The neuroscience of tinnitus: understanding abnormal and normal auditory perception

Exploring the interplay of depression, sleep quality, and hearing in tinnitus-related handicap: insights from polysomnography and pure-tone audiometry

BACKGROUND

Tinnitus affects approximately 740 million adults globally, involving hearing, emotion, and sleep systems. However, studies using polysomnography and pure-tone audiometry (PTA) are limited. We aimed to assess the correlation between tinnitus and hearing, sleep quality, characteristics, and depression using polysomnography and PTA.

METHODS

In this cross-sectional study, we divided participants into tinnitus and non-tinnitus groups. We included 100 outpatients (65 with tinnitus, 35 without) from a medical center in Taiwan, who underwent polysomnography and completed rating scales including the Patient Health Questionnaire-9 (PHQ-9), Chinese version of the Pittsburgh Sleep Quality Index (PSQI), and Chinese-Mandarin version of the Tinnitus Handicap Inventory (THI-CM). We analyzed correlations, conducted group comparisons, assessed factors related to THI-CM scores, constructed ROC curves to predict depression in the tinnitus group, and performed multinomial and logistic regression to explore associations.

RESULTS

Descriptive statistics identified a cohort with mean age 53.9 ± 12.80 years, 63% exhibited PHQ-9 scores ≥ 10, and 66% had Apnea-Hypopnea Index (AHI) > 5. The ratio of rapid eye movement and deep sleep to stage 1 + 2 sleep was relatively low and non-significant. Likewise, leg movements was higher in the tinnitus group but not statistically significant. In the tinnitus group, 63.08% had depression, and 81.54% had AHI > 5. Univariate logistic regression linked tinnitus to AHI > 5 (Odds ratio (OR) 2.67, p = 0.026) and male sex (OR 2.49, p = 0.034). A moderate positive correlation was found between the THI-CM score and PHQ-9 score (rs = 0.50, p < 0.001). Further adjustment for obstructive sleep apnea showed associations between PHQ-9 (total score) or depression and THI-CM Grade 3-5 (OR = 1.28; OR = 8.68). Single- and multifactor regression analyses highlighted significant associations of PSQI scores > 13 (OR 7.06, p = 0.018) and THI-CM scores > 47 (OR 7.43, p = 0.002) with depression.

CONCLUSIONS

Our study recruited tinnitus participants with slight or mild hearing loss and mild tinnitus handicap. Depression was identified as a predominant factor in tinnitus-related handicap. The mild tinnitus handicap in tinnitus participants may explain the lack of significant differences in depression, sleep quality, and polysomnographic sleep characteristics between tinnitus and non-tinnitus groups. Further extensive and prospective studies are needed to elucidate the complex links among depression, sleep, and tinnitus.

Attention-Modulated Cortical Responses as a Biomarker for Tinnitus

Attention plays an important role in not only the awareness and perception of tinnitus but also its interactions with external sounds. Recent evidence suggests that attention is heightened in the tinnitus brain, likely as a result of relatively local cortical changes specific to deafferentation sites or global changes that help maintain normal cognitive capabilities in individuals with hearing loss. However, most electrophysiological studies have used passive listening paradigms to probe the tinnitus brain and produced mixed results in terms of finding a distinctive biomarker for tinnitus. Here, we designed a selective attention task, in which human adults attended to one of two interleaved tonal (500 Hz and 5 kHz) sequences. In total, 16 tinnitus (5 females) and 13 age- and hearing-matched control (8 females) subjects participated in the study, with the tinnitus subjects matching the tinnitus pitch to 5.4 kHz (range = 1.9-10.8 kHz). Cortical responses were recorded in both passive and attentive listening conditions, producing no differences in P1, N1, and P2 between the tinnitus and control subjects under any conditions. However, a different pattern of results emerged when the difference was examined between the attended and unattended responses. This attention-modulated cortical response was significantly greater in the tinnitus than control subjects: 3.9-times greater for N1 at 5 kHz (95% CI: 2.9 to 5.0, p = 0.007, ηp2 = 0.24) and 3.0 for P2 at 500 Hz (95% CI: 1.9 to 4.5, p = 0.026, ηp2 = 0.17). We interpreted the greater N1 modulation as local neural changes specific to the tinnitus frequency and the greater P2 as global changes to hearing loss. These two cortical measures were used to differentiate between the tinnitus and control subjects, producing 83.3% sensitivity and 76.9% specificity (AUC = 0.81, p = 0.006). These results suggest that the tinnitus brain is more plastic than that of the matched non-tinnitus controls and that the attention-modulated cortical response can be developed as a clinically meaningful biomarker for tinnitus.

Evaluation of Subjective Tinnitus Severity and Distortion Product Otoacoustic Emissions and Extended High-Frequency Audiometry

OBJECTIVE

Tinnitus is a multifactorial phenomenon with quality-of-life detriments for those affected by it. We aim to establish a relationship between subjective tinnitus severity with objective audiometric data in the extended high frequency (EHF) from 9 to 16 khz and with distortion product otoacoustic emissions (DPOAE). We hypothesize that severe subjective tinnitus as measured by the Tinnitus Handicap Inventory (THI) does not correlate with increased hearing thresholds in the EHF range.

STUDY DESIGN

Prospective.

SETTING

Single Tertiary Care Center.

METHODS

Patients identified with tinnitus and normal hearing thresholds within standard frequency range (250-8000 Hz) were consented for participation. Those with underlying otologic disease, trauma, radiotherapy, or ototoxic drug use were excluded. The THI questionnaire was given to eligible patients and audiometric test results were collected. THI scores were categorized by severity groups. An n = 20 to 30 was determined to have an effect size of 0.7 with a significance level of P = .05.

RESULTS

THI and audiometric data were collected for 38 patients and categorized into mild (n = 18, 47.4%), moderate (n = 8, 21.1%), slight (n = 7, 18.4%), and severe (n = 5, 13.2%) tinnitus severity groups. Mean THI score was 32.3 ± 19.6 with a statistically significant difference in scores by assigned THI severity group (P < .01). There were no significant differences or linear relationship among hearing thresholds in EHF range or DPOAE stratified by subjective tinnitus group (P = .49, r2 = 0.10) CONCLUSION: Subjective tinnitus severity is not predictive of audiometric outcomes. This finding can be used as a counseling tool to help tinnitus patients manage symptoms, expectations, and overall treatment outcomes.

Consensus Statements on the Definition, Classification, and Diagnostic Tests for Tinnitus: A Delphi Study Conducted by the Korean Tinnitus Study Group

BACKGROUND

Tinnitus is a bothersome condition associated with various symptoms. However, the mechanisms of tinnitus are still uncertain, and a standardized assessment of the diagnostic criteria for tinnitus is required. We aimed to reach a consensus on diagnosing tinnitus with professional experts by conducting a Delphi study with systematic review of the literature.

METHODS

Twenty-six experts in managing tinnitus in Korea were recruited, and a two-round modified Delphi study was performed online. The experts evaluated the level of agreement of potential criteria for tinnitus using a scale of 1-9. After the survey, a consensus meeting was held to establish agreement on the results obtained from the Delphi process. Consensus was defined when over 70% of the participants scored 7-9 (agreement) and fewer than 15% scored 1-3 (disagreement). To analyze the responses of the Delphi survey, the content validity ratio and Kendall's coefficient of concordance were evaluated.

RESULTS

Consensus was reached for 22 of the 38 statements. For the definition of tinnitus, 10 out of 17 statements reached consensus, with three statements achieving complete agreement including; 1) Tinnitus is a conscious perception of an auditory sensation in the absence of a corresponding external stimulus, 2) Tinnitus can affect one's quality of life, and 3) Tinnitus can be associated with hearing disorders including sensorineural hearing loss, vestibular schwannoma, Meniere's disease, otosclerosis, and others. For the classification of tinnitus, 11 out of 18 statements reached consensus. The participants highly agreed with statements such as; 1) Vascular origin is expected in pulse-synchronous tinnitus, and 2) Tinnitus can be divided into acute or chronic tinnitus. Among three statements on the diagnostic tests for tinnitus only Statement 3, "There are no reliable biomarkers for sensory or emotional factors of tinnitus." reached consensus. All participants agreed to perform pure-tone audiometry and tinnitus questionnaires, including the Tinnitus Handicap Inventory and Tinnitus Questionnaire.

CONCLUSION

We used a modified Delphi method to establish a consensus-based definition, a classification, and diagnostic tests for tinnitus. The expert panel reached agreement for several statements, with a high level of consensus. This may provide practical information for clinicians in managing tinnitus.

Cognition in vestibular disorders: state of the field, challenges, and priorities for the future

Vestibular disorders are prevalent and debilitating conditions of the inner ear and brain which affect balance, coordination, and the integration of multisensory inputs. A growing body of research has linked vestibular disorders to cognitive problems, most notably attention, visuospatial perception, spatial memory, and executive function. However, the mechanistic bases of these cognitive sequelae remain poorly defined, and there is a gap between our theoretical understanding of vestibular cognitive dysfunction, and how best to identify and manage this within clinical practice. This article takes stock of these shortcomings and provides recommendations and priorities for healthcare professionals who assess and treat vestibular disorders, and for researchers developing cognitive models and rehabilitation interventions. We highlight the importance of multidisciplinary collaboration for developing and evaluating clinically relevant theoretical models of vestibular cognition, to advance research and treatment.

Non-invasive brain stimulation for patients and healthy subjects: Current challenges and future perspectives

Non-invasive brain stimulation (NIBS) techniques have a rich historical background, yet their utilization has witnessed significant growth only recently. These techniques encompass transcranial electrical stimulation and transcranial magnetic stimulation, which were initially employed in neuroscience to explore the intricate relationship between the brain and behaviour. However, they are increasingly finding application in research contexts as a means to address various neurological, psychiatric, and neurodegenerative disorders. This article aims to fulfill two primary objectives. Firstly, it seeks to showcase the current state of the art in the clinical application of NIBS, highlighting how it can improve and complement existing treatments. Secondly, it provides a comprehensive overview of the utilization of NIBS in augmenting the brain function of healthy individuals, thereby enhancing their performance. Furthermore, the article delves into the points of convergence and divergence between these two techniques. It also addresses the existing challenges and future prospects associated with NIBS from ethical and research standpoints.

Help-seeker satisfaction with diagnosis and treatment of tinnitus

OBJECTIVE

To examine help-seeker satisfaction with the first communication of a tinnitus diagnosis by a healthcare provider, whether help-seekers undertook treatment and how they rated this treatment.

DESIGN

A survey design assessed tinnitus characteristics and distress, health status, help-seeking, diagnosis communication, treatment and patient satisfaction.

STUDY SAMPLE

A self-selected cohort and a population-based cohort.

RESULTS

Satisfaction scores were examined against demographic, clinical factors, and type of healthcare provider. A total of 281 adults participated (median age 61.6, IQR = 10.8 years), 52.3% sought help for tinnitus and 22.4% received treatment. The most frequently seen healthcare providers were general practitioners (34.0%), audiologists (29.3%) and ear, nose and throat specialists (25.9%). About two-thirds (64.1%) of help-seekers were unsatisfied with the first communication of a tinnitus diagnosis they received, and 56.5% rated their first tinnitus treatment as poor. Help-seekers were significantly more satisfied with audiologists than other providers regarding the communication of the first tinnitus diagnosis. Higher tinnitus distress scores were significantly associated with lower patient satisfaction with communication of first tinnitus diagnosis. No other factors were associated with patient satisfaction.

CONCLUSION

There are significant communication barriers along the tinnitus clinical pathway. Identifying and addressing these barriers could improve patient satisfaction.

EEG spectral and microstate analysis originating residual inhibition of tinnitus induced by tailor-made notched music training

Tailor-made notched music training (TMNMT) is a promising therapy for tinnitus. Residual inhibition (RI) is one of the few interventions that can temporarily inhibit tinnitus, which is a useful technique that can be applied to tinnitus research and explore tinnitus mechanisms. In this study, RI effect of TMNMT in tinnitus was investigated mainly using behavioral tests, EEG spectral and microstate analysis. To our knowledge, this study is the first to investigate RI effect of TMNMT. A total of 44 participants with tinnitus were divided into TMNMT group (22 participants; ECnm, NMnm, RInm represent that EEG recordings with eyes closed stimuli-pre, stimuli-ing, stimuli-post by TMNMT music, respectively) and Placebo control group (22 participants; ECpb, PBpb, RIpb represent that EEG recordings with eyes closed stimuli-pre, stimuli-ing, stimuli-post by Placebo music, respectively) in a single-blind manner. Behavioral tests, EEG spectral analysis (covering delta, theta, alpha, beta, gamma frequency bands) and microstate analysis (involving four microstate classes, A to D) were employed to evaluate RI effect of TMNMT. The results of the study showed that TMNMT had a stronger inhibition ability and longer inhibition time according to the behavioral tests compared to Placebo. Spectral analysis showed that RI effect of TMNMT increased significantly the power spectral density (PSD) of delta, theta bands and decreased significantly the PSD of alpha2 band, and microstate analysis showed that RI effect of TMNMT had shorter duration (microstate B, microstate C), higher Occurrence (microstate A, microstate C, microstate D), Coverage (microstate A) and transition probabilities (microstate A to microstate B, microstate A to microstate D and microstate D to microstate A). Meanwhile, RI effect of Placebo decreased significantly the PSD of alpha2 band, and microstate analysis showed that RI effect of Placebo had shorter duration (microstate C, microstate D), higher occurrence (microstate B, microstate C), lower coverage (microstate C, microstate D), higher transition probabilities (microstate A to microstate B, microstate B to microstate A). It was also found that the intensity of tinnitus symptoms was significant positively correlated with the duration of microstate B in five subgroups (ECnm, NMnm, RInm, ECpb, PBpb). Our study provided valuable experimental evidence and practical applications for the effectiveness of TMNMT as a novel music therapy for tinnitus. The observed stronger residual inhibition (RI) ability of TMNMT supported its potential applications in tinnitus treatment. Furthermore, the temporal dynamics of EEG microstates serve as novel functional and trait markers of synchronous brain activity that contribute to a deep understanding of the neural mechanism underlying TMNMT treatment for tinnitus.

Eavesdropping on Tinnitus Using MEG: Lessons Learned and Future Perspectives

Tinnitus has been widely investigated in order to draw conclusions about the underlying causes and altered neural activity in various brain regions. Existing studies have based their work on different tinnitus frameworks, ranging from a more local perspective on the auditory cortex to the inclusion of broader networks and various approaches towards tinnitus perception and distress. Magnetoencephalography (MEG) provides a powerful tool for efficiently investigating tinnitus and aberrant neural activity both spatially and temporally. However, results are inconclusive, and studies are rarely mapped to theoretical frameworks. The purpose of this review was to firstly introduce MEG to interested researchers and secondly provide a synopsis of the current state. We divided recent tinnitus research in MEG into study designs using resting state measurements and studies implementing tone stimulation paradigms. The studies were categorized based on their theoretical foundation, and we outlined shortcomings as well as inconsistencies within the different approaches. Finally, we provided future perspectives on how to benefit more efficiently from the enormous potential of MEG. We suggested novel approaches from a theoretical, conceptual, and methodological point of view to allow future research to obtain a more comprehensive understanding of tinnitus and its underlying processes.

Personalized Neuromodulation: A Novel Strategy for Improving Tinnitus Treatment

This study evaluated the efficacy of personalized neuromodulation, where treatment modalities are chosen based on the patient's responses in a pilot trial. A total of 71 patients with tinnitus were divided into two groups: a personalized group and a randomized neuromodulation group. In the personalized group (n = 35), repetitive transcranial magnetic stimulation (rTMS) and transcranial direct-current stimulation (tDCS) were assessed in a pilot trial, and responsive modalities were administered to 16 patients, while the non-responders (n = 19) were randomly assigned to rTMS, tDCS, or combined modalities. Patients in the randomized group (n = 36) were randomly allocated to rTMS, tDCS, or combined modalities. The Tinnitus Handicap Inventory (THI) score improvement after 10 sessions of each neuromodulation was significantly greater in the personalized group than in the randomized group (p = 0.043), with no significant differences in tinnitus loudness, distress, or awareness. The treatment success rate was highest in the personalized responder subgroup (92.3%), and significantly greater than that in the non-responder subgroup (53.0%; p = 0.042) and the randomized group (56.7%; p = 0.033). Personalized neuromodulation, where the treatment modality is chosen based on the patient's responses in a pilot trial, is an advantageous strategy for treating tinnitus.

Current and Emerging Therapies for Chronic Subjective Tinnitus

IMPORTANCE

Chronic subjective tinnitus, the perception of sound without an external source for longer than six months, may be a greatly debilitating condition for some people, and is associated with psychiatric comorbidities and high healthcare costs. Current treatments are not beneficial for all patients and there is a large need for new therapies for tinnitus.

OBSERVATIONS

Unlike rarer cases of objective tinnitus, chronic subjective tinnitus often has no obvious etiology and a diverse pathophysiology. In the absence of objective testing, diagnosis is heavily based on clinical assessment. Management strategies include hearing aids, sound masking, tinnitus retraining therapy, cognitive behavioral therapy, and emerging therapies including transcranial magnetic stimulation and electrical stimulation.

CONCLUSIONS AND RELEVANCE

Although current treatments are limited, emerging diagnostics and treatments provide promising avenues for the management of tinnitus symptoms.

Hearing Aids Combined With Educational Counseling Versus Educational Counseling Alone for Tinnitus Treatment in Patients With Hearing Loss: A Longitudinal Follow-Up Study

PURPOSE

The effect of hearing aids (HAs) and educational counseling (EC) or their combination on tinnitus is ambiguous. This study aimed to investigate whether the combined use of HAs and EC is more effective than EC alone on tinnitus relief.

METHOD

A total of 72 adults with chronic, bothersome tinnitus and coexisting sensorineural hearing loss completed at least 1-month and 3-month follow-up. After receiving EC and HA prescriptions, 21 participants selected to purchase HAs (i.e., the HA + EC group), whereas the remaining 51 refused to use HAs despite recommendations (i.e., the EC group). Tinnitus severity was measured by Tinnitus Handicap Inventory (THI), Tinnitus Evaluation Questionnaire (TEQ), and Visual Analog Scale (VAS) for loudness. The primary outcome measure was THI, and tinnitus relief was defined as a 20-point or more reduction in THI. A generalized linear mixed model was used to confirm that the heterogeneity in baseline characteristics between groups did not interfere with the results.

RESULTS

The THI, TEQ, and VAS scores decreased significantly after treatments, and both groups yielded a similar trend of reduction. There were no significant differences in the incidence of tinnitus relief and time-to-event curves between the two groups. In addition, the length of follow-up did not affect treatment effectiveness.

CONCLUSION

There was insufficient evidence to support the superiority of the combined use of HA and EC for tinnitus over EC with no device.

Amplification of the poorer ear by StereoBiCROS in case of asymmetric sensorineural hearing loss: effect on tinnitus

Tinnitus is prevalent among patients suffering from Single-Sided Deafness (SSD) and Asymmetrical Hearing Loss (AHL). In addition to bothersome tinnitus in the poorer ear, these patients also report issues with understanding speech in noise and sound localization. The conventional treatment options offered to these patients to improve auditory abilities are cochlear implantation, bone conduction devices or Contralateral Routing Of Signal (CROS) hearing aids. It was recently found that the benefit of cochlear implantation for tinnitus associated with AHL/SSD was greater than the other two approaches. It is conceivable that the lack of stimulation provided to the poorer ear in these last approaches explains their modest impact on tinnitus perception. A new technology that combines the ability to reroute the sound from the poorer ear to the good ear (CROS system) while still stimulating the poorer ear with conventional sound amplification has recently been developed: the StereoBiCROS system. The aim of this study was to investigate the effects of this new device on tinnitus. Twelve AHL and two SSD patients aged 70.7 ± 7.9 years with tinnitus were fitted with bilateral hearing aids that included 3 programs: Stereophonic, BiCROS and StereoBiCROS (CROS + bilateral amplification). The short-and long-term effect of the approach on tinnitus was assessed using a tinnitus Loudness Visual Analog Scale (VAS) and the Tinnitus Handicap Inventory (THI), respectively. Both the VAS and the THI were used before and one month after the hearing aid fitting. Of the 14 patients who used their hearing aids daily (12.6 ± 1.6 h per day) the StereoBiCROS program was the most used program (81.8 ± 20.5% of the time). The average THI total score decreased from 47 (± 22) to 15 (± 16) (p = 0.002) and the VAS-Loudness score decreased from 7 (± 1) to 2 (± 2) (p < 0.001) after the one-month trial period. In conclusion, StereoBiCROS stimulation strategy seems to offer an effective alternative to reduce tinnitus handicap and loudness for patients with AHL/SSD and tinnitus. This effect may be driven by sound amplification of the poorer ear.

Tinnitus at the Junction of Traditional Medicine and Modern Technology

The WHO estimated that 430 million people worldwide suffer from moderate-to-severe hearing loss [...].

Modelling homeostatic plasticity in the auditory cortex results in neural signatures of tinnitus

Tinnitus is a clinical condition where a sound is perceived without an external sound source. Homeostatic plasticity (HSP), serving to increase neural activity as compensation for the reduced input to the auditory pathway after hearing loss, has been proposed as a mechanism underlying tinnitus. In support, animal models of tinnitus show evidence of increased neural activity after hearing loss, including increased spontaneous and sound-driven firing rate, as well as increased neural noise throughout the auditory processing pathway. Bridging these findings to human tinnitus, however, has proven to be challenging. Here we implement hearing loss-induced HSP in a Wilson-Cowan Cortical Model of the auditory cortex to predict how homeostatic principles operating at the microscale translate to the meso- to macroscale accessible through human neuroimaging. We observed HSP-induced response changes in the model that were previously proposed as neural signatures of tinnitus, but that have also been reported as correlates of hearing loss and hyperacusis. As expected, HSP increased spontaneous and sound-driven responsiveness in hearing-loss affected frequency channels of the model. We furthermore observed evidence of increased neural noise and the appearance of spatiotemporal modulations in neural activity, which we discuss in light of recent human neuroimaging findings. Our computational model makes quantitative predictions that require experimental validation, and may thereby serve as the basis of future human studies of hearing loss, tinnitus, and hyperacusis.

A Protocol to Investigate Deep Brain Stimulation for Refractory Tinnitus: From Rat Model to the Set-Up of a Human Pilot Study

BACKGROUND

Chronic tinnitus can have an immense impact on quality of life. Despite recent treatment advances, many tinnitus patients remain refractory to them. Preclinical and clinical evidence suggests that deep brain stimulation (DBS) is a promising treatment to suppress tinnitus. In rats, it has been shown in multiple regions of the auditory pathway that DBS can have an alleviating effect on tinnitus. The thalamic medial geniculate body (MGB) takes a key position in the tinnitus network, shows pathophysiological hallmarks of tinnitus, and is readily accessible using stereotaxy. Here, a protocol is described to evaluate the safety and test the therapeutic effects of DBS in the MGB in severe tinnitus sufferers.

METHODS

Bilateral DBS of the MGB will be applied in a future study in six patients with severe and refractory tinnitus. A double-blinded, randomized 2 × 2 crossover design (stimulation ON and OFF) will be applied, followed by a period of six months of open-label follow-up. The primary focus is to assess safety and feasibility (acceptability). Secondary outcomes assess a potential treatment effect and include tinnitus severity measured by the Tinnitus Functional Index (TFI), tinnitus loudness and distress, hearing, cognitive and psychological functions, quality of life, and neurophysiological characteristics.

DISCUSSION

This protocol carefully balances risks and benefits and takes ethical considerations into account. This study will explore the safety and feasibility of DBS in severe refractory tinnitus, through extensive assessment of clinical and neurophysiological outcome measures. Additionally, important insights into the underlying mechanism of tinnitus and hearing function might be revealed.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03976908 (6 June 2019).

Sound Therapy to Reduce Auditory Gain for Hyperacusis and Tinnitus

Purpose:

Hyperacusis is the most common of the different types of sound tolerance conditions. It has been defined as physical discomfort or pain when any sound reaches a certain level of loudness that would be comfortable for most people. Because hyperacusis and tinnitus occur together so often, it has been theorized that they have a common neural mechanism. A leading contender for that mechanism is enhancement of auditory gain. The purpose of this tutorial is to review the evidence that sound/acoustic therapy can reduce auditory gain and, thereby, can increase loudness tolerance for people with hyperacusis and/or suppress the percept of tinnitus.

Method:

The scientific literature was informally reviewed to identify and elucidate relationships between tinnitus, hyperacusis, sound therapy, and auditory gain.

Results:

Evidence exists, both in animal and human studies, that enhanced auditory gain is associated with hyperacusis and tinnitus. Further evidence supports the theory that certain forms of sound therapy can reduce neural hyperactivity, thereby reducing auditory gain. The evidence for sound therapy reducing auditory gain is stronger for hyperacusis than it is for tinnitus.

Conclusions:

Based on results from numerous studies, sound therapy clearly has application as a method of desensitization for hyperacusis. Enhanced auditory gain might be responsible for tinnitus, but other mechanisms have been theorized. A review of the relevant literature leads to the conclusion that some form(s) of sound therapy has the potential to suppress or eliminate tinnitus on a long-term basis. Systematic research is needed to evaluate this premise.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Functional changes in the auditory cortex and associated regions caused by different acoustic stimuli in patients with presbycusis and tinnitus

Presbycusis and tinnitus are the two most common hearing related pathologies. Although both of these conditions presumably originate in the inner ear, there are several reports concerning their central components. Interestingly, the onset of presbycusis coincides with the highest occurrence of tinnitus. The aim of this study was to identify age, hearing loss, and tinnitus related functional changes, within the auditory system and its associated structures. Seventy-eight participants were selected for the study based on their age, hearing, and tinnitus, and they were divided into six groups: young controls (Y-NH-NT), subjects with mild presbycusis (O-NH-NT) or expressed presbycusis (O-HL-NT), young subjects with tinnitus (Y-NH-T), subjects with mild presbycusis and tinnitus (O-NH-T), and subjects with expressed presbycusis and tinnitus (O-HL-T). An MRI functional study was performed with a 3T MRI system, using an event related design (different types of acoustic and visual stimulations and their combinations). The amount of activation of the auditory cortices (ACs) was dependent on the complexity of the stimuli; higher complexity resulted in a larger area of the activated cortex. Auditory stimulation produced a slightly greater activation in the elderly, with a negative effect of hearing loss (lower activation). The congruent audiovisual stimulation led to an increased activity within the default mode network, whereas incongruent stimulation led to increased activation of the visual cortex. The presence of tinnitus increased activation of the AC, specifically in the aged population, with a slight prevalence in the left AC. The occurrence of tinnitus was accompanied by increased activity within the insula and hippocampus bilaterally. Overall, we can conclude that expressed presbycusis leads to a lower activation of the AC, compared to the elderly with normal hearing; aging itself leads to increased activity in the right AC. The complexity of acoustic stimuli plays a major role in the activation of the AC, its support by visual stimulation leads to minimal changes within the AC. Tinnitus causes changes in the activity of the limbic system, as well as in the auditory AC, where it is bound to the left hemisphere.

Random Forest Classification to Predict Response to High-Definition Transcranial Direct Current Stimulation for Tinnitus Relief: A Preliminary Feasibility Study

OBJECTIVES

Transcranial direct current stimulation (tDCS) of the right dorsolateral prefrontal cortex has been hypothesized to reduce tinnitus severity by modifying cortical activity in brain regions associated with the perception of tinnitus. However, individual response to tDCS has proven to be variable. We investigated the feasibility of using random forest classification to predict the response to high-definition (HD) tDCS for tinnitus relief.

DESIGN

A retrospective analysis was performed on a dataset consisting of 99 patients with subjective tinnitus receiving six consecutive sessions of HD-tDCS at the Antwerp University Hospital. A baseline assessment consisted of pure-tone audiometry and a set of questionnaires including the Tinnitus Functional Index (TFI), Hospital Anxiety and Depression Scale, and Edinburgh Handedness Inventory. Random forest classification was applied to predict, based on baseline questionnaire scores and hearing levels, whether each individual responded positively to the treatment (defined as a decrease of at least 13 points on the TFI). Further testing of the model was performed on an independent cohort of 32 patients obtained from the tinnitus center at the University of Regensburg.

RESULTS

Twenty-four participants responded positively to the HD-tDCS treatment. The random forest classifier predicted treatment response with an accuracy of 85.71% (100% sensitivity, 81.48% specificity), significantly outperforming a more traditional logistic regression approach. Performance of the classifier on an independent cohort was slightly but not significantly above chance level (71.88% accuracy, 66.67% sensitivity, 73.08% specificity). Feature importance analyses revealed that baseline tinnitus severity, co-occurrence of depressive symptoms and handedness were the most important predictors of treatment response. Baseline TFI scores were significantly higher in responders than in nonresponders.

CONCLUSIONS

The proposed random forest classifier predicted treatment response with a high accuracy, significantly outperforming a more traditional statistical approach. Machine learning methods to predict treatment response might ultimately be used in a clinical setting to guide targeted treatment recommendations for individual tinnitus patients.

Effect of Auditory Discrimination Therapy on Attentional Processes of Tinnitus Patients

Tinnitus is an auditory condition that causes humans to hear a sound anytime, anywhere. Chronic and refractory tinnitus is caused by an over synchronization of neurons. Sound has been applied as an alternative treatment to resynchronize neuronal activity. To date, various acoustic therapies have been proposed to treat tinnitus. However, the effect is not yet well understood. Therefore, the objective of this study is to establish an objective methodology using electroencephalography (EEG) signals to measure changes in attentional processes in patients with tinnitus treated with auditory discrimination therapy (ADT). To this aim, first, event-related (de-) synchronization (ERD/ERS) responses were mapped to extract the levels of synchronization related to the auditory recognition event. Second, the deep representations of the scalograms were extracted using a previously trained Convolutional Neural Network (CNN) architecture (MobileNet v2). Third, the deep spectrum features corresponding to the study datasets were analyzed to investigate performance in terms of attention and memory changes. The results proved strong evidence of the feasibility of ADT to treat tinnitus, which is possibly due to attentional redirection.

Objective Recognition of Tinnitus Location Using Electroencephalography Connectivity Features

Purpose: Tinnitus is a common but obscure auditory disease to be studied. This study will determine whether the connectivity features in electroencephalography (EEG) signals can be used as the biomarkers for an efficient and fast diagnosis method for chronic tinnitus.

Methods: In this study, the resting-state EEG signals of tinnitus patients with different tinnitus locations were recorded. Four connectivity features [including the Phase-locking value (PLV), Phase lag index (PLI), Pearson correlation coefficient (PCC), and Transfer entropy (TE)] and two time-frequency domain features in the EEG signals were extracted, and four machine learning algorithms, included two support vector machine models (SVM), a multi-layer perception network (MLP) and a convolutional neural network (CNN), were used based on the selected features to classify different possible tinnitus sources.

Results: Classification accuracy was highest when the SVM algorithm or the MLP algorithm was applied to the PCC feature sets, achieving final average classification accuracies of 99.42 or 99.1%, respectively. And based on the PLV feature, the classification result was also particularly good. And MLP ran the fastest, with an average computing time of only 4.2 s, which was more suitable than other methods when a real-time diagnosis was required.

Conclusion: Connectivity features of the resting-state EEG signals could characterize the differentiation of tinnitus location. The connectivity features (PCC and PLV) were more suitable as the biomarkers for the objective diagnosing of tinnitus. And the results were helpful for clinicians in the initial diagnosis of tinnitus.

Evaluating the efficacy of hearing aids for tinnitus therapy - A Positron emission tomography study

Brain imaging studies have revealed neural changes in chronic tinnitus patients that are not restricted to auditory brain areas; rather, the engagement of limbic system structures, attention and memory networks are has been noted. Hearing aids (HA) provide compensation for comorbid hearing loss and may decrease tinnitus-related perception and annoyance. Using resting state positron emission tomography our goal was to analyze metabolic and functional brain changes after six months of effective HA use by patients with chronic tinnitus and associated sensorineural hearing loss. 33 age and hearing loss matched participants with mild/moderate hearing loss were enrolled in this study: 19 with tinnitus, and 14 without tinnitus. Participants with tinnitus of more than 6 months with moderate/severe Tinnitus Handicap Inventory (THI) and Visual Analogue Scale (VAS) scores composed the tinnitus group. A full factorial 2X2 ANOVA was conducted for imaging analysis, with group (tinnitus and controls) and time point (pre-intervention and post-intervention) as factors. Six months after HA fitting, tinnitus scores reduced statistically and clinically. Analysis revealed increased glycolytic metabolism in the left orbitofrontal cortex, right temporal lobe and right hippocampus, and reduced glycolytic metabolism in the left cerebellum and inferior parietal lobe within the tinnitus group. The hearing loss control group showed no significant metabolic changes in the analysis. Parsing out the contribution of tinnitus independent of hearing loss, allowed us to identify areas implicated in declines in tinnitus handicap as a result of the intervention. Brain regions implicated in the present study may be part of chronic tinnitus-specific network.

The mismatch negativity responses of individuals with tinnitus with normal extended high-frequency hearing-is it possible to use mismatch negativity in the evaluation of tinnitus?

OBJECTIVE

This study uses the multi-feature paradigm to compare the MMN responses of individuals with normal hearing thresholds, including the high frequencies with and without tinnitus.

METHODS

Sixteen subjects with chronic subjective idiopathic tinnitus and twenty matched healthy controls were included in the study. Participants with hearing thresholds (0.125-16 kHz) less than 20 dB HL and MoCA test scores above 21 were included in the study. MMN responses and topographical maps of the responses resulting from the multi-feature MMN paradigm were recorded from 22 surface scalp electrodes. Amplitude and latency parameters of the MMN responses of five different deviants, consisting of frequency, intensity, duration, location, and silent gap, were compared between the two groups.

RESULTS

The amplitudes of MMN responses were lower in the tinnitus group than in the control group at Fz electrode for all deviant types. At the same time, there was no difference between the groups for MMN latencies and, no correlation was found between THI and MMN.

CONCLUSION

According to our results, the MMN might indicate a possible impairment in pre-attentive and automatic central auditory processing for chronic tinnitus patients. Since MMN responses in the tinnitus group differ from those of healthy individuals, it might be used as a reference for evaluating the central auditory pathways of tinnitus patients.

Heading for Personalized rTMS in Tinnitus: Reliability of Individualized Stimulation Protocols in Behavioral and Electrophysiological Responses

Background: Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive brain stimulation tool potentially modulating pathological brain activity. Its clinical effectiveness is hampered by varying results and characterized by inter-individual variability in treatment responses. RTMS individualization might constitute a useful strategy to overcome this variability. A precondition for this approach would be that repeatedly applied protocols result in reliable effects. The condition tinnitus provides the advantage of immediate behavioral consequences (tinnitus loudness changes) after interventions and thus offers an excellent model to exemplify TMS personalization. Objective: The aim was to investigate the test–retest reliability of short rTMS stimulations in modifying tinnitus loudness and oscillatory brain activity as well as to examine the feasibility of rTMS individualization in tinnitus. Methods: Three short verum (1, 10, 20 Hz; 200 pulses) and one sham (0.1 Hz; 20 pulses) rTMS protocol were administered on two different days in 22 tinnitus patients. Before and after each protocol, oscillatory brain activity was recorded with electroencephalography (EEG), together with behavioral tinnitus loudness ratings. RTMS individualization was executed on the basis of behavioral and electrophysiological responses. Stimulation responders were identified via consistent sham-superior increases in tinnitus loudness (behavioral responders) and alpha power increases or gamma power decreases (alpha responders/gamma responders) in accordance with the prevalent neurophysiological models for tinnitus. Results: It was feasible to identify individualized rTMS protocols featuring reliable tinnitus loudness changes (55% behavioral responder), alpha increases (91% alpha responder) and gamma decreases (100% gamma responder), respectively. Alpha responses primary occurred over parieto-occipital areas, whereas gamma responses mainly appeared over frontal regions. On the contrary, test–retest correlation analyses per protocol at a group level were not significant neither for behavioral nor for electrophysiological effects. No associations between behavioral and EEG responses were found. Conclusion: RTMS individualization via behavioral and electrophysiological data in tinnitus can be considered as a feasible approach to overcome low reliability at the group level. The present results open the discussion favoring personalization utilizing neurophysiological markers rather than behavioral responses. These insights are not only useful for the rTMS treatment of tinnitus but also for neuromodulation interventions in other pathologies, as our results suggest that the individualization of stimulation protocols is feasible despite absent group-level reliability.

The balance between Bayesian inference and default mode determines the generation of tinnitus from decreased auditory input: A volume entropy-based study

Along with phantom pain, tinnitus, a phantom auditory perception occurring in the absence of an external acoustic stimulus, is one of the most representative phantom perceptions that develops in subjects with decreased peripheral sensory input. Although tinnitus is closely associated with peripheral hearing loss (HL), it remains unclear why only some individuals with HL develop tinnitus. In this study, we investigated the differences between 65 HL with tinnitus (HL‐T) and 104 HL with no tinnitus (HL‐NT) using a resting‐state electroencephalography data‐based volume entropy model of the brain network, by comparing the afferent node capacities, that quantify the contribution of each node to the spread of information, of all Brodmann areas. While the HL‐T group showed increased information flow in areas involved in Bayesian inference (the left orbitofrontal cortex, the left subgenual anterior cingulate cortex, and the left ventrolateral prefrontal cortex) and auditory memory storage (the right hippocampus/parahippocampus), the HL‐NT group showed increased afferent node capacity in hub areas of the default mode network (DMN; the right posterior cingulate cortex and the right medial temporal gyrus). These results suggest that the balance of activity between the Bayesian inferential network (updating missing auditory information by retrieving auditory memories from the hippocampus/parahippocampus) and DMN (maintaining the “silent status quo”) determines whether phantom auditory perception occurs in a brain with decreased peripheral auditory input.

Neurophysiological correlates of residual inhibition in tinnitus: Hints for trait-like EEG power spectra

OBJECTIVE

To investigate oscillatory brain activity changes following acoustic stimulation in tinnitus and whether these changes are associated with behavioral measures of tinnitus loudness. Moreover, differences in ongoing brain activity between individuals with and without residual inhibition (RI) are examined (responders vs. non-responders).

METHODS

Three different types of noise stimuli were administered for acoustic stimulation in 45 tinnitus patients. Subjects resting state brain activity was recorded before and after stimulation via EEG alongside with subjective measurements of tinnitus loudness.

RESULTS

Delta, theta and gamma band power increased, whereas alpha and beta power decreased from pre to post stimulation. Acoustic stimulation responders exhibited reduced gamma and a trend for enhanced alpha activity with the latter localized in the right inferior temporal gyrus. Post stimulation, individuals experiencing RI showed higher theta, alpha and beta power with a peak power difference in the alpha band localized in the right superior temporal gyrus. Neither correlations with behavioral tinnitus measures nor stimulus-specific changes in EEG activity were present.

CONCLUSIONS

Our observations might be indicative of trait-specific forms of oscillatory signatures in different subsets of the tinnitus population related to acoustic tinnitus suppression.

SIGNIFICANCE

Results and insights are not only useful to understand basic neural mechanisms behind RI but are also valuable for general neural models of tinnitus.

Systematic review and meta-analysis of late auditory evoked potentials as a candidate biomarker in the assessment of tinnitus

Subjective tinnitus, the perception of sound in the absence of any sound source, is routinely assessed using questionnaires. The subjective nature of these tools hampers objective evaluation of tinnitus presence, severity and treatment effects. Late auditory evoked potentials (LAEPs) might be considered as a potential biomarker for assessing tinnitus complaints. Using a multivariate meta-analytic model including data from twenty-one studies, we determined the LAEP components differing systematically between tinnitus patients and controls. Results from this model indicate that amplitude of the P300 component is lower in tinnitus patients (standardized mean difference (SMD) = -0.83, p < 0.01), while latency of this component is abnormally prolonged in this population (SMD = 0.97, p < 0.01). No other investigated LAEP components were found to differ between tinnitus and non-tinnitus subjects. Additional sensitivity analyses regarding differences in experimental conditions confirmed the robustness of these results. Differences in age and hearing levels between the two experimental groups might have a considerable impact on LAEP outcomes and should be carefully considered in future studies. Although we established consistent differences in the P300 component between tinnitus patients and controls, we could not identify any evidence that this component might covary with tinnitus severity. We conclude that out of several commonly assessed LAEP components, only the P300 can be considered as a potential biomarker for subjective tinnitus, although more research is needed to determine its relationship with subjective tinnitus measures. Future trials investigating experimental tinnitus therapies should consider including P300 measurements in the evaluation of treatment effect.

Cortical Oscillatory Signatures Reveal the Prerequisites for Tinnitus Perception: A Comparison of Subjects With Sudden Sensorineural Hearing Loss With and Without Tinnitus

Just as the human brain works in a Bayesian manner to minimize uncertainty regarding external stimuli, a deafferented brain due to hearing loss attempts to obtain or "fill in" the missing auditory information, resulting in auditory phantom percepts (i.e., tinnitus). Among various types of hearing loss, sudden sensorineural hearing loss (SSNHL) has been extensively reported to be associated with tinnitus. However, the reason that tinnitus develops selectively in some patients with SSNHL remains elusive, which led us to hypothesize that patients with SSNHL with tinnitus (SSNHL-T) and those without tinnitus (SSNHL-NT) may exhibit different cortical activity patterns. In the current study, we compared resting-state quantitative electroencephalography findings between 13 SSNHL-T and 13 SSNHL-NT subjects strictly matched for demographic characteristics and hearing thresholds. By performing whole-brain source localization analysis complemented by functional connectivity analysis, we aimed to determine the as-yet-unidentified cortical oscillatory signatures that may reveal potential prerequisites for the perception of tinnitus in patients with SSNHL. Compared with the SSNHL-NT group, the SSNHL-T group showed significantly higher cortical activity in Bayesian inferential network areas such as the frontopolar cortex, orbitofrontal cortex (OFC), and pregenual anterior cingulate cortex (pgACC) for the beta 3 and gamma frequency bands. This suggests that tinnitus develops in a brain with sudden auditory deafferentation only if the Bayesian inferential network updates the missing auditory information and the pgACC-based top-down gatekeeper system is actively involved. Additionally, significantly increased connectivity between the OFC and precuneus for the gamma frequency band was observed in the SSNHL-T group, further suggesting that tinnitus derived from Bayesian inference may be linked to the default mode network so that tinnitus is regarded as normal. Taken together, our preliminary results suggest a possible mechanism for the selective development of tinnitus in patients with SSNHL. Also, these areas could serve as the potential targets of neuromodulatory approaches to preventing the development or prolonged perception of tinnitus in subjects with SSNHL.

Traffic noise exposure, cognitive decline, and amyloid-beta pathology in an AD mouse model

Concerns are growing that exposure to environmental pollutants, such as traffic noise, might cause cognitive impairments and predispose individuals toward the development of Alzheimer's disease (AD) dementia. In this study in a knock-in mouse model of AD, we investigated how chronic traffic noise exposure (CTNE) impacts cognitive performance and amyloid-beta (Aβ) pathology. A group of APP^{NL-G-F/NL-G-F} mice was exposed to CTNE (70 dB_A , 8 hr/day for 1 month) and compared with nonexposed counterparts. Following CTNE, an increase in hypothalamic-pituitary-adrenal (HPA) axis responsivity was observed by corticosterone assay of the blood. One month after CTNE, the CTNE group demonstrated impairments in cognitive and motor functions, and indications of anxiety-like behavior, relative to the control animals. The noise-exposed group also showed elevated Aβ aggregation, as inferred by a greater number of plaques and larger average plaque size in various regions of the brain, including regions involved in stress regulation. The results support that noise-associated dysregulation of the neuroendocrine system as a potential risk factor for developing cognitive impairment and Aβ pathology, which should be further investigated in human studies.

The state of the art of sound therapy for subjective tinnitus in adults

Background:

Sound therapy is a clinically common method of tinnitus management. Various forms of sound therapy have been developed, but there are controversies regarding the selection criteria and the efficacy of different forms of sound therapy in the clinic. Our goal was to review the types and forms of sound therapy and our understanding of how the different characteristics of tinnitus patients influence their curative effects so as to provide a reference for personalized choice of tinnitus sound therapy.

Method:

Using an established methodological framework, a search of six databases including PubMed identified 43 records that met our inclusion criteria. The search strategy used the following key words: tinnitus AND (acoustic OR sound OR music) AND (treatment OR therapy OR management OR intervention OR measure).

Results:

There are various forms of sound therapy, and most of them show positive therapeutic effects. The effect of customized sound therapy is generally better than that of non-customized sound therapy, and patients with more severe initial tinnitus respond better to sound therapy.

Conclusion:

Sound therapy can effectively suppress tinnitus, at least in some patients. However, there is a lack of randomized controlled trials to identify effective management strategies. Further studies are needed to identify the most effective form of sound therapy for individualized therapy, and large, multicenter, long-term follow-up studies are still needed in order to develop more effective and targeted sound-therapy protocols. In addition, it is necessary to analyze the characteristics of individual tinnitus patients and to unify the assessment criteria of tinnitus.

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.

Dorsomedial Prefrontal Cortex Repetitive Transcranial Magnetic Stimulation for Tinnitus: Promising Results of a Blinded, Randomized, Sham-Controlled Study

OBJECTIVES

Tinnitus is the perception of sound in ears or head without corresponding external stimulus. Despite the great amount of literature concerning tinnitus treatment, there are still no evidence-based established treatments for curing or for effectively reducing tinnitus intensity. Sham-controlled studies revealed beneficial effects using repetitive transcranial magnetic stimulation (rTMS). Still, results show moderate, temporary improvement and high individual variability. Subcallosal area (ventral and dorsomedial prefrontal and anterior cingulate cortices) has been implicated in tinnitus pathophysiology. Our objective is to evaluate the use of bilateral, high frequency, dorsomedial prefrontal cortex (DMPFC) rTMS in treatment of chronic subjective tinnitus.

DESIGN

Randomized placebo-controlled, single-blinded clinical trial. Twenty sessions of bilateral, 10 Hz rTMS at 120% of resting motor threshold of extensor hallucis longus were applied over the DMPFC. Fourteen patients underwent sham rTMS and 15 were submitted to active stimulation. Tinnitus Handicap Inventory (THI), visual analog scale, and tinnitus loudness matching were obtained at baseline and on follow-up visits. The impact of intervention on outcome measures was evaluated using mixed-effects restricted maximum likelihood regression model for longitudinal data.

RESULTS

A difference of 11.53 points in the THI score was found, favoring the intervention group (p = 0.05). The difference for tinnitus loudness matching was of 4.46 dB also favoring the intervention group (p = 0.09).

CONCLUSIONS

Tinnitus treatment with high frequency, bilateral, DMPFC rTMS was effective in reducing tinnitus severity measured by THI and matched tinnitus loudness when compared to sham stimulation.

Tinnitus Suppression Effect of Hearing Aids in Patients With High-frequency Hearing Loss: A Randomized Double-blind Controlled Trial

INTRODUCTION

Hearing aids (HAs) with frequency lowering have been used for high-frequency hearing loss (HFHL), but their effects on tinnitus relief have not been studied extensively. This randomized double-blind trial was performed to investigate and compare tinnitus suppression effects of conventional type HAs and frequency-lowering HAs in patients with HFHL.

METHODS

A total of 114 patients were randomized into three groups: conventional HA using wide dynamic range compression, HA with frequency translation, and HA with linear frequency transposition. Participants wore HAs for 3 months and then discontinued their use. The final evaluation was performed at 3 months after cessation of wearing HA (6 mo after the initial visit). The Tinnitus Handicap Inventory (THI) score and additional variables, such as matched tinnitus loudness and visual analog scale scores of subjectively perceived tinnitus loudness, daily awareness, and annoyance, were measured at the initial visit and at 3- and 6-month follow-ups.

RESULTS

THI score and most of the additional outcomes were significantly improved at 3 and 6 months (3 mo after HA removal) compared with their initial values in all three groups. The incidence rates of patients with improvements in the THI score by 20% or more were 71.0, 72.7, and 74.3% at 3 months, and 54.8, 51.6, and 59.4% at 6 months for the three groups, respectively. There were no significant differences in primary or additional variables between hearing aid types at either 3 or 6 months.

CONCLUSION

This is a consolidated standards of reporting trials-guided study providing direct evidence for tinnitus suppression effects of HA alone, without accompanying counseling or any other treatments, which lasted for at least 3 months after patients stopped using HAs. HAs effectively suppressed tinnitus in patients with HFHL regardless of the amplification strategy type.

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.

Global resting-state functional connectivity of neural oscillations in tinnitus with and without hearing loss

This study examined global resting-state functional connectivity of neural oscillations in individuals with chronic tinnitus and normal and impaired hearing. We tested the hypothesis that distinct neural oscillatory networks are engaged in tinnitus with and without hearing loss. In both tinnitus groups, with and without hearing loss, we identified multiple frequency band-dependent regions of increased and decreased global functional connectivity. We also found that the auditory domain of tinnitus severity, assayed by the Tinnitus Functional Index, was associated with global functional connectivity in both auditory and nonauditory regions. These findings provide candidate biomarkers to target and monitor treatments for tinnitus with and without hearing loss.

Assessing the Heterogeneity of Complaints Related to Tinnitus and Hyperacusis from an Unsupervised Machine Learning Approach: An Exploratory Study

Introduction: Subjective tinnitus (ST) and hyperacusis (HA) are common auditory symptoms that may become incapacitating in a subgroup of patients who thereby seek medical advice. Both conditions can result from many different mechanisms, and as a consequence, patients may report a vast repertoire of associated symptoms and comorbidities that can reduce dramatically the quality of life and even lead to suicide attempts in the most severe cases. The present exploratory study is aimed at investigating patients’ symptoms and complaints using an in-depth statistical analysis of patients’ natural narratives in a real-life environment in which, thanks to the anonymization of contributions and the peer-to-peer interaction, it is supposed that the wording used is totally free of any self-limitation and self-censorship. Methods: We applied a purely statistical, non-supervised machine learning approach to the analysis of patients’ verbatim exchanged on an Internet forum. After automated data extraction, the dataset has been preprocessed in order to make it suitable for statistical analysis. We used a variant of the Latent Dirichlet Allocation (LDA) algorithm to reveal clusters of symptoms and complaints of HA patients (topics). The probability of distribution of words within a topic uniquely characterizes it. The convergence of the log-likelihood of the LDA-model has been reached after 2,000 iterations. Several statistical parameters have been tested for topic modeling and word relevance factor within each topic. Results: Despite a rather small dataset, this exploratory study demonstrates that patients’ free speeches available on the Internet constitute a valuable material for machine learning and statistical analysis aimed at categorizing ST/HA complaints. The LDA model with K = 15 topics seems to be the most relevant in terms of relative weights and correlations with the capability to individualizing subgroups of patients displaying specific characteristics. The study of the relevance factor may be useful to unveil weak but important signals that are present in patients’ narratives. Discussion/Conclusion: We claim that the LDA non-supervised approach would permit to gain knowledge on the patterns of ST- and HA-related complaints and on patients’ centered domains of interest. The merits and limitations of the LDA algorithms are compared with other natural language processing methods and with more conventional methods of qualitative analysis of patients’ output. Future directions and research topics emerging from this innovative algorithmic analysis are proposed.

A 7 Tesla fMRI investigation of human tinnitus percept in cortical and subcortical auditory areas

Tinnitus is a clinical condition defined by hearing a sound in the absence of an objective source. Early experiments in animal models have suggested that tinnitus stems from an alteration of processing in the auditory system. However, translating these results to humans has proven challenging. One limiting factor has been the insufficient spatial resolution of non-invasive measurement techniques to investigate responses in subcortical auditory nuclei, like the inferior colliculus and the medial geniculate body (MGB). Here we employed ultra-high field functional magnetic resonance imaging (UHF-fMRI) at 7 Tesla to investigate the frequency-specific processing in sub-cortical and cortical regions in a cohort of six tinnitus patients and six hearing loss matched controls. We used task-based fMRI to perform tonotopic mapping and compared the magnitude and tuning of frequency-specific responses between the two groups. Additionally, we used resting-state fMRI to investigate the functional connectivity. Our results indicate frequency-unspecific reductions in the selectivity of frequency tuning that start at the level of the MGB and continue in the auditory cortex, as well as reduced thalamocortical and cortico-cortical connectivity with tinnitus. These findings suggest that tinnitus may be associated with reduced inhibition in the auditory pathway, potentially leading to increased neural noise and reduced functional connectivity. Moreover, these results indicate the relevance of high spatial resolution UHF-fMRI for the investigation of the role of sub-cortical auditory regions in tinnitus.

Amplitude Modulated Noise for Tinnitus Suppression in Tonal and Noise-Like Tinnitus

BACKGROUND

The phenomenon of short-term tinnitus suppression by different forms of acoustic stimulation is referred to as residual inhibition (RI). RI can be triggered in the majority of tinnitus cases and was found to be depending on the used intensity, length or types of sounds. Past research already stressed the impact of noise stimulation as well as the superiority of amplitude modulated (AM) pure tones at the individual tinnitus frequency for RI in tonal tinnitus. Recently a novel approach for the determination of noise-like tinnitus characteristics was proposed.

OBJECTIVES

The aim of the present study was to investigate whether in participants with noise-like tinnitus RI can be increased by AM noise stimuli according to the individual tinnitus frequency range.

METHODS

For this purpose the individual tinnitus characteristics (noise-like and tonal tinnitus) of 29 people affected by tinnitus (mean age = 55.59, 7 females, mean tinnitus duration = 159.97 months) were assessed via customizable noise-band matching. The objective was to generate bandpass filtered stimuli according to the individual tinnitus sound (individualized bandpass filtered [IBP] sounds). Subsequently, various stimuli differing in bandpass filtering and AM were tested with respect to their potential to induce RI. Participants were acoustically stimulated with 7 different types of stimuli for 3 min each and had to rate the loudness of their tinnitus after each stimuli.

RESULTS

Results indicate a general efficacy of noise stimuli for the temporary suppression of tinnitus, but no significant differences between AM and unmodulated IBP. Significantly better effects were observed for the subgroup with noise-like tinnitus (n = 14), especially directly after stimulation offset.

CONCLUSIONS

The study at hand provides further insights in potential mechanisms behind RI for different types of tinnitus. Beyond that, derived principles may qualify for new or extend current tinnitus sound therapies.

Maladaptive alterations of resting state cortical network in Tinnitus: A directed functional connectivity analysis of a larger MEG data set

The present study used resting state MEG whole-head recordings to identify how chronic tonal tinnitus relates to altered functional connectivity of brain's intrinsic cortical networks. Resting state MEG activity of 40 chronic tinnitus patients and 40 matched human controls was compared identifying significant alterations in intrinsic networks of the tinnitus population. Directed functional connectivity of the resting brain, at a whole cortex level, was estimated by means of a statistical comparison of the estimated phase Transfer Entropy (pTE) between the time-series of cortical activations, as reconstructed by LORETA. As pTE identifies the direction of the information flow, a detailed analysis of the connectivity differences between tinnitus patients and controls was possible. Results indicate that the group of tinnitus patients show increased connectivity from right dorsal prefrontal to right medial temporal areas. Our results go beyond previous findings by indicating that the role of the left para-hippocampal area is dictated by a modulation from dmPFC; a region that is part of the dorsal attention network (DAN), as well as implicated in the regulation of emotional processing. Additionally, this whole cortex analysis showed a crucial role of the left inferior parietal cortex, which modulated the activity of the right superior temporal gyrus, providing new hypotheses for the role of this area within the context of current tinnitus models. Overall, these maladaptive alterations of the structure of intrinsic cortical networks show a decrease in efficiency and small worldness of the resting state network of tinnitus patients, which is correlated to tinnitus distress.

RTMS parameters in tinnitus trials: a systematic review

Over the past few years extensive body of research was produced investigating the effects of repetitive transcranial magnetic stimulation (rTMS) for the treatment of chronic tinnitus with heterogeneous results. This heterogeneity is exemplified by two recently published large-scale clinical trials reporting different outcomes. Technical aspects of rTMS were suspected as a potential source for this incongruency. The aim of this systematic review is to examine the overall efficacy as well as to identify possible technical factors relevant for the effectiveness of rTMS tinnitus trials. Via a literature search appropriate original research papers were identified and rTMS parameters were extracted from each study arm for subsequent statistical analysis with respect to observed effects (significant vs. not significant pre-post rTMS effects). Our findings indicate that verum rTMS is superior to sham rTMS as demonstrated by the proportion of significant pre-post contrasts. Some relevant rTMS parameters (e.g., pulse waveform) are not reported. Lower rTMS stimulation intensity was associated with significant effects in verum rTMS arms. An additional stimulation of the DLPFC to the temporal cortex was not found to promote efficacy. Future research should consider differential effects of rTMS induced by technical parameters and strive for an exhaustive reporting of relevant rTMS parameters.

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

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

Association Between Subjective Tinnitus and Cervical Spine or Temporomandibular Disorders: A Systematic Review

Movements of the neck and jaw may modulate the loudness and pitch of tinnitus. The aim of the present study was to systematically analyze the strength of associations between subjective tinnitus, cervical spine disorders (CSD), and temporomandibular disorders (TMD). A systematic literature search of the Medline, Embase, and Pedro databases was carried out on articles published up to September 2017. This covered studies in which tinnitus and CSD or TMD were studied as a primary or a secondary outcome and in which outcomes were compared with a control group. Included articles were evaluated on nine methodological quality criteria. Associations between tinnitus and CSD or TMD were expressed as odds ratios. In total, 2,139 articles were identified, of which 24 studies met the inclusion criteria. Twice, two studies were based on the same data set; consequently, 22 studies were included in the meta-analysis. Methodological quality was generally limited by a lack of blinding, comparability of groups, and nonvalidated instruments for assessing CSD. Results indicated that patients with tinnitus more frequently reported CSD than subjects without tinnitus. The odds ratio was 2.6 (95% CI [1.1, 6.4]). For TMD, a bidirectional association with tinnitus was found; odds ratios ranged from 2.3 (95%CI [1.5, 3.6]) for arthrogenous TMD to 6.7 (95%CI [2.4, 18.8]) for unspecified TMD. Funnel plots suggested a publication bias. After adjusting for this, the odds ratios decreased, but associations persisted. There is weak evidence for an association between subjective tinnitus and CSD and a bidirectional association between tinnitus and TMD.

[Tinnitus: psychosomatic aspects]

Tinnitus is a common symptom of unclear origin that can be multifactorially caused and maintained. It is frequently, but not inevitably, associated with hearing loss. Emotional distress and maladaptive coping strategies - that are associated with or amplified by the tinnitus percept - pose key targets for psychological interventions. Once somatic contributors are identified and treated as applicable, psychological approaches comprise normalizing psychoeducational and psychotherapeutic interventions. Measures to improve hearing perception (e. g., hearing aids or cochlear implants) can also contribute to tinnitus habituation through direct (improvement of hearing perception) or indirect (improvement of emotional wellbeing or quality of life) effects.

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

Background

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

Objective

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

Methods

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

Results

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

Conclusions

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

International Registered Report Identifier (IRRID)

RR1-10.2196/12270

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.