chronic otitis media associated tinnitus and the tinnitus in patients with comorbid psychiatric disorders is significantly more serious than that those without. For the treatment of chronic otitis media associated tinnitus, besides surgery, the complications such as psychiatric and sleep disorders and so on should be evaluated and treated accordingly.

Single-Session of Combined tDCS-TMS May Increase Therapeutic Effects in Subjects With Tinnitus

To treat motor and psychiatric disorders, transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS) are used in clinics worldwide. We combined these two types of neuromodulation technique to increase the effective response of a single session of neuromodulation in subjective tinnitus. Eighty tinnitus subjects were split into four different treatment groups: tDCS, tDCS with sham TMS, tDCS-TMS, and TMS group. Subjects were given 1.5 mA tDCS on the bi-frontal area and TMS stimulated the contralateral single side of the temporo-parietal cortex with 200 pulses at 1 Hz stimulation. Comparing pre-treatment questionnaire scores to post-treatment questionnaire scores, all four groups showed statistically significant improvements. Although there was no significant difference among group comparison, the largest mean difference was shown in the combined group, especially for tinnitus intensity and tinnitus-related distress. Responders in the combined group were the highest for VAS intensity, with a maximum of 80% of twenty subjects. To summarize, dual-neuromodulation responders could consist of responders of frontal tDCS and temporal TMS. In addition, abnormal activity in the frontal or temporal area of the responders is presumed to be modulated by treatment and will be suggested as the target areas in future studies.

Apoptosis in the cochlear nucleus and inferior colliculus upon repeated noise exposure

The time course of apoptosis and the corresponding neuronal loss was previously shown in central auditory pathway of mice after a single noise exposure. However, repeated acoustic exposure is a major risk factor for noise-induced hearing loss. The present study investigated apoptosis by terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling (TUNEL) assay after a second noise trauma in the ventral and dorsal cochlear nucleus and central nucleus of the inferior colliculus. Mice [Naval Medical Research Institute (NMRI) strain] were noise exposed [115 dB sound pressure level, 5-20 kHz, 3 h) at day 0. A double group received the identical noise exposure a second time at day 7 post-exposure and apoptosis was either analyzed immediately (7-day group-double) or 1 week later (14-day group-double). Corresponding single exposure groups were chosen as controls. No differences in TUNEL were seen between 7-day or 14-day single and double-trauma groups. Interestingly, independent of the second noise exposure, apoptosis increased significantly in the 14-day groups compared to the 7-day groups in all investigated areas. It seems that the first noise trauma has a long-lasting effect on apoptotic mechanisms in the central auditory pathway that were not largely influenced by a second trauma. Homeostatic mechanisms induced by the first trauma might protect the central auditory pathway from further damage during a specific time slot. These results might help to understand the underlying mechanisms of different psychoacoustic phenomena in noise-induced hearing loss.

Tinnitus healthcare: a survey revealing extensive variation in opinion and practices across Europe

Tinnitus remains a scientific and clinical problem whereby, in spite of increasing knowledge on effective treatment and management for tinnitus, very little impact on clinical practice has been observed. There is evidence that prolonged, obscure and indirect referral trajectories persist in usual tinnitus care.

OBJECTIVE

It is widely acknowledged that efforts to change professional practice are more successful if barriers are identified and implementation activities are systematically tailored to the specific determinants of practice. The aim of this study was to administer a health service evaluation survey to scope current practice and knowledge of standards in tinnitus care across Europe. The purpose of this survey was to specifically inform the development process of a European clinical guideline that would be implementable in all European countries.

DESIGN

A health service evaluation survey was carried out.

SETTING

The survey was carried out online across Europe.

PARTICIPANTS

Clinical experts, researchers and policy-makers involved in national tinnitus healthcare and decision-making.

OUTCOME MEASURES

A survey was developed by the study steering group, piloted on clinicians from the TINNET network and underwent two iterations before being finalised. The survey was then administered to clinicians and policy-makers from 24 European countries.

RESULTS

Data collected from 625 respondents revealed significant differences in national healthcare structures, use of tinnitus definitions, opinions on characteristics of patients with tinnitus, assessment procedures and particularly in available treatment options. Differences between northern and eastern European countries were most notable.

CONCLUSIONS

Most European countries do not have national clinical guidelines for the management of tinnitus. Reflective of this, clinical practices in tinnitus healthcare vary dramatically across countries. This equates to inequities of care for people with tinnitus across Europe and an opportunity to introduce standards in the form of a European clinical guideline. This survey has highlighted important barriers and facilitators to the implementation of such a guideline.

Cognitive behavioural therapy for tinnitus

BACKGROUND

Tinnitus affects up to 21% of the adult population with an estimated 1% to 3% experiencing severe problems. Cognitive behavioural therapy (CBT) is a collection of psychological treatments based on the cognitive and behavioural traditions in psychology and often used to treat people suffering from tinnitus.

OBJECTIVES

To assess the effects and safety of CBT for tinnitus in adults.

SEARCH METHODS

The Cochrane ENT Information Specialist searched the ENT Trials Register; CENTRAL (2019, Issue 11); 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 25 November 2019.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of CBT versus no intervention, audiological care, tinnitus retraining therapy or any other active treatment in adult participants with tinnitus.

DATA COLLECTION AND ANALYSIS

We used the standard methodological procedures expected by Cochrane. Our primary outcomes were the impact of tinnitus on disease-specific quality of life and serious adverse effects. Our secondary outcomes were: depression, anxiety, general health-related quality of life, negatively biased interpretations of tinnitus and other adverse effects. We used GRADE to assess the certainty of evidence for each outcome.

MAIN RESULTS

We included 28 studies (mostly from Europe) with a total of 2733 participants. All participants had had tinnitus for at least three months and their average age ranged from 43 to 70 years. The duration of the CBT ranged from 3 to 22 weeks and it was mostly conducted in hospitals or online. There were four comparisons and we were interested in outcomes at end of treatment, and 6 and 12 months follow-up. The results below only refer to outcomes at end of treatment due to an absence of evidence at the other follow-up time points. CBT versus no intervention/wait list control Fourteen studies compared CBT with no intervention/wait list control. For the primary outcome, CBT may reduce the impact of tinnitus on quality of life at treatment end (standardised mean difference (SMD) -0.56, 95% confidence interval (CI) -0.83 to -0.30; 10 studies; 537 participants; low certainty). Re-expressed as a score on the Tinnitus Handicap Inventory (THI; range 0 to 100) this is equivalent to a score 10.91 points lower in the CBT group, with an estimated minimal clinically important difference (MCID) for this scale being 7 points. Seven studies, rated as moderate certainty, either reported or informed us via personal communication about serious adverse effects. CBT probably results in little or no difference in adverse effects: six studies reported none and in one study one participant in the CBT condition worsened (risk ratio (RR) 3.00, 95% CI 0.13 to 69.87). For the secondary outcomes, CBT may result in a slight reduction in depression (SMD -0.34, 95% CI-0.60 to -0.08; 8 studies; 502 participants; low certainty). However, we are uncertain whether CBT reduces anxiety, improves health-related quality of life or reduces negatively biased interpretations of tinnitus (all very low certainty). From seven studies, no other adverse effects were reported (moderate certainty). CBT versus audiological care Three studies compared CBT with audiological care. CBT probably reduces the impact of tinnitus on quality of life when compared with audiological care as measured by the THI (range 0 to 100; mean difference (MD) -5.65, 95% CI -9.79 to -1.50; 3 studies; 444 participants) (moderate certainty; MCID = 7 points). No serious adverse effects occurred in the two included studies reporting these, thus risk ratios were not calculated (moderate certainty). The evidence suggests that CBT may slightly reduce depression but may result in little or no difference in anxiety or health-related quality of life (all low certainty) when compared with audiological care. CBT may reduce negatively biased interpretations of tinnitus when compared with audiological care (low certainty). No other adverse effects were reported for either group (moderate certainty). CBT versus tinnitus retraining therapy (TRT) One study compared CBT with TRT (including bilateral sound generators as per TRT protocol). CBT may reduce the impact of tinnitus on quality of life as measured by the THI when compared with TRT (range 0 to 100) (MD -15.79, 95% CI -27.91 to -3.67; 1 study; 42 participants; low certainty). For serious adverse effects three participants deteriorated during the study: one in the CBT (n = 22) and two in the TRT group (n = 20) (RR 0.45, 95% CI 0.04 to 4.64; low certainty). We are uncertain whether CBT reduces depression and anxiety or improves health-related quality of life (low certainty). CBT may reduce negatively biased interpretations of tinnitus. No data were available for other adverse effects. CBT versus other active control Sixteen studies compared CBT with another active control (e.g. relaxation, information, Internet-based discussion forums). CBT may reduce the impact of tinnitus on quality of life when compared with other active treatments (SMD -0.30, 95% CI -0.55 to -0.05; 12 studies; 966 participants; low certainty). Re-expressed as a THI score this is equivalent to 5.84 points lower in the CBT group than the other active control group (MCID = 7 points). One study reported that three participants deteriorated: one in the CBT and two in the information only group (RR 1.70, 95% CI 0.16 to 18.36; low certainty). CBT may reduce depression and anxiety (both low certainty). We are uncertain whether CBT improves health-related quality of life compared with other control. CBT probably reduces negatively biased interpretations of tinnitus compared with other treatments. No data were available for other adverse effects.

AUTHORS' CONCLUSIONS

CBT may be effective in reducing the negative impact that tinnitus can have on quality of life. There is, however, an absence of evidence at 6 or 12 months follow-up. There is also some evidence that adverse effects may be rare in adults with tinnitus receiving CBT, but this could be further investigated. CBT for tinnitus may have small additional benefit in reducing symptoms of depression although uncertainty remains due to concerns about the quality of the evidence. Overall, there is limited evidence for CBT for tinnitus improving anxiety, health-related quality of life or negatively biased interpretations of tinnitus.

Expression and Localization of Kv1.1 and Kv3.1b Potassium Channels in the Cochlear Nucleus and Inferior Colliculus after Long-Term Auditory Deafferentation

Deafness affects the expression and distribution of voltage-dependent potassium channels (Kvs) of central auditory neurons in the short-term, i.e., hours to days, but the consequences in the expression of Kvs after long-term deafness remain unknown. We tested expression and distribution of Kv1.1 and Kv3.1b, key for auditory processing, in the rat cochlear nucleus (CN), and in the inferior colliculus (IC), at 1, 15 and 90 days after mechanical lesion of the cochlea, using a combination of qRT-PCR and Western blot in the whole CN, along with semi-quantitative immunocytochemistry in the AVCN, where the role of both Kvs in the control of excitability for accurate auditory timing signal processing is well established. Neither Kv1.1/Kv3.1b mRNA or protein expression changed significantly in the CN between 1 and 15 days after deafness. At 90 days post-lesion, however, mRNA and protein expression for both Kvs increased, suggesting that regulation of Kv1.1 and Kv3.1b expression is part of cellular mechanisms for long-term adaptation to auditory deprivation in the CN. Consistent with these findings, immunocytochemistry showed increased labeling intensity for both Kvs in the AVCN at day 90 after cochlear lesion. This increase argues that up-regulation of Kv1.1 and Kv3.1b in AVCN neurons may be required to adapt intrinsic excitability to altered input over the long term after auditory deprivation. Contrary to these findings in the CN, expression levels of Kv1.1 and Kv3.1b in the IC did not undergo major changes after cochlear lesion. In particular, there was no evidence of long-term up-regulation of either Kv1.1 or Kv3.1b, supporting that such post-lesion adaptive mechanism may not be needed in the IC. These results reveal that post-lesion adaptations do not necessarily involve stereotyped plastic mechanisms along the entire auditory pathway.

Sense and Sensibility: A Review of the Behavioral Neuroscience of Tinnitus Sound Therapy and a New Typology

Tinnitus Sound Therapy is not a single strategy. It consists of many different sound types, targeting many different mechanisms. Therapies that use sound to cover, reduce attention to, or facilitate habituation of tinnitus are among the most common tinnitus treatment paradigms. Recent history has seen a proliferation of sound therapies, but they have each been criticized for having limited empirical support. In this review, Sound Therapy's modern history will be described, and a typology will be introduced and discussed in light of current behavioral neuroscience research. It will be argued that contributing factors to the limited evidence for the efficacy of Sound Therapy are its diversity, plural modes of action, and absence of a clear typology. Despite gaps in understanding the efficacy of sound's effects on tinnitus, there is compelling evidence for its multiple, but related, neurophysiological mechanisms. Evidence suggests that sound may reduce tinnitus through its presence, context, reaction, and potentially adaptation. This review provides insights into the neurocognitive basis of these tinnitus Sound Therapy modes. It concludes that a unifying classification is needed to secure and advance arguments in favor of Sound Therapy.

Pharmacotherapy of Tinnitus

Tinnitus is a common symptom for which there is in most cases no causal therapy. The search for an improvement of tinnitus through pharmacological interventions has a long tradition. The observation that tinnitus can be transiently suppressed by the use of lidocaine has shown that the symptom is susceptible to pharmacotherapy. So far, however, no medication has been found for either acute or chronic subjective tinnitus that reliably leads to a long-term reduction or even complete disappearance of the symptom for the majority of tinnitus sufferers. Nevertheless, in everyday clinical life, drugs are frequently used, usually off-label, to relieve tinnitus or tinnitus-associated symptoms (e.g. sleep disturbance, depression, anxiety disorder or hearing loss). This chapter shows the different approaches to acute and chronic subjective tinnitus by means of pharmacotherapeutic interventions. Furthermore, this review reports on the scientific studies carried out in this area in recent years and explains the difficulties in finding a suitable medication for most forms of tinnitus. In addition, it reports on the pharmacotherapeutic options for objective tinnitus and describes the development of tinnitus as a side effect of certain drugs. Finally, possible target structures are mentioned, which should possibly be addressed in pharmacological studies in the near future.

Diagnosis of Tinnitus Due to Auditory Radiation Injury Following Whiplash Injury: A Case Study

We report on a patient with tinnitus who showed injury of auditory radiation following whiplash injury, demonstrated by diffusion tensor tractography (DTT). A 48-year-old male patient suffered from a car crash resulting in flexion-hyperextension injury of his head after being hit from behind by a moving car while waiting at a signal while driving a car. Three days after the car crash, he began to feel tinnitus in both ears and his tinnitus became aggravated with the passage of time. No specific lesion was observed on a conventional brain MRI performed two weeks after the car crash. Although he visited several hospitals, the precise cause of his tinnitus was not detected. Two years after the car crash, he underwent evaluation for his tinnitus at the ear, nose and throat department of a university hospital. The pure tone audiometry was evaluated in a sound-proof room to screen his hearing status for the frequencies of 250-8000 Hz and no specific abnormality was detected. Although he was also tested for speech audiometry, there was also no specific abnormality. In order to assess his tinnitus, a tinnitogram was conducted to evaluate the frequency content and the loudness. His tinnitus was characterized at an intensity of 40 dB and a frequency of 4000 Hz. However, no abnormality was observed in either ear on physical examination. On DTT, the auditory radiation showed severe narrowing and tearing in both hemispheres. To summarize, neural injury of the auditory radiation was demonstrated in a patient with tinnitus following whiplash injury, using DTT.

Tinnitus Correlates with Downregulation of Cortical Glutamate Decarboxylase 65 Expression But Not Auditory Cortical Map Reorganization

Hearing loss is the biggest risk factor for tinnitus, and hearing-loss-related pathological changes in the auditory pathway have been hypothesized as the mechanism underlying tinnitus. However, due to the comorbidity of tinnitus and hearing loss, it has been difficult to differentiate between neural correlates of tinnitus and consequences of hearing loss. In this study, we dissociated tinnitus and hearing loss in FVB mice, which exhibit robust resistance to tinnitus following monaural noise-induced hearing loss. Furthermore, knock-down of glutamate decarboxylase 65 (GAD65) expression in auditory cortex (AI) by RNA interference gave rise to tinnitus in normal-hearing FVB mice. We found that tinnitus was significantly correlated with downregulation of GAD65 in the AI. By contrast, cortical map distortions, which have been hypothesized as a mechanism underlying tinnitus, were correlated with hearing loss but not tinnitus. Our findings suggest new strategies for the rehabilitation of tinnitus and other phantom sensation, such as phantom pain.SIGNIFICANCE STATEMENT Hearing loss is the biggest risk factor for tinnitus in humans. Most animal models of tinnitus also exhibit comorbid hearing loss, making it difficult to dissociate the mechanisms underlying tinnitus from mere consequences of hearing loss. Here we show that, although both C57BL/6 and FVB mice exhibited similar noise-induced hearing threshold increase, only C57BL/6, but not FVB, mice developed tinnitus following noise exposure. Although both strains showed frequency map reorganization following noise-induced hearing loss, only C57BL/6 mice had reduced glutamate decarboxylase 65 (GAD65) expression in the auditory cortex (AI). Knocking down GAD65 expression in the AI resulted in tinnitus in normal-hearing FVB mice. Our results suggest that reduced inhibitory neuronal function, but not sensory map reorganization, underlies noise-induced tinnitus.

Noninvasive Bimodal Neuromodulation for the Treatment of Tinnitus: Protocol for a Second Large-Scale Double-Blind Randomized Clinical Trial to Optimize Stimulation Parameters

Background

There is increasing evidence from animal and human studies that bimodal neuromodulation combining sound and electrical somatosensory stimulation of the tongue can induce extensive brain changes and treat tinnitus.

Objective

The main objectives of the proposed clinical study are to confirm the efficacy, safety, and tolerability of treatment demonstrated in a previous large-scale study of bimodal auditory and trigeminal nerve (tongue) stimulation (Treatment Evaluation of Neuromodulation for Tinnitus - Stage A1); evaluate the therapeutic effects of adjusting stimulation parameters over time; and determine the contribution of different features of bimodal stimulation in improving tinnitus outcomes.

Methods

This study will be a prospective, randomized, double-blind, parallel-arm, comparative clinical trial of a 12-week treatment for tinnitus using a Conformité Européenne (CE)–marked device with a pre-post and 12-month follow-up design. Four treatment arms will be investigated, in which each arm consists of two different stimulation settings, with the first setting presented during the first 6 weeks and the second setting presented during the next 6 weeks of treatment. The study will enroll 192 participants, split in a ratio of 80:80:16:16 across the four arms. Participants will be randomized to one of four arms and stratified to minimize baseline variability in four categories: two separate strata for sound level tolerance (using loudness discomfort level as indicators for hyperacusis severity), high tinnitus symptom severity based on the Tinnitus Handicap Inventory (THI), and tinnitus laterality. The primary efficacy endpoints are within-arm changes in THI and Tinnitus Functional Index as well as between-arm changes in THI after 6 weeks of treatment for the full cohort and two subgroups of tinnitus participants (ie, one hyperacusis subgroup and a high tinnitus symptom severity subgroup). Additional efficacy endpoints include within-arm or between-arm changes in THI after 6 or 12 weeks of treatment and in different subgroups of tinnitus participants as well as at posttreatment assessments at 6 weeks, 6 months, and 12 months. Treatment safety, attrition rates, and compliance rates will also be assessed and reported.

Results

This study protocol was approved by the Tallaght University Hospital/St. James’s Hospital Joint Research Ethics Committee in Dublin, Ireland. The first participant was enrolled on March 20, 2018. The data collection and database lock are expected to be completed by February 2020, and the data analysis and manuscript submission are expected to be conducted in autumn of 2020.

Conclusions

The findings of this study will be disseminated to relevant research, clinical, and health services and patient communities through publications in peer-reviewed journals and presentations at scientific and clinical conferences.

Trial Registration

ClinicalTrials.gov NCT03530306; https://clinicaltrials.gov/ct2/show/NCT03530306

International Registered Report Identifier (IRRID)

DERR1-10.2196/13176

Impact of Temporomandibular Joint Complaints on Tinnitus-Related Distress

There is increasing evidence of associations between the presence of temporomandibular joint (TMJ) disorders and tinnitus. It has been recently proposed that tinnitus patients with TMJ complaints could constitute a subtype, meaning a subgroup of tinnitus patients responsive to specific treatments. Tinnitus patients with TMJ complaints are often young women with somatosensory features of their tinnitus. Here, we investigate the socio-economic factors, phenotypic characteristics and psychological variables of tinnitus subjects from the Swedish Tinnitus Outreach Project, with (n = 486) or without (n = 1,996) TMJ complaints. The prevalence of TMJ complaints was greater in tinnitus subjects with severe tinnitus (36%) when compared to those with any tinnitus (19%), strongly indicating the contribution of TMJ problems to the severity of tinnitus. Comparing subgroups with or without TMJ complaints in the whole sample, differences were found regarding a large number of socioeconomic, phenotypic, and psychological characteristics. Subjects with TMJ complaints were more often women, more often reported stress as the cause of tinnitus, were more severely affected by tinnitus, scored worse in measures of psychological well-being and life quality, and were more often affected by problems tolerating sounds, headache, vertigo/dizziness, and neck pain. In addition, they more often reported pulsating and tonal tinnitus, somatic modulation of tinnitus, and aggravation of tinnitus by loud sounds and stress. When focusing the analysis in subjects with tinnitus as a big problem using the Tinnitus Functional Index cut-off ≥ 48, or with severe tinnitus according to the Tinnitus Handicap Inventory cut-off ≥ 58, the impact of somatosensory modulations and stress on tinnitus were greater in subjects with TMJ complaints in comparison to those without. In light of these results, we hypothesize that stress could contribute to the co-occurrence of TMJ problems and tinnitus and also to the development of severe tinnitus. Our study supports the need of involving dental care and stress management in the holistic treatment of patients with severe tinnitus.

Speech Comprehension and Its Relation to Other Auditory Parameters in Elderly Patients With Tinnitus

Deteriorated speech comprehension is a common manifestation of the age-related decline of auditory functions (presbycusis). It could be assumed that when presbycusis is accompanied by tinnitus, general hearing functions, and particularly comprehension of speech in quiet and speech in noise (SIN), will be significantly affected. In this study, speech comprehension ability and other parameters of auditory function were assessed in elderly subjects with (T, n = 25) and without (NT, n = 26) tinnitus, aiming for examination of both peripheral and central auditory processing. Apart from high-frequency audiograms in quiet and in background noise, speech recognition thresholds in silence or in competitive babble noise, and the ability to understand temporally gated speech (GS), we measured also sensitivity to frequency modulation (FM) and interaural delay, gap detection thresholds (GDT), or the difference limens of intensity. The results show that in elderly participants matched by age (mean ages around 68 years), cognitive status (median MoCA scores around 27), and hearing thresholds [median pure-tone averages (PTA) around 16 dB hearing loss (HL)], tinnitus per se has little influence on speech comprehension. The tinnitus patients also show similar GDT, sensitivity to interaural intensity difference, and sensitivity to FM as the NT subjects. Despite these similarities, nevertheless, significant differences in auditory processing have been found in the tinnitus participants: a worse ability to detect tones in noise, a higher sensitivity to intensity changes, and a higher sensitivity to interaural time differences. Additional correlation analyses further revealed that speech comprehension in the T subjects is dependent on the sensitivity to temporal modulation and interaural time delay (ITD), while these correlations are weak and non-significant in the NT subjects. Therefore, despite similarities in average speech comprehension and several other parameters of auditory function, elderly people with tinnitus exhibit different auditory processing, particularly at a suprathreshold level. The results also suggest that speech comprehension ability of elderly tinnitus patients relies more on temporal features of the sound stimuli, especially under difficult conditions, compared to elderly people without tinnitus.

Axonal sprouting in the dorsal cochlear nucleus affects gap‑prepulse inhibition following noise exposure

One of the primary theories of the pathogenesis of tinnitus involves maladaptive auditory-somatosensory plasticity in the dorsal cochlear nucleus (DCN), which is assumed to be due to axonal sprouting. Although a disrupted balance between auditory and somatosensory inputs may occur following hearing damage and may induce tinnitus, examination of this phenomenon employed a model of hearing damage that does not account for the causal relationship between these changes and tinnitus. The present study aimed to investigate changes in auditory-somatosensory innervation and the role that axonal sprouting serves in this process by comparing results between animals with and without tinnitus. Rats were exposed to a noise-inducing temporary threshold shift and were subsequently divided into tinnitus and non-tinnitus groups based on the results of gap prepulse inhibition of the acoustic startle reflex. DCNs were collected from rats divided into three sub-groups according to the number of weeks (1, 2 or 3) following noise exposure, and the protein levels of vesicular glutamate transporter 1 (VGLUT1), which is associated with auditory input to the DCN, and VGLUT2, which is in turn primarily associated with somatosensory inputs, were assessed. In addition, factors related to axonal sprouting, including growth-associated protein 43 (GAP43), postsynaptic density protein 95, synaptophysin, α-thalassemia/mental retardation syndrome X-linked homolog (ATRX), growth differentiation factor 10 (GDF10), and leucine-rich repeat and immunoglobulin domain-containing 1, were measured by western blot analyses. Compared to the non-tinnitus group, the tinnitus group exhibited a significant decrease in VGLUT1 at 1 week and a significant increase in VGLUT2 at 3 weeks post-exposure. In addition, rats in the tinnitus group exhibited significant increases in GAP43 and GDF10 protein expression levels in their DCN at 3 weeks following noise exposure. Results from the present study provided further evidence that changes in the neural input distribution to the DCN may cause tinnitus and that axonal sprouting underlies these alterations.

Recommendations on Collecting and Storing Samples for Genetic Studies in Hearing and Tinnitus Research

Objectives:

Research on the genetic basis of tinnitus is still in its first steps. A group of scientists dedicated to tinnitus genetics within European Tinnitus Network (TINNET) network recognize that further progress requires multicenter collaborative efforts for defining contributing genes. The purpose of the present work is to provide instructions regarding collection, processing, storage, and shipment of samples intended for genetic studies in auditory research.

Design:

One part of the recommendations has a general character; another part is of particular importance for auditory healthcare practitioners such as otolaryngology physicians, audiologists, and general practitioners.

Results:

We provide a set of instructions and various options for obtaining samples. We give advice regarding sample processing, storage, and shipment and define the minimal and essential clinical information that should accompany the samples collected for genetic processing.

Conclusions:

These recommendations offer a basis to standardize and optimize collaborations between geneticists and healthcare practitioners specialized in tinnitus and hearing disorders.

A comparative clinical study of arthrogenous versus myogenous temporomandibular disorder in patients presenting with Costen's syndrome

Objective: Costen's syndrome involves otoneurological and sinonasal symptoms associated with temporomandibular disorder (TMD). The current study compared the symptoms related to Costen's syndrome in patients with arthrogenous versus myogenous TMD.Methods: The study involved 294 consecutive patients with TMD, prospectively examined over a period of 6 months. These were stratified into 180 patients with arthrogenous TMD and 114 patients with myogenous TMD. A questionnaire and examination protocol was applied for each patient.Results: Sinonasal symptoms were more common in the arthrogenous group (p = .001), whereas, hearing loss and vertigo were more common in the myogenous group (p = .001).Conclusion: The current study provides support for central nervous system neuroplastic changes in the genesis of Costen's syndrome symptoms.

Sequential dual-site High-Definition transcranial Direct Current Stimulation (HD-tDCS) treatment in chronic subjective tinnitus: study protocol of a double-blind, randomized, placebo-controlled trial

Background

Chronic tinnitus is a highly prevalent symptom, with many patients reporting considerable effects of tinnitus on quality of life. No clear evidence-based treatment options are currently available. While counseling-based methods are valuable in some cases, they are not sufficiently effective for all tinnitus patients. Neuromodulation techniques such as high-definition transcranial direct current stimulation (HD-tDCS) are proposed to have positive effects on tinnitus severity but, to date, these effects have not been proven conclusively. The proposed trial will investigate the hypothesis that chronic tinnitus patients receiving HD-tDCS will report a positive effect on the impact of tinnitus on daily life, as compared to patients receiving sham stimulation.

Methods

This study proposes a randomized, double-blind, placebo-controlled trial with parallel group design. A total of 100 chronic tinnitus patients will be randomly allocated to an experimental group or a sham group, with allocation stratified according to gender and tinnitus severity. Patient and researcher will be blinded to the patient’s allocation. Patients will undergo six sessions of sequential dual-site HD-tDCS of the left temporal area and the right dorsolateral prefrontal cortex. Evaluations will take place at baseline, immediately following treatment, and at three and six months after the start of the therapy. The primary outcome measure is the change in Tinnitus Functional Index (TFI) score. Secondary outcome measures include audiological measurements, cortical auditory evoked potentials, the Repeatable Battery for the Assessment of Neuropsychological Status adjusted for hearing-impaired individuals (RBANS-H), and supplementary questionnaires probing tinnitus severity and additional symptoms. By use of a linear regression model, the effects of HD-tDCS compared to sham stimulation will be assessed.

Discussion

The objective of this study is to evaluate whether HD-tDCS can reduce the impact of tinnitus on daily life in chronic tinnitus patients. To date, published trials on the effects of HD-tDCS on tinnitus suffer from a lack of standardization and few randomized controlled trials exist. The proposed study will be the first adequately powered trial to investigate the effects of sequential dual-site HD-tDCS on tinnitus severity.

Trial registration

ClinicalTrials.gov, NCT03754127. Registered on 22 November 2018.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3594-y) contains supplementary material, which is available to authorized users.

Internally Generated Predictions Enhance Neural and Behavioral Detection of Sensory Stimuli in an Electric Fish

Studies of cerebellum-like circuits in fish have demonstrated that synaptic plasticity shapes the motor corollary discharge responses of granule cells into highly-specific predictions of self-generated sensory input. However, the functional significance of such predictions, known as negative images, has not been directly tested. Here we provide evidence for improvements in neural coding and behavioral detection of prey-like stimuli due to negative images. In addition, we find that manipulating synaptic plasticity leads to specific changes in circuit output that disrupt neural coding and detection of prey-like stimuli. These results link synaptic plasticity, neural coding, and behavior and also provide a circuit-level account of how combining external sensory input with internally generated predictions enhances sensory processing.

Altered gastric tone and motility response to brain-stem dopamine in a rat model of parkinsonism

The majority of patients with Parkinson's disease (PD) experience gastrointestinal dysfunction. Recently, we described a nigro-vagal pathway that uses dopaminergic (DA) inputs to the dorsal motor nucleus of the vagus (DMV) and A2 area neurons to modulate gastric motility and tone. This pathway is disrupted in a rodent model of PD. The aim of the present study was to test the hypothesis that brain-stem DA modulation of gastric tone and motility is altered in a rodent model of PD. Male Sprague-Dawley rats received three weekly intraperitoneal injections of paraquat (10 mg/kg) or saline (control). In naive conditions, microinjection of DA into the DMV induced a gastroinhibitory response in 100% of animals. In 19 of 28 PQ-treated animals, however, microinjection of DA into the DVC induced a biphasic response, with an initial increase in gastric tone and motility followed by a profound gastroinhibition. The excitatory response to DA microinjection was attenuated by a combination of DA type 1 (DA1)- and DA2-like receptor antagonists. Conversely, the inhibitory response was reduced by the DA2-like receptor antagonist only. Pretreatment with the α₂-adrenoceptor antagonist yohimbine did not modulate the response to DA, thus excluding involvement of the A2 area. At the end of the experiments, induction of the Parkinson phenotype was confirmed by the presence of α-synuclein immunoreactivity in the DMV and substantia nigra pars compacta. These data suggest a maladaptive neural plasticity in brain-stem vagal circuits regulating gastric motility in PQ-treated rats that may be responsible for the gastric dysfunction observed in PD models. NEW & NOTEWORTHY After paraquat treatment and induction of Parkinson's disease, brain-stem dopamine (DA) application induces a biphasic gastric response in the majority of rats, with an initial increase in tone and motility followed by gastroinhibition. The initial increase in gastric tone and motility is mediated via a combined activation of DA type 1 (DA1)- and DA2-like receptors. The inhibitory effects of DA are mediated by DA2-like receptors and are not affected by blockade of adrenergic inputs mediated by α₂-adrenoceptors.

[Differentiating cochlear synaptopathies into different hearing disorders]

Due to demographic change and altered recreational behavior, a rapid increase in hearing deficits is expected in the next 20-30 years. Consequently, the risk of age-related loss of speech discrimination, tinnitus, hyperacusis, or-as recently shown-dementia, will also increase. There are increasing indications that the loss of specific hearing fibers in humans and animals is involved in various hearing disorders. This fiber loss can be caused by cochlear synaptopathy or deafferentation and does not necessarily lead to clinically measurable threshold changes. Animal experiments have shown that reduced auditory nerve activity due to acoustic trauma or aging can be centrally compensated by disproportionately elevated and faster auditory brainstem responses (ABR). The analysis of the suprathreshold amplitudes of auditory evoked brain stem potentials and their latency in combination with non-invasive imaging techniques such as magnetic resonance imaging can help to identify the central compensatory ability of subjects and to assign defined hearing deficits.

Open(G)PIAS: An Open-Source Solution for the Construction of a High-Precision Acoustic Startle Response Setup for Tinnitus Screening and Threshold Estimation in Rodents

The modulation of the acoustic startle reflex (ASR) by a pre-stimulus called pre-pulse inhibition (PPI, for gap of silence pre-stimulus: GPIAS) is a versatile tool to, e.g., estimate hearing thresholds or identify subjective tinnitus percepts in rodents. A proper application of these paradigms depends on a reliable measurement of the ASR amplitudes and an exact stimulus presentation in terms of frequency and intensity. Here, we introduce a novel open-source solution for the construction of a low-cost ASR setup. The complete software for data acquisition and stimulus presentation is written in Python 3.6 and is provided as an Anaconda package. Furthermore, we provide a construction plan for the sensor system based on low-cost hardware components. Exemplary GPIAS data from two animal models (Mus musculus, Meriones unguiculatus) show that the ratio histograms (1-GPIAS) of the gap-pre-stimulus and no pre-stimulus ASR amplitudes can be well described by a log-normal distribution being in good accordance to previous studies with already established setups. Furthermore, it can be shown that the PPI as a function of pre-stimulus intensity (threshold paradigm) can be approximated with a hard-sigmoid function enabling a reproducible sensory threshold estimation. Thus, we show that the open-source solution could help to further establish the ASR method in many laboratories and, thus, facilitate and standardize research in animal models of tinnitus and/or hearing loss.

Severe Temporal Hyper-Activated States Caused by Noise in Tinnitus and Hyperacusis with Normal Hearing

Lots of neuroimaging and animal studies have revealed that tinnitus and hyperacusis share the same patterns in the bottom up central auditory process. The aim was to identify the abnormal central patterns commonly observed in both tinnitus and hyperacusis in humans. We investigated two cases of normal hearing: a tinnitus patient and a hyperacusis patient. We compared the differences between the severe temporal hyper-activated state (STHS), with spikes, fast beta and gamma frequencies after noise exposure, and the mild temporal hyper-activated state (MTHS), in no sound exposed condition. The power of the gamma band in the two cases was increased in both auditory cortices compared to the other brain regions. Our results of human with normal hearing were the first to identify how tinnitus and hyperacusis caused by sound are abnormally active and how they maintain constant pathological states.

Neuroinflammation mediates noise-induced synaptic imbalance and tinnitus in rodent models

Hearing loss is a major risk factor for tinnitus, hyperacusis, and central auditory processing disorder. Although recent studies indicate that hearing loss causes neuroinflammation in the auditory pathway, the mechanisms underlying hearing loss–related pathologies are still poorly understood. We examined neuroinflammation in the auditory cortex following noise-induced hearing loss (NIHL) and its role in tinnitus in rodent models. Our results indicate that NIHL is associated with elevated expression of proinflammatory cytokines and microglial activation—two defining features of neuroinflammatory responses—in the primary auditory cortex (AI). Genetic knockout of tumor necrosis factor alpha (TNF-α) or pharmacologically blocking TNF-α expression prevented neuroinflammation and ameliorated the behavioral phenotype associated with tinnitus in mice with NIHL. Conversely, infusion of TNF-α into AI resulted in behavioral signs of tinnitus in both wild-type and TNF-α knockout mice with normal hearing. Pharmacological depletion of microglia also prevented tinnitus in mice with NIHL. At the synaptic level, the frequency of miniature excitatory synaptic currents (mEPSCs) increased and that of miniature inhibitory synaptic currents (mIPSCs) decreased in AI pyramidal neurons in animals with NIHL. This excitatory-to-inhibitory synaptic imbalance was completely prevented by pharmacological blockade of TNF-α expression. These results implicate neuroinflammation as a therapeutic target for treating tinnitus and other hearing loss–related disorders.

Prolonged exposure to loud noises causes neuronal hyperexcitability and increases the risk of tinnitus. This study reveals that this type of tinnitus is mediated by noise-induced neuroinflammation; blockade of neuroinflammatory responses prevents noise-induced neuronal excitation/inhibition imbalance and tinnitus.

Neural plasticity and its initiating conditions in tinnitus

BACKGROUND AND OBJECTIVE

Deafferentation caused by cochlear pathology (which can be hidden from the audiogram) activates forms of neural plasticity in auditory pathways, generating tinnitus and its associated conditions including hyperacusis. This article discusses tinnitus mechanisms and suggests how these mechanisms may relate to those involved in normal auditory information processing.

MATERIALS AND METHODS

Research findings from animal models of tinnitus and from electromagnetic imaging of tinnitus patients are reviewed which pertain to the role of deafferentation and neural plasticity in tinnitus and hyperacusis.

RESULTS

Auditory neurons compensate for deafferentation by increasing their input/output functions (gain) at multiple levels of the auditory system. Forms of homeostatic plasticity are believed to be responsible for this neural change, which increases the spontaneous and driven activity of neurons in central auditory structures in animals expressing behavioral evidence of tinnitus. Another tinnitus correlate, increased neural synchrony among the affected neurons, is forged by spike-timing-dependent neural plasticity in auditory pathways. Slow oscillations generated by bursting thalamic neurons verified in tinnitus animals appear to modulate neural plasticity in the cortex, integrating tinnitus neural activity with information in brain regions supporting memory, emotion, and consciousness which exhibit increased metabolic activity in tinnitus patients.

DISCUSSION AND CONCLUSION

The latter process may be induced by transient auditory events in normal processing but it persists in tinnitus, driven by phantom signals from the auditory pathway. Several tinnitus therapies attempt to suppress tinnitus through plasticity, but repeated sessions will likely be needed to prevent tinnitus activity from returning owing to deafferentation as its initiating condition.