Increased Frontal Response May Underlie Decreased Tinnitus Severity

Left prefrontal intermittent theta burst stimulation ameliorates tinnitus distress and symptoms of depression - A feasibility study

Tinnitus remains a notoriously difficult to treat clinical entity. 1-2% of the entire population report relevant emotional distress due to tinnitus, and causal treatments are lacking. Repetitive transcranial magnetic stimulation (rTMS), most commonly of auditory cortical areas, has shown mixed results in the past. Prefrontal rTMS, including intermittent theta burst stimulation (iTBS) has shown more promising results in the treatment of depression, and clinical data suggests a meaningful overlap between tinnitus and depression. Therefore, we performed a feasibility study of 28 consecutive patients with tinnitus treated with an iTBS protocol over the left dorsolateral prefrontal cortex for three weeks. After treatment, we observed significant ameliorations of tinnitus distress as measured by the Tinnitus Handicap Inventory Questionnaire (THI), the Tinnitus Functional Index (TFI), the Mini-Tinnitus Questionnaire (Mini-TQ) and also of depression as measured by the Major Depression Inventory (MDI). Effect sizes were small to moderate and short-lived. Treatment response rates, defined as improvement of the THI of at least 7 points, were 35.7%. At follow-up twelve weeks after end of treatment, severity of tinnitus and depression returned to approximately baseline level on a descriptive level. Amelioration of depressive symptoms correlated only with TFI change, but not that of other measures of tinnitus distress. The data suggest that a prefrontal iTBS protocol might be applied in the treatment of tinnitus and open avenues for future neurostimulatory treatments other than those of auditory regions.

Review and Perspective on Brain Bases of Tinnitus

In advancing our understanding of tinnitus, some of the more impactful contributions in the past two decades have come from human brain imaging studies, specifically the idea of both auditory and extra-auditory neural networks that mediate tinnitus. These networks subserve both the perception of tinnitus and the psychological reaction to chronic, continuous tinnitus. In this article, we review particular studies that report on the nodes and links of such neural networks and their inter-network connections. Innovative neuroimaging tools have contributed significantly to the increased understanding of anatomical and functional connections of attention, emotion-processing, and default mode networks in adults with tinnitus. We differentiate between the neural correlates of tinnitus and those of comorbid hearing loss; surprisingly, tinnitus and hearing loss when they co-occur are not necessarily additive in their impact and, in rare cases, additional tinnitus may act to mitigate the consequences of hearing loss alone on the brain. The scale of tinnitus severity also appears to have an impact on brain networks, with some of the alterations typically attributed to tinnitus reaching significance only in the case of bothersome tinnitus. As we learn more about comorbid conditions of tinnitus, such as depression, anxiety, hyperacusis, or even aging, their contributions to the network-level changes observed in tinnitus will need to be parsed out in a manner similar to what is currently being done for hearing loss or severity. Together, such studies advance our understanding of the heterogeneity of tinnitus and will lead to individualized treatment plans.

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.

Down-Regulation of Tinnitus Negative Valence via Concurrent HD-tDCS and PEI Technique: A Pilot Study

Around 30% of the general population experience subjective tinnitus, characterized by conscious attended awareness perception of sound without an external source. Clinical distress tinnitus is more than just experiencing a phantom sound, as it can be highly disruptive and debilitating, leading those affected to seek clinical help. Effective tinnitus treatments are crucial for psychological well-being, but our limited understanding of the underlying neural mechanisms and a lack of a universal cure necessitate further treatment development. In light of the neurofunctional tinnitus model predictions and transcranial electrical stimulation, we conducted an open-label, single-arm, pilot study that utilized high-definition transcranial direct current stimulation (HD-tDCS) concurrent with positive emotion induction (PEI) techniques for ten consecutive sessions to down-regulate tinnitus negative valence in patients with clinical distress tinnitus. We acquired resting-state functional magnetic resonance imaging scans of 12 tinnitus patients (7 females, mean age = 51.25 ± 12.90 years) before and after the intervention to examine resting-state functional connectivity (rsFC) alterations in specific seed regions. The results showed reduced rsFC at post-intervention between the attention and emotion processing regions as follows: (1) bilateral amygdala and left superior parietal lobule (SPL), (2) left amygdala and right SPL, (3) bilateral dorsolateral prefrontal cortex (dlPFC) and bilateral pregenual anterior cingulate cortex (pgACC), and (4) left dlPFC and bilateral pgACC (FWE corrected p < 0.05). Furthermore, the post-intervention tinnitus handicap inventory scores were significantly lower than the pre-intervention scores (p < 0.05). We concluded that concurrent HD-tDCS and PEI might be effective in reducing tinnitus negative valence, thus alleviating tinnitus distress.

Disruptions of default mode network and precuneus connectivity associated with cognitive dysfunctions in tinnitus

Tinnitus is the perception of a ringing, buzzing or hissing sound "in the ear" without external stimulation. Previous research has demonstrated changes in resting-state functional connectivity in tinnitus, but findings do not overlap and are even contradictory. Furthermore, how altered functional connectivity in tinnitus is related to cognitive abilities is currently unknown. Here we investigated resting-state functional connectivity differences between 20 patients with chronic tinnitus and 20 control participants matched in age, sex and hearing loss. All participants underwent functional magnetic resonance imaging, audiometric and cognitive assessments, and filled in questionnaires targeting anxiety and depression. Significant differences in functional connectivity between tinnitus patients and control participants were not obtained. However, we did find significant associations between cognitive scores and functional coupling of the default mode network and the precuneus with the superior parietal lobule, supramarginal gyrus, and orbitofrontal cortex. Further, tinnitus distress correlated with connectivity between the precuneus and the lateral occipital complex. This is the first study providing evidence for disruptions of default mode network and precuneus coupling that are related to cognitive dysfunctions in tinnitus. The constant attempt to decrease the tinnitus sensation might occupy certain brain resources otherwise available for concurrent cognitive operations.

The effects of dietary and physical activity interventions on tinnitus symptoms: An RCT

OBJECTIVE

Subjective tinnitus is defined as the perception of irregular sound at different frequencies. Although the underlying cause of tinnitus is unclear, increased body weight is known to increase tinnitus symptoms. The present study aimed to determine the effects of dietary and physical activity interventions on tinnitus symptoms.

METHODS

Sixty-three obese subjects with tinnitus aged 20 to 65 years were divided into diet + physical activity (P.A.) (n = 15), diet (n = 16), P.A. (n = 15), and control (n = 17) groups. Dietary records, anthropometric measurements, Tinnitus Handicap Inventory (THI), Beck Depression Inventory (BDI), Short-Form Health Survey (SF-36), and Visual Analogue Scale (VAS) of all individuals were recorded and compared at the baseline and at study completion.

RESULTS

Body weight decreased in the diet + P.A. (-5.9 (3.5) kg), diet (-3.4 (0.9) kg), and P.A. (-2.0 (2.1) kg) groups compared to the baseline (p < 0.05). There was a more significant decrease in tinnitus frequency, tinnitus severity, and VAS scores in individuals with a weight loss of ≥ 5.0% than in those with < 5.0% (p < 0.05). A decrease of 1 kg/m² in BMI decreased the BDI score by 0.485 units and the THI score by 0.523 units. Step counts were increased in the diet + P.A. (3562.3±739.9) and P.A. (3797.1 ± 1801.1) groups compared to baseline (p < 0.01). Each increase of 1000 steps increased the SF-36 score by 1.592 units and decreased the THI score by 0.750 units (p < 0.05).

CONCLUSION

Dietary and physical activity interventions, alone or in combination, alleviated tinnitus symptoms and increased quality of life in individuals with tinnitus. Due to its contribution to obesity prevention and positive effects on tinnitus, organizing dietary and physical activity programs for obese individuals with tinnitus would improve these individuals' quality of life.

Self-Directed Neurofeedback Treatment for Subjective Tinnitus Patients Evaluated by Multimodal Functional Imaging

Neurofeedback (NFB) is a relatively novel approach to the treatment of tinnitus, and prior studies have demonstrated that the increases in alpha activity rather than reduced delta power seem to drive these NFB-related improvements in tinnitus symptoms. The present study was therefore designed to explore whether the implementation of an alpha training protocol with a portable neurofeedback apparatus would achieve improvements in tinnitus patient symptoms. In this study, 38 tinnitus patients underwent NFB training while 18 were enrolled in a control group. The study was single-blinded such that only participants were not aware of their group assignments. Those in the NFB group underwent 15 NFB training sessions over 5 weeks, in addition to pre- and posttraining tests including the Tinnitus Handicap Inventory (THI), Tinnitus Handicap Questionnaire (THQ), visual analog scales (VAS), electroencephalography (EEG), and functional magnetic resonance imaging (fMRI). Our result find that when the THI, THQ, and VAS scores of patients in the two groups were assessed after a 5-week training period, these scores were unchanged in control patients whereas they had significantly improved in the NFB group patients. EEG analyses revealed that the alpha band was increased in the occipital lobe following NFB treatment, while fMRI indicated an increase in regional homogeneity (ReHo) in the right frontal lobe of patients in the NFB group after treatment that was negatively correlated with THI and VAS scores. The results of this analysis indicate that alpha NFB training can be effectively used to reduce tinnitus-related distress and sound perception in patients.

Evaluating the Efficacy of a Smartphone App for Tinnitus Relief Using Behavioral and Brain Imaging Measures

PURPOSE

In this exploratory, open-label study, we used behavioral and brain imaging measures to assess the effectiveness of a smartphone application (ReSound Relief app), which aims to help reduce tinnitus-related distress.

METHOD

Fourteen participants with a wide range of tinnitus-related symptoms and who were not currently undergoing any external treatment participated. They completed the 6-month study and reported different levels of engagement with the app.

RESULTS

Across a range of tinnitus questionnaires, most participants showed either no change or decrease in tinnitus handicap. Resting-state and task-based functional magnetic resonance imaging (fMRI) data were collected at baseline and the end of the study. Resting-state fMRI of 12 participants revealed alterations in interregional connectivity of default mode, salience, emotion, auditory, and visual processing networks at the end of the intervention period compared to baseline. Ratings of affective sounds (as pleasant, neutral, or unpleasant) were assessed using fMRI, and comparison after 6 months of app usage revealed reduced activity in the left superior temporal gyrus (secondary auditory cortex), right superior occipital gyrus, and left posterior cingulate cortex. Our findings were not significant at a false discovery rate level of p < .05.

CONCLUSIONS

The reported changes were not significant, possibly due to the small sample size, heterogeneity of the tinnitus handicap among subjects at the start of the project, and the length of the intervention period. Nevertheless, this study underscores the ease of usage of the app and the potential use of brain imaging to assess changes due to a passive, self-administered intervention for individuals with varying levels of tinnitus severity.

Pros and cons in tinnitus brain: Enhancement of global connectivity for alpha and delta waves

Interactions among cortical areas of tinnitus brain remained unclear. Weaker alpha and stronger delta activities in tinnitus have been noted over auditory cortices. However, the interplay between a single substrate with whole brain within alpha/delta band remained unknown. Thirty-one patients with chronic tinnitus were recruited. Thirty-four healthy volunteers served as controls. Magnetoencephalographic measurements of spontaneous activities were performed. The strength of alpha/delta activities was analyzed. By dividing cortices into 38 regions of interest (ROIs), measurements of connectivity were performed using amplitude envelope correlation (AEC). Global connectivity was calculated by adding and averaging connectivity of single ROI with every other region. There were no significant differences in mean power of alpha and delta band between groups, despite the trend of stronger alpha and weaker delta band in controls. The global connectivity of alpha wave was significantly stronger in tinnitus for left frontal pole, and of delta wave for bilateral pars orbitalis, bilateral superior temporal, bilateral middle temporal, right pars triangularis, right transverse temporal, right inferior temporal, and right supra-marginal. The global connectivity of alpha/delta waves was enhanced for tinnitus in designated ROIs of frontal/temporal/parietal lobes. The underlying mechanism(s) might be associated with augmentation/modulation of tinnitus perception. Our results corroborated the evolving consensus about neural correlates inside frontal/temporal/parietal lobes as essential elements of hubs for central processing of tinnitus. Further study to explore the resolution of effective connectivity between those ROIs and respective substrates by using AEC will be necessary for the evaluation of pathogenetic scenario for 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.

Hear me out: rethinking internal auditory meatus magnetic resonance imaging in primary care. A cohort evaluation

Background

Imaging detects acoustic neuroma, a rare pathology associated with asymmetric sensorineural hearing loss and tinnitus, that is mostly managed conservatively. Scanning indication is debatable, without evaluation in primary care, despite the high burden of audiovestibular symptoms and commissioning of general practitioner imaging.

Method

Cohort evaluation of two years' internal auditory meatus magnetic resonance imaging in primary care.

Results

Of 200 scans requested by 77 general practitioners, only 33 per cent conformed to guideline indications. Most were referred to specialists, regardless of result. Only 10.5 per cent were appropriately imaged to rule out neuroma without specialist referral. One neuroma was detected (diagnostic yield 0.5 per cent) in a patient already referred. Incidental findings were shown in 44.5 per cent, triggering low-value cascades in 18 per cent. Whilst fewer than 1 in a 1000 imaged patients may improve through surgery, 1 in 5 can suffer negative imaging cascades.

Conclusion

Considering the bi-directional relationship between distress and audio-vestibular symptoms, anxiety-provoking imaging overuse should be minimised. In low-prevalence primary care, retrocochlear imaging could be limited to those with asymmetric sensorineural hearing loss. Alternatively, assessment and imaging could be shifted to audiologist-led settings, with a wider therapeutic offer, likely more beneficial and cost-effective than conventional surgical pathways.

An Albanian translation of a questionnaire for self-reported tinnitus assessment

OBJECTIVE

To our knowledge, there is no published study investigating the characteristics of people experiencing tinnitus in Albania. Such a study would be important, providing the basis for further research in this region and contributing to a wider understanding of tinnitus heterogeneity across different geographic locations. The main objective of this study was to develop an Albanian translation of a standardised questionnaire for tinnitus research, namely the European School for Interdisciplinary Tinnitus Research-Screening Questionnaire (ESIT-SQ). A secondary objective was to assess its applicability and usefulness by conducting an exploratory survey on a small sample of the Albanian tinnitus population.

DESIGN AND STUDY SAMPLE

Three translators were recruited to create the Albanian ESIT-SQ translation following good practice guidelines. Using this questionnaire, data from 107 patients attending otolaryngology clinics in Albania were collected.

RESULTS

Participants reporting various degrees of tinnitus symptom severity had distinct phenotypic characteristics. Application of a random forest approach on this preliminary dataset showed that self-reported hearing difficulty, and tinnitus duration, pitch and temporal manifestation were important variables for predicting tinnitus symptom severity.

CONCLUSIONS

Our study provided an Albanian translation of the ESIT-SQ and demonstrated that it is a useful tool for tinnitus profiling and subgrouping.

Salience, emotion, and attention: The neural networks underlying tinnitus distress revealed using music and rest

In the present study, we used an innovative music-rest interleaved fMRI paradigm to investigate the neural correlates of tinnitus distress. Tinnitus is a poorly-understood hearing disorder where individuals perceive sounds, in the absence of an external source. Although the great majority of individuals habituate to chronic tinnitus and report few symptoms, a minority report debilitating distress and annoyance. Prior research suggests that a diverse set of brain regions, including the attention, the salience, and the limbic networks, play key roles in mediating both the perception of tinnitus and its impact on the individual; however, evidence of the degree and extent of their involvement has been inconsistent. Here, we minimally modified the conventional resting state fMRI by interleaving it with segments of jazz music. We found that the functional connectivity between a set of brain regions-including cerebellum, precuneus, superior/middle frontal gyrus, and primary visual cortex-and seeds in the dorsal attention network, the salience network, and the amygdala, were effective in fractionating the tinnitus patients into two subgroups, characterized by the severity of tinnitus-related distress. Further, our findings revealed cross-modal modulation of the attention and salience networks by the visual modality during the music segments. On average, the more bothersome the reported tinnitus, the stronger was the exhibited inter-network functional connectivity. This study substantiates the essential role of the attention, salience, and limbic networks in tinnitus habituation, and suggests modulation of the attention and salience networks across the auditory and visual modalities as a possible compensatory mechanism for bothersome tinnitus.

Decreased resting perfusion in precuneus and posterior cingulate cortex predicts tinnitus severity

Functional magnetic resonance imaging has been increasingly used to understand the mechanisms involved in subjective tinnitus; however, researchers have struggled to reach a consensus about a primary mechanistic model to explain tinnitus. While many studies have used functional connectivity of the BOLD signal to understand how patterns of activity change with tinnitus severity, there is much less research on whether there are differences in more fundamental physiology, including cerebral blood flow, which may help inform the BOLD measures. Here, arterial spin labeling was used to measure perfusion in four regions-of-interest, guided by current models of tinnitus, in a sample of 60 tinnitus patients and 31 control subjects. We found global reductions in cerebral perfusion in tinnitus compared with controls. Additionally, we observed a significant negative correlation between tinnitus severity and perfusion. These results demonstrate that examining perfusion from the whole brain may present a complementary tool for studying tinnitus. More research will help better understand the physiology underlying these differences in perfusion.

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Global cerebral blood flow is reduced in tinnitus.

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Tinnitus severity is negatively correlated with cerebral blood flow globally.

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Tinnitus severity is negatively correlated with cerebral blood flow in the precuneus and posterior cingulate cortex.

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Hearing loss predicted reduced cerebral blood flow in the precuneus in participants without tinnitus.

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The presence or absence of hearing loss did not affect the correlation between tinnitus severity and cerebral blood flow.

A Review and a Framework of Variables for Defining and Characterizing Tinnitus Subphenotypes

Tinnitus patients can present with various characteristics, such as those related to the tinnitus perception, symptom severity, and pattern of comorbidities. It is speculated that this phenotypic heterogeneity is associated with differences in the underlying pathophysiology and personal reaction to the condition. However, there is as yet no established protocol for tinnitus profiling or subtyping, hindering progress in treatment development. This review summarizes data on variables that have been used in studies investigating phenotypic differences in subgroups of tinnitus, including variables used to both define and compare subgroups. A PubMed search led to the identification of 64 eligible articles. In most studies, variables for subgrouping were chosen by the researchers (hypothesis-driven approach). Other approaches included application of unsupervised machine-learning techniques for the definition of subgroups (data-driven), and subgroup definition based on the response to a tinnitus treatment (treatment response). A framework of 94 variable concepts was created to summarize variables used across all studies. Frequency statistics for the use of each variable concept are presented, demonstrating those most and least commonly assessed. This review highlights the high dimensionality of tinnitus heterogeneity. The framework of variables can contribute to the design of future studies, helping to decide on tinnitus assessment and subgrouping.

Effects of Chronic Tinnitus on Metabolic and Structural Changes in Subjects With Mild Cognitive Impairment

Tinnitus is a conscious auditory perception in the absence of an external stimulus. Despite previous reports of a recognized association between tinnitus and cognitive deficits, the effects of tinnitus on functional and structural brain changes associated with cognitive deficits remain unknown. We aimed to investigate the changes in glucose metabolism and gray matter (GM) volume in subjects diagnosed with mild cognitive impairment (MCI) depending on tinnitus. Twenty-three subjects were subclassified into MCI with the chronic tinnitus (MCI_T) and MCI without tinnitus (MCI_NT) groups. Encouraged by the identification of neural substrates associated with tinnitus and cognitive deficits, we correlated the extent of tinnitus severity with the changes in glucose metabolism and GM volume and conducted a glucose metabolic connectivity study. Compared to the MCI_NT group, the MCI_T group showed significantly lower metabolism in the right superior temporal pole and left fusiform gyrus. Additionally, the GM volume in the right insula was markedly lower in the MCI_T group compared to the MCI_NT group. Moreover, correlation analyses in metabolism or GM volumes revealed specific brain regions associated with the cognitive decline with increasing tinnitus severity. Metabolic connectivity analysis revealed that MCI_NT had markedly strengthened intra-hemispheric connectivity in the frontal, parietal, and occipital regions than did MCI_T. Furthermore, MCI_NT showed a strong negative association between the parietal and temporal and parietal and limbic regions, but the association was not observed in MCI_T. These findings indicate that tinnitus may cause metabolic and structural changes in the brain and alters complex inter- or intra-hemispheric networks in MCI. Considering the impact of MCI on accelerating dementia, these results provide a valuable basis on which yet-to-be-identified neurodegenerative markers of tinnitus can be refined.

Tinnitus impairs segregation of competing speech in normal-hearing listeners

Many tinnitus patients report difficulties understanding speech in noise or competing talkers, despite having "normal" hearing in terms of audiometric thresholds. The interference caused by tinnitus is more likely central in origin. Release from informational masking (more central in origin) produced by competing speech may further illuminate central interference due to tinnitus. In the present study, masked speech understanding was measured in normal hearing listeners with or without tinnitus. Speech recognition thresholds were measured for target speech in the presence of multi-talker babble or competing speech. For competing speech, speech recognition thresholds were measured for different cue conditions (i.e., with and without target-masker sex differences and/or with and without spatial cues). The present data suggest that tinnitus negatively affected masked speech recognition even in individuals with no measurable hearing loss. Tinnitus severity appeared to especially limit listeners' ability to segregate competing speech using talker sex differences. The data suggest that increased informational masking via lexical interference may tax tinnitus patients' central auditory processing resources.

Electrophysiological correlates of focused attention on low- and high-distressed tinnitus

OBJECTIVES

The study aimed at determining the EEG correlates of concentration on either low or high-distressed tinnitus.

METHODS

Sixty-seven patients (36 women, mean age = 50.34 ± 12.94 years) with chronic tinnitus were assigned to either a high (HD) or low (LD) tinnitus-related distress group based on THI results. All participants took part in the EEG study comprising two 3-4 min blocks of focusing on either tinnitus (Tinnitus Focus Condition, TFC) or the sensations from one's own body (Body Focus Condition, BFC). The absolute power and current density of 8 frequency bands in 7 clusters were compared between conditions and groups.

RESULTS

The most pronounced differences were found in the HD patients in the TFC, relative to the BFC, i.e. reduced power of frontally distributed low alpha (8-10 Hz) and posterior high alpha (10-12 Hz) as well as lower current density of 8-10 Hz rhythm over the right frontal/anterior cingulate cortex and higher middle beta (15-18 Hz) density in the precuneus. The HD, relative to LD patients, in both conditions, exhibited increased low beta (12-15 Hz) power over the left middle area and greater higher beta (15-25 Hz) power in the left posterior region.

CONCLUSIONS

The present study contrasted bioelectrical activity, acquired when concentrating on tinnitus with EEG data collected whilst patients focused on their body. Decreased alpha power and current density in the frontal/cingulate cortex when listening to bothersome tinnitus might reflect greater cortical arousal whereas increased beta power and density in the precuneus/posterior cingulate activity in this condition could be indicative for elevated tension or augmented cognitive/emotional processing of tinnitus sound. Enhanced beta rhythm in patients with high versus low tinnitus distress, observed independently of the study condition, may be due to greater self-focused attention or more active processing of sensations derived from the own body.

Chronic tinnitus and the limbic system: Reappraising brain structural effects of distress and affective symptoms

Chronic tinnitus has been associated with brain structural changes in both the auditory system as well as limbic system. While there is considerable inconsistency across brain structural findings, growing evidence suggests that distress and other non-auditory symptoms modulate effects. In this study we addressed this issue, testing the hypothesis that limbic changes in tinnitus relate to both disease-related distress as well as co-morbid psychopathology. We obtained high-resolution structural magnetic resonance imaging (MRI) scans from a total of 125 subjects: 59 patients with bilateral chronic tinnitus (29 with a co-morbid psychiatric condition, 30 without), 40 healthy controls and 26 psychiatric controls with depression/anxiety disorders (without tinnitus). Voxel-based morphometry with the CAT12 software package was used to analyse data. First, we analysed data based on a 2 × 2 factorial design (tinnitus; psychiatric co-morbidity), showing trend-level effects for tinnitus in ROI analyses of the anterior cingulate cortex and superior/transverse temporal gyri, and for voxel-based analysis in the left parahippocampal cortex. Multiple regression analyses showed that the parahippocampal finding was mostly predicted by tinnitus rather than (dimensional) psychopathology ratings. Comparing only low-distress tinnitus patients (independent of co-morbid conditions) with healthy controls also showed reduced left parahippocampal grey matter. Our findings demonstrate that depression and anxiety (not only subjective distress) are major modulators of brain structural effects in tinnitus, calling for a stronger consideration of psychopathology in future neurobiological and clinical studies of tinnitus.

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Chronic tinnitus is associated with high psychiatric co-morbidity and distress.

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Parahippocamal grey matter is associated with tinnitus rather than distress.

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Psychiatric co-morbidity modulates tinnitus-related structural patterns.

Functional Brain Changes During Mindfulness-Based Cognitive Therapy Associated With Tinnitus Severity

Mindfulness-based therapies have been introduced as a treatment option to reduce the psychological severity of tinnitus, a currently incurable chronic condition. This pilot study of twelve subjects with chronic tinnitus investigates the relationship between measures of both task-based and resting state functional magnetic resonance imaging (fMRI) and measures of tinnitus severity, assessed with the Tinnitus Functional Index (TFI). MRI was measured at three time points: before, after, and at follow-up of an 8-week long mindfulness-based cognitive therapy intervention. During the task-based fMRI with affective sounds, no significant changes were observed between sessions, nor was the activation to emotionally salient compared to neutral stimuli significantly predictive of TFI. Significant results were found using resting state fMRI. There were significant decreases in functional connectivity among the default mode network, cingulo-opercular network, and amygdala across the intervention, but no differences were seen in connectivity with seeds in the dorsal attention network (DAN) or fronto-parietal network and the rest of the brain. Further, only resting state connectivity between the brain and the amygdala, DAN, and fronto-parietal network significantly predicted TFI. These results point to a mostly differentiated landscape of functional brain measures related to tinnitus severity on one hand and mindfulness-based therapy on the other. However, overlapping results of decreased amygdala connectivity with parietal areas and the negative correlation between amygdala-parietal connectivity and TFI is suggestive of a brain imaging marker of successful treatment.

Replicability of Neural and Behavioral Measures of Tinnitus Handicap in Civilian and Military Populations: Preliminary Results

Purpose In the past decade, resting-state functional connectivity, acquired using functional magnetic resonance imaging (fMRI), has emerged as a popular measure of tinnitus, especially as related to self-reported handicap or psychological reaction. The goal of this study was to assess replicability of neural correlates of tinnitus, namely, resting-state functional connectivity, in the same individuals acquired over 2 sessions. Method Data were collected at 2 different sites (University of Illinois at Urbana-Champaign and Joint Base San Antonio Wilford Hall Ambulatory Surgical Center) using similar 3T magnets and similar data acquisition paradigms. Thirty-six patients (all civilians) were scanned using resting-state fMRI at the University of Illinois at Urbana-Champaign. Ten patients, active-duty Service members and Veterans, were scanned at the Wilford Hall Ambulatory Surgical Center and the Department of Defense Hearing Center of Excellence. Each participant was scanned twice, a week apart, using identical protocols of 10 min resting-state fMRI. Results Tinnitus handicap scores using the Tinnitus Functional Index and the Tinnitus Primary Function Questionnaire ranged between no or mild handicap to moderately severe handicap but did not significantly differ between visits. We examined the default mode, dorsal attention, and auditory resting-state networks and found that the strength of the within-network functional connections across visit was similar for the attention and default mode networks but not for the auditory network. In addition, the functional connection between the attention network and precuneus, a region of the default mode network, was also replicable across visits. Conclusions Our results show that resting-state fMRI measures are replicable and reliable in patients with a subjective condition, although some networks and functional connections may be more stable than others. This paves the way for using resting-state fMRI to measure the efficacy of tinnitus interventions and as a tool to help propose better management options.

The Role of Cognitive Control in Tinnitus and Its Relation to Speech-in-Noise Performance

Self-reported difficulties in speech-in-noise (SiN) recognition are common among tinnitus patients. Whereas hearing impairment that usually co-occurs with tinnitus can explain such difficulties, recent studies suggest that tinnitus patients with normal hearing sensitivity still show decreased SiN understanding, indicating that SiN difficulties cannot be solely attributed to changes in hearing sensitivity. In fact, cognitive control, which refers to a variety of top-down processes that human beings use to complete their daily tasks, has been shown to be critical for SiN recognition, as well as the key to understand cognitive inefficiencies caused by tinnitus. In this article, we review studies investigating the association between tinnitus and cognitive control using behavioral and brain imaging assessments, as well as those examining the effect of tinnitus on SiN recognition. In addition, three factors that can affect cognitive control in tinnitus patients, including hearing sensitivity, age, and severity of tinnitus, are discussed to elucidate the association among tinnitus, cognitive control, and SiN recognition. Although a possible central or cognitive involvement has always been postulated in the observed SiN impairments in tinnitus patients, there is as yet no direct evidence to underpin this assumption, as few studies have addressed both SiN performance and cognitive control in one tinnitus cohort. Future studies should aim at incorporating SiN tests with various subjective and objective methods that evaluate cognitive performance to better understand the relationship between SiN difficulties and cognitive control in tinnitus patients.

Dissociating tinnitus patients from healthy controls using resting-state cyclicity analysis and clustering

Chronic tinnitus is a common and sometimes debilitating condition that lacks scientific consensus on physiological models of how the condition arises as well as any known cure. In this study, we applied a novel cyclicity analysis, which studies patterns of leader-follower relationships between two signals, to resting-state functional magnetic resonance imaging (rs-fMRI) data of brain regions acquired from subjects with and without tinnitus. Using the output from the cyclicity analysis, we were able to differentiate between these two groups with 58–67% accuracy by using a partial least squares discriminant analysis. Stability testing yielded a 70% classification accuracy for identifying individual subjects’ data across sessions 1 week apart. Additional analysis revealed that the pairs of brain regions that contributed most to the dissociation between tinnitus and controls were those connected to the amygdala. In the controls, there were consistent temporal patterns across frontal, parietal, and limbic regions and amygdalar activity, whereas in tinnitus subjects, this pattern was much more variable. Our findings demonstrate a proof-of-principle for the use of cyclicity analysis of rs-fMRI data to better understand functional brain connectivity and to use it as a tool for the differentiation of patients and controls who may differ on specific traits.

Chronic tinnitus is a common, yet poorly understood, condition without a known cure. Understanding differences in the functioning of brains of tinnitus patients and controls may lead to better knowledge regarding the physiology of the condition and to subsequent treatments. There are many ways to characterize relationships between neural activity in different parts of the brain. Here, we apply a novel method, called cyclicity analysis, to functional MRI data obtained from tinnitus patients and controls over a period of wakeful rest. Cyclicity analysis lends itself to interpretation as analysis of temporal orderings between elements of time-series data; it is distinct from methods like periodicity analysis or time correlation analysis in that its theoretical underpinnings are invariant to changes in time scales of the generative process. In this proof-of-concept study, we use the feature generated from the cyclicity analysis of the fMRI data to investigate group level differences between tinnitus patients and controls. Our findings indicate that temporal ordering of regional brain activation is much more consistent in the control population than in tinnitus population. We also apply methods of classification from machine learning to differentiate between the two populations with moderate amount of success.

MRI Verification of a 10-20 Targeting Protocol Used During Transcranial Magnetic Stimulation Sessions for Tinnitus

Langguth et al. (2006) described a method for targeting primary auditory cortex (PAC) during transcranial magnetic stimulation (TMS) using the 10–20 electroencephalography system. Study aims were to measure the degree of accuracy in placing the TMS coil on the scalp overlying PAC using the 10–20 method and determine the extent to which accuracy depends on the hemisphere of the coil placement. Twelve participants underwent anatomical magnetic resonance imaging (MRI) of their head in a 3T scanner. Before imaging, a fiducial marker was placed on their scalp corresponding to the TMS coil position. MRI scans were analyzed to determine the distance from the fiducial marker to PAC for each participant. On average, the 10–20 method resulted in distances in the medial–lateral, anterior-posterior, and inferior-superior dimensions that were within a few millimeters (~ 4 mm) of each other between the left and right hemispheres. The fiducial marker was, on average, 10.4 mm superior and 10.8 mm posterior to the optimal scalp location that minimized the distance to PAC. Individual asymmetries and other systematic differences found in this study raise important considerations to keep in mind that might necessitate using an MRI-guided method of coil-positioning when targeting PAC for TMS.