Tinnitus and underlying brain mechanisms

Bidirectional Associations Between Tinnitus Subtypes and Psychiatric Conditions

OBJECTIVE

To evaluate the temporal and bidirectional relationships between tinnitus subtypes-pulsatile tinnitus (PT) and non-pulsatile tinnitus (NPT)-and psychiatric conditions, specifically generalized anxiety disorder (GAD) and major depression (MD).

METHODS

This retrospective cohort study utilized data from the TriNetX Research Network, including over 140 million patients. Patients were categorized based on ICD-10 codes for PT, NPT, GAD, and MD. Propensity score matching (PSM) was applied to control for demographic and clinical confounders. Statistical analyses included chi-square tests, odds ratios (OR) with 95% confidence intervals (CIs) to ascertain the statistical significance of temporal associations between tinnitus subtypes and psychiatric conditions.

RESULTS

NPT patients had significantly higher risks of developing GAD and MD than PT patients. PSM analyses confirmed that PT patients had consistently lower risks of developing these conditions, even across treated and untreated subgroups. Among patients with tinnitus, those with PT had significantly higher rates of pre-existing GAD and MD compared to those with NPT.

CONCLUSION

NPT is associated with significantly higher risks of developing GAD and MD compared to PT, highlighting a greater psychiatric burden among this subgroup. Conversely, patients with tinnitus who had pre-existing GAD or MD were more likely to have PT than NPT, suggesting a bidirectional relationship. These findings underscore the importance of integrating mental health assessment into tinnitus care and inform future research into subtype-specific management strategies.

LEVEL OF EVIDENCE: 3

Fasting Glucose, Haemoglobin A1C (HbA1c), Blood Lipid, and Triglyceride-Glucose Index Parameters in Relation to Subjective Tinnitus

Objectives: This study aimed to analyse blood glucose and lipid levels in subjective tinnitus compared to healthy controls. Method: A total of 414 patients with subjective tinnitus and 274 healthy participants were enrolled. All participants underwent comprehensive laboratory testing, which included measurements of fasting blood glucose, HbA1c, and blood lipids. Results: The tinnitus group had significantly higher glucose levels than the control group (p = 0.024). Additionally, the HbA1c levels were higher in the tinnitus group (p = 0.006). Tinnitus patients exhibited elevated levels of total cholesterol (p < 0.001), triglycerides (p < 0.001), and LDL (p < 0.001). However, HDL levels showed no significant difference (p = 0.984). Although the triglyceride-glucose index tends to show higher values in the tinnitus group, this difference is statistically insignificant (p = 0.688). ROC indicated that LDL had the highest sensitivity for predicting tinnitus (AUC = 0.620; p < 0.001, 95% CI: 0.573-0.668). Other parameters showed significant results, excluding the triglyceride-glucose index (AUC = 0.514; p = 0.688, 95% CI: 0.443-0.585), which was not a significant predictor. Glucose levels significantly correlate with age (rho = 0.338, p < 0.001) and tinnitus onset (rho = 0.107, p = 0.034). Additionally, age showed a significant correlation with total cholesterol levels (rho = 0.156, p = 0.002) and triglycerides (rho = 0.121, p = 0.020) and tinnitus onset (rho = 0.344, p < 0.001). Logistic regression analysis revealed that the presence of tinnitus was significantly associated with elevated HbA1c levels (p = 0.007) and TG levels (p = 0.001). Furthermore, the occurrence of chronic tinnitus was significantly influenced by elevated glucose levels (p = 0.026). Conclusions: The results showed increased glucose and blood lipid levels in tinnitus. LDL levels exhibited the highest sensitivity in predicting tinnitus. However, the TyG index was not a significant predictor. Given the cross-sectional design of the study, which may limit the results, further longitudinal studies are necessary.

Exploring P300 Responses in Tinnitus: Linking Cognitive and Audiological Assessments

Aim

The study aimed to evaluate the effect of tinnitus masking on cognitive functioning and the efficacy of tinnitus retraining therapy in reducing the severity of tinnitus handicap.

Method

The study recruited 15 subjects (mean age = 47.1 ± 11.5) with unilateral chronic tinnitus (6 participants with right-ear tinnitus and 9 participants with left-ear tinnitus); and mild to moderate sensorineural hearing loss. Conducted in two phases, Phase 1 comprised case history, audiometric testing, tinnitus matching, and THI-Bangla assessment. Phase 2 involved P300 administration followed by a 60-session tinnitus retraining therapy (online-offline modality), concluding with post-therapy P300 and THI-Bangla assessments. Therapy outcomes were evaluated by improvements in P300 latency and amplitude and THI-Bangla scores.

Results

A significant improvement observed post-therapy, with reductions in mean P300 latency for both left (p < 0.001) and right (p < 0.001) ears. Mean P300 amplitude also increased significantly post-therapy for left (p < 0.001) and right (p < 0.001) ears. THI scores also declined substantially (p < 0.001), with a post-therapy mean THI score of 17.80 (SD = 4.64) for males and 12.20 (SD = 3.42) for females, revealing a significant difference (p = 0.033).

Conclusion

These findings support the efficacy of tinnitus retraining therapy in reducing tinnitus related distress and enhancing cognitive processing, as evidenced by P300 improvements.

Tinnitus prevalence and associations with leisure noise exposure among Canadians, aged 6 to 79 years

OBJECTIVE

To examine the association between individual, cumulative leisure noise exposure (CLNE), acceptable yearly exposure (AYE) and tinnitus among a nationally representative sample of Canadians.

DESIGN

In-person household questionnaires were used to evaluate leisure noise exposure across age, sex, household income and tinnitus: ever experienced, previous year, frequent, bothersome. High (≥85 dBA, LEX), low (<85 dBA, LEX) CLNE and AYEs were defined according to occupational limits.

STUDY SAMPLE

A randomised sample of 10,460 respondents, aged 6-79, completed questionnaires between 2012 and 2015. Results: Tinnitus prevalence was highest among young adults and teenagers (50% for both). Frequent and bothersome tinnitus afflicted one-third and 18.1% of Canadians, respectively. Men had higher tinnitus prevalence while women had increased bothersome tinnitus. For most ages, elevated tinnitus odds ratios (ORs) were associated with: (1) high, low CLNE and AYEs ≥1 and, (2) high exposure from individual sources: loud home/car stereo listening, power tools, gasoline engines, highway motorcycle/snowmobile driving. Loud personal listening device usage was associated with tinnitus ORs doubling (ages 6-11) and ≥5 or < 5 years of loud usage, with increased tinnitus ORs (ages 12-19).

CONCLUSION

Community and/or school-based educational outreach would be beneficial to increase awareness of loud leisure noise exposure and tinnitus.

Combining unequal variance signal detection theory with the health belief model to optimize shared decision making in tinnitus patients: part 1-model development

Introduction

The results from different Cochrane studies justify considerable professional equipoise concerning different treatment options for tinnitus. In case of professional equipoise, Shared Decision Making (SDM) is an indispensable tool for guiding patients to the intervention that best fits their needs. To improve SDM we developed a method to assess the accuracy and utility of decisions made by tinnitus patients when freely choosing between different treatment options during their patient journey. The different treatment options were audiological care and psychosocial counseling.

Methods

We developed a statistical model by combining Signal Detection Theory (SDT) with the Health Belief Model (HBM). HBM states that perceived severity of an illness is strongly related to sick-role behavior. As proxies for perceived severity, we selected hearing loss and Tinnitus Handicap Inventory (THI) score at baseline. Next, we used these proxies as predictors in linear regression models based on SDT to determine the likelihood ratio of true positive decisions (choosing a treatment option and experiencing an improvement of more than 7 points in THI-score) and false positive decisions (choosing a treatment option and experiencing an improvement of less than 7 points in THI-score) for audiological care and psychosocial counseling, respectively. Data was gathered in a prospective cohort of 145 adults referred for tinnitus care to an outpatient audiology clinic in the Netherlands. The participants were asked to decide freely on uptake of audiological care (provision of hearing aids with or without a sound generator) and uptake of psychosocial counseling. Logistic regression with Bayesian inference was used to determine the cumulative distribution functions and the probability density functions of true positive decisions and false positive decisions as function of hearing loss and baseline THI-score for both treatment options, respectively. With the cumulative distribution functions, we determined the accuracy of the decisions. With the probability density functions we calculated the likelihood ratios of true positive decisions versus false positive decisions as function of hearing loss and baseline THI-score. These likelihood ratio functions allow assessment of the utility of the decisions by relating a decision criterion to perceived benefits and costs.

Results

Baseline THI-score drives decisions about psychosocial counseling and hearing loss drives decisions about audiological care. Decisions about psychosocial counseling are more accurate than decisions about audiological care. Both decisions have a low accuracy (0.255 for audiological care and  - 0.429 for psychosocial counseling), however. For decisions about audiological care the unbiased decision criterion is 37 dB(HL), meaning that a lenient decision criterion (likelihood ratio < 1) is adopted by patients with a hearing loss below 37 dB and a strict criterion (likelihood ratio > 1) by patients with a hearing loss exceeding 37 dB. For psychosocial counseling uptake the decision criterion is always strict, regardless of baseline THI-score. The distributions of the populations, that do and do not experience a clinically important change in THI-score, have unequal variances for psychosocial counseling, while they have almost equal variances for audiological care.

Discussion

Combining SDT and HBM can help assess accuracy and utility of patient decisions and thus may provide valuable information that can help to improve SDM by combining patient related outcome measures, decision drivers, and perceived benefits and costs of a treatment.

Effect of transcranial direct current stimulation on tinnitus modulation: A randomized, double-blind, and placebo-controlled clinical trial: Effect of tDCS on tinnitus modulation: A clinical trial

OBJECTIVES

To evaluate the short and long-term effects of anodal tDCS (a-tDCS) targeting the left temporoparietal area (LTA) on tinnitus severity, annoyance, and loudness.

METHODS

This is a double-blind, randomized, sham-controlled, and parallel-group clinical trial. A total of 42 individuals with tinnitus were randomized to a-tDCS (n = 24) or sham tDCS (n = 18). The a-tDCS group received tDCS over the LTA during five consecutive day sessions (2 mA, 20 min). The sham group received a placebo current with the same characteristics as the a-tDCS group. Participants were assessed at baseline, after the fifth session, and at the 30-day follow-up, using hearing assessments and symptom questionnaires.

RESULTS

There was no effect of comparison between groups or interaction effect (time x group) in all hearing assessments and symptom questionnaires. There was only a main effect of time for Tinnitus Handicap Inventory - THI [F(1.642, 45.988) = 5.128; p = 0.014; η2 = 0.155]. Bonferroni post hoc showed that there was a significant difference in THI in the sham group between pre and post-treatment [CI (0.107, 14.643; p = 0.046)]. However, there was no difference between pre-treatment and follow-up THI, or between post-treatment and follow-up THI. There was no treatment effect on tinnitus severity (assessed by Tinnitus Functional Inventory - TFI), tinnitus annoyance or loudness (assessed by Visual Analogue Scale - VAS), or tinnitus pitch, loudness or minimum masking level (assessed by tinnitometry).

CONCLUSION

Five consecutive sessions of a-tDCS targeting LTA do not improve tinnitus severity, annoyance, and loudness. Future studies should investigate if other tDCS protocols are effective or a combination of tDCS with other forms of treatment.

Comparative study on structural and functional brain differences in mild cognitive impairment patients with tinnitus

Objective

Tinnitus may be associated with various brain changes. However, the degenerative changes in patients with tinnitus have not been extensively investigated. We aimed to evaluate degenerative, structural, and functional brain changes in patients with mild cognitive impairment (MCI) who also suffer from tinnitus.

Materials and methods

This study included participants aged 60 to 80 years with MCI and a hearing level better than 40 dB. The participants were classified into two groups: MCI with tinnitus (MCI-T) and MCI without tinnitus (MCI-NT). All patients underwent Tinnitus Handicap Inventory (THI), 3 T brain MRI, F18-florapronol PET, and F18-FDG PET.

Results

The MCI-T group exhibited higher β-amyloid deposition in the superior temporal gyrus, temporal pole, and middle temporal gyrus compared to the MCI-NT group (p < 0.05 for all). Additionally, the MCI-T group showed increased metabolism in the inferior frontal gyrus, insula, and anterior cingulate cortex (ACC) (p < 0.005 for all). The THI score was strongly correlated with increased volume in the insula, ACC, superior frontal gyrus, supplementary motor area, white matter near the hippocampus, and precentral gyrus (p < 0.05 for all). Moreover, the MCI-T group demonstrated higher metabolic activity in the default mode network (DMN) and lower activity in the executive control network (ECN) (p < 0.05 for all). In the MCI-T group, the posterior DMN was positively correlated with the visual network and negatively with the ECN, whereas in the MCI-NT group, it correlated positively with the ECN.

Conclusion

The MCI-T group exhibited greater β-amyloid accumulation in the auditory cortex and more extensive changes across various brain networks compared with the MCI-NT group, potentially leading to diverse clinical symptoms such as dementia with semantic deficits or depression. Tinnitus in MCI patients may serve as a biomarker for degenerative changes in the temporal lobe and alterations in brain network dynamics.

Tinnitus as a Potential Risk Factor for Uveitis: A 14-Year Nationwide Population-Based Cohort Study in Taiwan

BACKGROUND

Tinnitus and uveitis have shared commonality in pathophysiology in terms of autoimmunity. However, no studies that have linked any association between the conditions of tinnitus and uveitis.

METHODS

This is a retrospective study conducted from the Taiwan National Health Insurance database in order to investigate whether tinnitus patients are at increased risk of uveitis. Patients newly diagnosed with tinnitus between 2001 and 2014 were recruited and followed up until 2018. The endpoint of interest was a diagnosis of uveitis.

RESULTS

A total of 31,034 tinnitus patients and 124,136 matched comparisons were analyzed. Tinnitus patients were found to have a significantly higher cumulative incidence for uveitis than those without the diagnosis of tinnitus with incidence rate of 1.68 (95% CI 1.55-1.82) per 10 000 person-months for tinnitus group and 1.48 (95% CI 1.42-1.54) per 10 000 person-months for non-tinnitus group.

CONCLUSION

Tinnitus patients were found to have increased risk of developing uveitis.

Acupuncture for Tinnitus: A Scoping Review of Clinical Studies

BACKGROUND

Acupuncture treatment for tinnitus has received attention owing to its potential as an alternative to conventional treatment modalities. We conducted a scoping review to identify detailed information on acupuncture treatment methods used in clinical studies and to provide useful information for practitioners, patients, and researchers.

METHODS

MEDLINE, Cochrane Central Register of Controlled Trials (CENTRAL), Embase, Oriental Medicine Advanced Searching Integrated System (OASIS), Korean Research Information Sharing Service (RISS), DataBase Periodical Information Academic (DBPIA), and the China National Knowledge Infrastructure (CNKI) were searched from their inception to December 2023. This review included single-arm trials, open-label randomized controlled trials (RCTs), and double-blind RCTs using needle-type acupuncture to treat tinnitus in English, Chinese, and Korean. We investigated basic and detailed information on the acupuncture treatment methods, assessment methods, and study outcomes. Network analysis was also conducted to evaluate the centrality between acupoints in the double-blind RCTs.

RESULTS

We included 106 articles. There were 11 single-arm trials, 90 open-label RCTs, and 5 double-blind RCTs. Most (89.6%) of these studies were conducted in China. Manual acupuncture was the most common type of acupuncture in treatment group. A total of 119 acupuncture points were used 1,138 times. The most frequently used acupoints were local points around the ear (TE17, GB2, SI19, and TE21). Both local and distant acupoints were used simultaneously in these studies. The treatment duration of 20-39 days, 10 to 19 sessions of treatment, the mean acupuncture duration of 30 min, needle diameter of 0.30 mm × 40 mm, and needling depth over 30 mm and less than 50 mm were confirmed as the most common.

CONCLUSION

These study outcomes will enable future acupuncture studies on tinnitus to perform more effective and standardized acupuncture treatments in selecting acupoints and procedures. Furthermore, the study has implications for informing clinicians and students about more impactful acupuncture strategies for addressing tinnitus.

Hintergrund

Die Anwendung von Akupunktur bei Tinnitus erhält seit einiger Zeit Aufmerksamkeit als potenzielle Alternative zu konventionellen Behandlungsmodalitäten. Wir führten einen Scoping-Review durch, um detaillierte Informationen zu den in klinischen Studien angewandten Akupunktur-Behandlungsmethoden zu sammeln und nützliche Informationen für Praktiker, Patienten und Forscher bereitzustellen.

Methoden

MEDLINE, Cochrane Central Register of Controlled Trials (CENTRAL), Embase, Oriental Medicine Advanced Searching Integrated System (OASIS), Korean Research Information Sharing Service (RISS), DataBase Periodical Information Academic (DBPIA) und die China National Knowledge Infrastructure (CNKI) wurden von ihrem jeweiligen Beginn bis Dezember 2023 durchsucht. In diese Übersichtsarbeit wurden einarmige Studien, offene, randomisierte, kontrollierte Studien (RCTs) sowie doppelt verblindete RCTs zu Nadel-Akupunktur zur Behandlung von Tinnitus in englischer, chinesischer und koreanischer Sprache einbezogen. Wir untersuchten grundlegende und detaillierte Informationen zu den Akupunktur-Behandlungsmethoden, Untersuchungsmethoden und Studienergebnissen. Außerdem wurden Netzwerkanalysen zur Beurteilung der Zentralität zwischen Akupunkten in den doppelt verblindeten RCTs durchgeführt.

Ergebnisse

106 Artikel wurden eingeschlossen. Sie behandelten 11 einarmige Studien, 90 offene RCTs und 5 doppelt verblindete RCTs. Die meisten (89,6%) dieser Studien waren in China durchgeführt worden. Manuelle Akupunktur war die häufigste Form der Akupunktur in den Behandlungsgruppen. 119 Akupunkturpunkte wurden insgesamt 1’138 Mal verwendet. Die am häufigsten verwendeten Akupunkte waren lokale Punkte im Bereich des Ohrs (TE17, GB2, SI19 und TE21). Jedoch wurden in den Studien lokale und entfernte Akupunkte gleichzeitig angewendet. Außerdem wurde festgestellt, dass die Behandlungsdauer am häufigsten 20 bis 39 Tage betrug, die Zahl der Sitzungen 10 bis 19, die mittlere Akupunkturdauer 30 Minuten, die Nadelgröße 0.30 mm × 40 mm und die Einstichtiefe zwischen 30 mm und weniger als 50 mm.

Schlussfolgerung

Diese Studienergebnisse bieten eine Grundlage für künftige Studien zu Akupunktur bei Tinnitus, um durch die Auswahl der Akupunkte und Verfahren wirksamere und standardisierte Akupunkturbehandlungen durchzuführen. Darüber hinaus hat die Studie Implikationen für die Aufklärung von Praktikern und Schülern über wirkungsvollere Akupunkturstrategien zur Behandlung von Tinnitus.

Cross-Modal Tinnitus Remediation: A Tentative Theoretical Framework

Tinnitus is a prevalent hearing-loss deficit manifested as a phantom (internally generated by the brain) sound that is heard as a high-frequency tone in the majority of afflicted persons. Chronic tinnitus is debilitating, leading to distress, sleep deprivation, anxiety, and even suicidal thoughts. It has been theorized that, in the majority of afflicted persons, tinnitus can be attributed to the loss of high-frequency input from the cochlea to the auditory cortex, known as deafferentation. Deafferentation due to hearing loss develops with aging, which progressively causes tonotopic regions coding for the lost high-frequency coding to synchronize, leading to a phantom high-frequency sound sensation. Approaches to tinnitus remediation that demonstrated promise include inhibitory drugs, the use of tinnitus-specific frequency notching to increase lateral inhibition to the deafferented neurons, and multisensory approaches (auditory-motor and audiovisual) that work by coupling multisensory stimulation to the deafferented neural populations. The goal of this review is to put forward a theoretical framework of a multisensory approach to remedy tinnitus. Our theoretical framework posits that due to vision's modulatory (inhibitory, excitatory) influence on the auditory pathway, a prolonged engagement in audiovisual activity, especially during daily discourse, as opposed to auditory-only activity/discourse, can progressively reorganize deafferented neural populations, resulting in the reduced synchrony of the deafferented neurons and a reduction in tinnitus severity over time.

Auditory training for tinnitus treatment: a scoping review

OBJECTIVES

Our study aimed to verify the evidence of auditory training employed in the audiological treatment of tinnitus in adults and older adults.

METHODS

Scoping review based on a search for articles in journals available in MEDLINE (PubMed), Embase (Elsevier), LILACS (BVS), and Cochrane Library. Titles and abstracts of the retrieved articles were assessed by peers, following the eligibility criteria; they were afterward read in full text, and the references were hand searched in the results found. Studies' level of evidence was classified into very high (Level A+), high (Level A), moderate (Level B), limited (Level C), low (Level D), or very low (Level D-) based on the Critically Appraised Topics.

RESULTS

2160 records were identified in the searching stage and 15 studies were eligible for data extraction. Study design, sample characterization, auditory training tasks, sound stimuli, outcome measures, and results were extracted. Frequency discrimination training was the most frequent strategy, followed by auditory attentional skills training and multisensory training. Almost all studies with daily auditory training sessions reported significant benefits demonstrated in at least one outcome measure. Studies that used auditory discrimination training and attentional auditory skill stimulation to treat tinnitus obtained quality evidence levels ranging from limited to high (C‒A) and studies that applied multisensory training or attentional training combined with counseling and passive listening in tinnitus patients reached a high-quality evidence level (A).

CONCLUSION

Recent studies had higher levels of evidence and considered attentional factors and multisensory pathways in auditory training strategies.

Depolarization shift in the resting membrane potential of inferior colliculus neurons explains their hyperactivity induced by an acoustic trauma

Introduction

Neuronal hyperactivity has been associated with many brain diseases. In the auditory system, hyperactivity has been linked to hyperacusis and tinnitus. Previous research demonstrated the development of hyperactivity in inferior colliculus (IC) neurons after sound overexposure, but the underlying mechanism of this hyperactivity remains unclear. The main goal of this study was to determine the mechanism of this hyperactivity.

Methods

Experiments were performed on CBA/CaJ mice in a restrained, unanesthetized condition using intracellular recordings with sharp microelectrodes. Recordings were obtained from control (unexposed) and unilaterally sound overexposed groups of mice.

Results

Our data suggest that sound exposure-induced hyperactivity was due to a depolarizing shift of the resting membrane potential (RMP) in the hyperactive neurons. The half width of action potentials in these neurons was also decreased after sound exposure. Surprisingly, we also found an RMP gradient in which neurons have more hyperpolarized RMPs with increasing depth in the IC. This gradient was altered in the overexposed animals.

The clinical effects of modified tinnitus relieving sound (MTRS) for chronic tinnitus: protocol for a randomized controlled trial

INTRODUCTION

Chronic subjective tinnitus has become an increasingly serious hazard that affects the health-related quality of life for millions of people. Due to the lack of curative treatment strategies, this study aims to introduce a novel acoustic therapy named the modified tinnitus relieving sound (MTRS) for tinnitus and to evaluate the efficacy of MTRS in comparison with unmodified music (UM) which served as a control.

METHODS AND ANALYSIS

A randomized, double-blinded, controlled, clinical trial will be carried out. Sixty-eight patients with subjective tinnitus will be recruited and randomly allocated into two groups in 1:1 ratio. The primary outcome is Tinnitus Handicapped Inventory (THI); the secondary outcomes are the Hospital Anxiety and Distress Scale (HADS; HADS subscales for Anxiety (HADS-A) and Depression (HADS-D)), Athens Insomnia Scale (AIS), the visual analog scale (VAS) for tinnitus, and tinnitus loudness matched by sensation level (SL). Assessment will be performed at baseline and at 1, 3, 9, and 12 months post-randomization. The sound stimulus will be persistent until 9 months after randomization, and be interdictory in the last three months. Data collected during the intervention process will be analyzed and compared to baseline.

ETHICS AND DISSEMINATION

This trial received ethical approval from the Institutional Review Board (IRB) of Eye & ENT Hospital of Fudan University (No. 2017048). The study results will be disseminated via academic journals and conferences.

FUNDING

This study is supported by the Shanghai Shenkang Development Program (SHDC12019119), the Excellent Doctors-Excellent Clinical Researchers Program (SYB202008), the Shanghai Rising-Star Program (23QC1401200), the Shanghai Rising Stars of Medical Talent Youth Development Program (2021-99), the National Natural Science Foundation of China (81800912), and the National Natural Science Foundation of Shanghai (21ZR1411800).

TRIAL REGISTRATION

ClinicalTrials.gov NCT04026932. Registered on 18 July 2019.

A clinical trial of a patient-customized virtual reality intervention for tinnitus

Virtual reality (VR) has recently been used as a clinical treatment because it can efficiently simulate situations that are difficult to control in real-world settings. In our study, we assessed the potential of VR in patients with chronic subjective tinnitus. An evaluation of its clinical benefits was performed based on analyses of patient electroencephalograms (EEGs) and by questionnaire responses after 6–8 weeks of patient involvement in our VR-based alleviation program. Clinical trials were performed at a tertiary academic hospital. Nineteen patients (aged 33–64 years) who visited our hospital with chronic subjective tinnitus over 3 months were enrolled in the study. The intervention consisted of trashing the tinnitus avatar in VR. We expected that the patients would have the subjective feeling of controlling tinnitus through our intervention. The VR environment comprised four different sessions in four different settings: a bedroom, a living room, a restaurant, and a city street. We analyzed changes in the source activities of the prefrontal regions related to tinnitus in these patients using standardized low-resolution brain electromagnetic tomography. The Tinnitus Handicap Inventory (THI), the total score (from 50.11 to 44.21, P = 0.046) and the grade (from 3.16 to 2.79, P = 0.035) were significantly improved after the VR-based tinnitus treatment program (P < 0.05). The Pittsburgh Sleep Quality Index also showed improved outcomes (P = 0.025). On the other hand, a Tinnitus Handicap Questionnaire, Quality of Life Assessment (WHO-QOL), Hospital Anxiety and Depression Scale, Profile of Mood States revealed no significant change after the intervention. The baseline EEG data showed that brain activity in the orbitofrontal cortex significantly increased in the alpha and theta frequency bands. Furthermore, patients who showed a THI score improvement after the intervention showed specific increases in brain activity for the theta and high beta bands in the orbitofrontal cortex. Our findings suggest that the virtual reality-based program, as in parts of cognitive behavioral treatment, may help to alleviate tinnitus-related distress in patients with chronic subjective tinnitus.

The Interrelationship of Tinnitus and Hearing Loss Secondary to Age, Noise Exposure, and Traumatic Brain Injury

OBJECTIVE

Tinnitus has been the No. 1 disability at the Veteran Administration for the last 15 years, yet its interaction with hearing loss secondary to etiologies such as age, noise trauma, and traumatic brain injuries remains poorly characterized. Our objective was to analyze hearing loss and tinnitus, including audiogram data, of the Million Veteran Program within the context of military exposures in an aging population.

DESIGN

Health records, questionnaires, audiograms, and military data were aggregated for 758,005 Veteran participants in the Million Veteran Program 2011 to 2020, with relative risks (RR) calculated for ancestries, sex, hearing loss and military exposures such as combat, blast, and military era served. A multivariate model with significant demographic measures and exposures was then analyzed. Next, audiogram data stratified by sex were compared for those with and without tinnitus by two methods: first, mean thresholds at standard frequencies were compared to thresholds adjusted per ISO 7029:2000E age and sex formulae. Second, levels for those ≤40 years of age were compared with those 41 and older. Finally, a proportional hazards model was examined to ascertain the timing between the onset of tinnitus and hearing loss, calculated separately for electronic health record diagnoses (ICD) and self-report.

RESULTS

Tinnitus was either self-reported, diagnosed, or both in 37.5% (95% CI, 37.4 to 37.6), mean age 61.5 (95% CI, 61.4 to 61.5), range 18 to 112 years. Those with hearing loss were 4.15 times (95% CI, 4.12 to 4.15) as likely to have tinnitus. Americans of African descent were less likely to manifest tinnitus (RR 0.61, 95% CI, 0.60 to 0.61), as were women (RR 0.65, 95% CI, 0.64 to 0.65). A multivariate model indicated a higher RR of 1.73 for traumatic brain injury (95% CI, 1.71 to 1.73) and daily combat noise exposure (1.17, 95% CI, 1.14 to 1.17) than age (0.998, 95% CI, 0.997 to 0.998). Subjects ≤40 years of age had small but significantly elevated hearing thresholds through all standard frequencies compared to Veterans without tinnitus, and the effect of tinnitus on hearing thresholds diminished with age. In the hazard model, those >40 with new onset of tinnitus were at risk for hearing loss sooner and with greater incidence than those who were younger. The rate of hearing loss following tinnitus approached 100%. In contrast, only approximately 50% of those who self-reported hearing loss initially were at risk for later hearing loss, in contrast to ICD comparison, where those with ICD of hearing loss were more likely to sustain an ICD of tinnitus subsequently.

CONCLUSIONS

Evidence suggests that the occurrence of tinnitus in the military is more closely related to environmental exposures than to aging. The finding that tinnitus affects hearing frequencies across the audiogram spectrum suggests an acoustic injury independent of tonotopicity. Particularly for males >40, tinnitus may be a harbinger of audiologic damage predictive of later hearing loss.

Systematic review and meta-analysis on the effect of continuous subjective tinnitus on attention and habituation

Background

Attention and habituation are two domains known to play key roles in the perception and maintenance of tinnitus. The heterogeneous nature of tinnitus and the methodologies adopted by various studies make it difficult to generalize findings. The current review aims at assessing and synthesizing evidence on the possible roles of attention and habituation in continuous subjective tinnitus.

Methodology

The literature search included five databases (PubMed, Scopus, Web of Sciences, CINAHL and ProQuest) that resulted in 1,293 articles, published by July 2019. Studies on attention and/or habituation in individuals with tinnitus using either behavioural or electrophysiological tests were included in the review after a quality assessment.

Results

Seventeen studies on attention in tinnitus were included in the narrative synthesis. Two meta-analyses were performed to assess the role of attention in tinnitus using a behavioural methodology (z = 4.06; p < 0.0001) and P300 amplitude (z = 2.70; p = 0.007) with 531 participants. With respect to habituation, the review indicates the lack of quality articles for habituation inclusion in the narrative synthesis.

Conclusions

The review highlights that selective domains of attention were consistently impaired in individuals with tinnitus. Habituation, on the other hand, needs further exploration.

Effect of Unilateral Acoustic Trauma on Neuronal Firing Activity in the Inferior Colliculus of Mice

Neural hyperactivity induced by sound exposure often correlates with the development of hyperacusis and/or tinnitus. In laboratory animals, hyperactivity is typically induced by unilateral sound exposure to preserve one ear for further testing of hearing performance. Most ascending fibers in the auditory system cross into the superior olivary complex and then ascend contralaterally. Therefore, unilateral exposure should be expected to mostly affect the contralateral side above the auditory brain stem. On the other hand, it is well known that a significant number of neurons have crossing fibers at every level of the auditory pathway, which may spread the effect of unilateral exposure onto the ipsilateral side. Here we demonstrate that unilateral sound exposure causes development of hyperactivity in both the contra and ipsilateral inferior colliculus in mice. We found that both the spontaneous firing rate and bursting activity were increased significantly compared to unexposed mice. The neurons with characteristic frequencies at or above the center frequency of exposure showed the greatest increase. Surprisingly, this increase was more pronounced in the ipsilateral inferior colliculus. This study highlights the importance of considering both ipsi- and contralateral effects in future studies utilizing unilateral sound exposure.

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.

•

Global cerebral blood flow is reduced in tinnitus.

•

Tinnitus severity is negatively correlated with cerebral blood flow globally.

•

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

•

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

•

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

Auditory sensation with affective agnosia: A prevalence of alexithymia among tinnitus patients

OBJECTIVES

The aim of the present study was to determine the prevalence and association of alexithymia, depression, and anxiety in patients affected by tinnitus.

METHODS

The study was conducted among the patients referred for audiometric evaluation for tinnitus. They were further evaluated with the Hospital Anxiety and Depression Scale, the Tinnitus Handicap Inventory, and the Toronto Alexithymia Scale. Analysis was done for prevalence and the sample was categorized as high and low tinnitus handicap subgroups, and mean scores of alexithymia, anxiety, and depression were compared.

RESULTS

A total of 70 patients (55.7% - male and 44.3% - female) with a mean age of 33.17 ± 12.24 years were finally analyzed. The severity of tinnitus was most severe (34.3%), followed by moderate (20%), catastrophic (18.6%), mild (17.1%), and slight (10%). The prevalence of alexithymia, anxiety, and depression among patients of tinnitus was found to be 65.7%, 37.1%, and 20%, respectively. The high tinnitus handicap group showed higher scoring on total alexithymia score, anxiety, and depression and higher scoring with describing emotion and identification of emotion, but there was no difference for the subscale of externally oriented thinking.

CONCLUSIONS

The study found a prevalence of alexithymia, anxiety, and depression as 65.7%, 37.1%, and 20%, respectively, among patients of tinnitus, and problem of describing and identification of emotion are associated with higher tinnitus handicap.

Chronic Tinnitus Exhibits Bidirectional Functional Dysconnectivity in Frontostriatal Circuit

Purpose

The phantom sound of tinnitus is considered to be associated with abnormal functional coupling between the nucleus accumbens (NAc) and the prefrontal cortex, which may form a frontostriatal top-down gating system to evaluate and modulate sensory signals. Resting-state functional magnetic resonance imaging (fMRI) was used to recognize the aberrant directional connectivity of the NAc in chronic tinnitus and to ascertain the relationship between this connectivity and tinnitus characteristics.

Methods

Participants included chronic tinnitus patients (n = 50) and healthy controls (n = 55), matched for age, sex, education, and hearing thresholds. The hearing status of both groups was comparable. On the basis of the NAc as a seed region, a Granger causality analysis (GCA) study was conducted to investigate the directional connectivity and the relationship with tinnitus duration or distress.

Results

Compared with healthy controls, tinnitus patients exhibited abnormal directional connectivity between the NAc and the prefrontal cortex, principally the middle frontal gyrus (MFG), orbitofrontal cortex (OFC), and inferior frontal gyrus (IFG). Additionally, positive correlations between tinnitus handicap questionnaire (THQ) scores and increased directional connectivity from the right NAc to the left MFG (r = 0.357, p = 0.015) and from the right MFG to the left NAc (r = 0.626, p < 0.001) were observed. Furthermore, the enhanced directional connectivity from the right NAc to the right OFC was positively associated with the duration of tinnitus (r = 0.599, p < 0.001).

Conclusion

In concurrence with expectations, tinnitus distress was correlated with enhanced directional connectivity between the NAc and the prefrontal cortex. The current study not only helps illuminate the neural basis of the frontostriatal gating control of tinnitus sensation but also contributes to deciphering the neuropathological features of tinnitus.

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.

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.

Efficacy of Chinese herb Cistanche Yishen granules in treatment of tinnitus for patients with chronic nephritis

OBJECTIVE

This study aimed to investigate the efficacy of Chinese herb Cistanche Yishen granules (CYG) in the treatment of tinnitus for patients with chronic nephritis.

METHODS

A total of 89 adult patients were diagnosed with chronic glomerulonephritis from January 2016 to December 2017. All the patients were randomly divided into two groups, such as the control group and the CYG group. The efficacy of tinnitus was determined using tinnitus handicap inventory (THI), Pittsburgh sleep quality index (PSQI), pure tone audiometry (PTA), speech reception threshold (SRT), and visual analog scale (VAS) for tinnitus loudness and annoyance.

RESULTS

In both these two groups of patients, values of THI, PSQI, PTA, SRT, and VAS for tinnitus loudness and annoyance were significantly decreased after the treatment compared with those before treatment. However, all values in CYG group after the treatment were significantly lower than those in the control group.

CONCLUSION

CYG could apparently release the tinnitus symptoms in the patients with chronic nephritis. This study might give more clinical evidence for Cistanche in the treatment of tinnitus and give a new treatment method for the patients with tinnitus.

Tinnitus Is Associated with a Higher Risk of Benign Brain Tumors: A Nationwide, Population-Based Secondary Cohort Study of Young and Middle-Aged Adults

BACKGROUND

It remains unclear whether tinnitus is associated with a higher risk of benign or malignant brain tumors in humans. Therefore, the aim of this secondary study was to investigate the risk of brain tumors in adult with tinnitus using data from a nationwide health claims research database.

METHODS

Patients aged 20-50 years who were newly diagnosed with tinnitus were identified from the Taiwan's National Health Insurance Research Database and they served as the study cohort. A comparison cohort was formed by using patients without tinnitus from the same database with frequency matching (4: 1) by 10-year age interval and gender to the patients in the tinnitus cohort. Cox proportional hazards models were used to calculate the adjusted hazard ratios (AHR) for benign and malignant brain tumors in patients with tinnitus, adjusting for age, gender, and comorbidities.

RESULTS

There were 15,819 patients in the tinnitus cohort and 63,276 in the comparison cohort. A significantly higher proportion of patients with tinnitus had benign brain tumor (p = 0.003) and all 11 comorbid conditions (p < 0.001) compared to those without tinnitus. Cox proportional hazards regression analysis performed on the basis of age, gender, and the 11 comorbidities revealed that tinnitus was independently associated with a higher risk for benign brain tumor (AHR 1.65, 95% CI 1.24-2.20, p = 0.001) and but not with malignant brain tumors (AHR 1.66, 95% CI 0.93-2.94, p = 0.085).

CONCLUSIONS

Findings from this secondary cohort analysis indicated that tinnitus is associated with a higher risk of benign brain tumors.

Increased risk of tinnitus in patients with chronic kidney disease: A nationwide, population-based cohort study

Tinnitus mostly results from central and peripheral auditory pathology. Chronic kidney disease (CKD) is a major risk factor for cerebrovascular disease. However, no studies have evaluated the association between tinnitus and CKD. The aim of this study is to investigate the risk of tinnitus in patients with CKD. This retrospective cohort study was conducted using Taiwan National Health Insurance Research Database from 2000 to 2010. We established a CKD group (n = 185,430) and a non-CKD comparison group (n = 556,290) to investigate the incidence of tinnitus. Cox proportional hazard regression analysis was used to evaluate the effects of CKD on tinnitus risk. The results showed CKD significantly increased the risk of tinnitus (adjusted hazard ratio, 3.02; 95% CI, 2.655-3.456, P<0.001). A subgroup analysis revealed the increase in risk of tinnitus is more in CKD patients with heart failure (adjusted hazard ratio, 9.975; 95% CI, 5.001-18.752) and diabetes mellitus (adjusted hazard ratio, 3.712; 95% CI, 2.856-5.007). Furthermore, compared to non-CKD patients, the risk of tinnitus was increased 4.586-fold (95% CI, 2.399-6.7) in CKD patients with dialysis and 2.461-fold (95% CI, 1.033-3.454) in CKD patients without dialysis. This study is the first to report that CKD is associated with an increased risk of tinnitus. Among CKD cohort, patients with dialysis are at a higher risk of tinnitus than those without dialysis.

Results of an Interdisciplinary Day Care Approach for Chronic Tinnitus Treatment: A Prospective Study Introducing the Jena Interdisciplinary Treatment for Tinnitus

Objective: Considering the heterogeneity of the symptoms shown by patients suffering from chronic tinnitus, there are surprisingly few interdisciplinary treatments available, and mostly available only for inpatients. In order to provide an interdisciplinary treatment, we developed a day care concept in which each patient was treated by an ENT doctor, a cognitive behavioral therapist, a specialist for medical rehabilitation and an audiologist (Jena Interdisciplinary Treatment for Tinnitus, JITT). The aim of this study was to observe the changes of tinnitus related distress due to interdisciplinary day care treatment and to determine which factors mediate this change.

Subjects and Methods: Tinnitus annoyance was measured using the Tinnitus Questionnaire on 308 patients with chronic tinnitus. They were treated in the day care unit over five consecutive days between July 2013 and December 2014. Data were collected before treatment when screened (T0), at the beginning (T1) and at the end of the 5 day treatment (T2), as well as 20 days (T3) and 6 months after treatment (T4).

Results: Overall, tinnitus annoyance improved significantly from the screening day to the beginning of treatment, and to a much larger degree from the beginning to the end of treatment. The treatment outcome remained stable 6 months after treatment. Patients with the following symptoms displayed higher tinnitus annoyance at T0: dizziness at tinnitus onset, tinnitus sound could not be masked with background noise, tinnitus worsening during physical stress, comorbid psychiatric diagnosis, higher age and higher hearing loss. Loudness of tinnitus perceived in the right ear correlated with tinnitus annoyance significantly. Demographic, tinnitus and strain variables could only explain 12.8% of the variance of the change in tinnitus annoyance from T0 to T4. Out of 39 predictors, the only significant ones were “sick leave 6 months before treatment” and “tinnitus annoyance at T0.”

Conclusion: The newly developed JITT represents a valuable treatment for chronic tinnitus patients with improvement remaining stable for at least 6 months after treatment. Using a large number of variables did not allow predicting treatment outcome which underlines the heterogeneity of tinnitus.

Long-Lasting forward Suppression of Spontaneous Firing in Auditory Neurons: Implication to the Residual Inhibition of Tinnitus

Tinnitus is the perception of a sound that has no external source. Sound stimuli can suppress spontaneous firing in auditory neurons long after stimulus offset. It is unknown how changes in sound stimulus parameters affect this forward suppression. Using in vivo extracellular recording in awake mice, we found that about 40 % of spontaneously active inferior colliculus (IC) neurons exhibited forward suppression of spontaneous activity after sound offset. The duration of this suppression increased with sound duration and lasted about 40 s following a 30-s stimulus offset. Pure tones presented at the neuron's characteristic frequency (CF) were more effective in triggering suppression compared to non-CF or wideband noise stimuli. In contrast, non-CF stimuli often induced forward facilitation. About one third of IC neurons exhibited shorter suppression durations with each subsequent sound presentation. These characteristics of forward suppression are similar to the psychoacoustic properties of residual inhibition of tinnitus: a phenomenon of brief (about 30 s) suppression of tinnitus observed in tinnitus patients after sound presentations. Because elevated spontaneous firing in central auditory neurons has been linked to tinnitus, forward suppression of this firing with sound might be an underlying mechanism of residual inhibition.

Small Compartment Toxicity: CN VIII and Quality of Life: Hearing Loss, Tinnitus, and Balance Disorders

Life experiences, industrial/environmental exposures, and administration of Food and Drug Administration (FDA)-approved drugs may have unintended but detrimental effects on peripheral and central auditory pathways. Most relevant to the readership of this journal is the role that drug treatments approved by the FDA as safe and effective appear to interact with 3 independent modes of toxicity within the small compartment of the ear. What may seem to be trivial drug-induced toxicity has the potential to change important measures of quality of life and functional capacity of mid- to late-life patients. Drugs meant to treat can become the source of interference in the activities of daily living, and as a result, treatment compliance may be jeopardized. Ototoxicity has been defined as the tendency of certain therapeutic agents and other chemical substances to cause functional impairments and cellular degeneration of the tissues of the inner ear resulting in hearing loss. However, one of the largest contributors to hospitalizations is fall-related injuries in the elderly patients associated with disorders of vestibular function linked to progressive and drug-induced toxicities. Tinnitus affects 35 to 50 million adults representing approximately 25% of the US population, with 12 million seeking medical care and 2 to 3 million reporting symptoms that were severely debilitating. This review is intended to highlight these targets of neurotoxicity that threaten the usefulness of drug treatments deemed safe and effective prior to access by the general public.

The relationship between ultra-high frequency thresholds and transient evoked otoacoustic emissions in adults with tinnitus

Background: The possible role of cochlear function in tinnitus generation is still a matter of debate. To assess the role of outer hair cell dysfunction in tinnitus and its possible relationship with ultra-high frequency (UHF) hearing sensitivity, transient evoked otoacoustic emissions (TEOAE) and UHF hearing thresholds were investigated in normal hearing individuals with and without tinnitus. Methods: Eighteen individuals with tinnitus and 22 without tinnitus participated in this study. TEOAE was recorded with click stimulus at 80 dBpeSPL. UHF pure tone audiometry was performed at 10, 12.5, 16, and 18 kHz. Results: TEOAE was significantly abnormal in 72.2% of the tinnitus, and 18.2% of the control groups (p=0.001). The individuals with tinnitus had significantly poorer UHF hearing sensitivity compared to the control group at 12.5 and 18 kHz (p≤0.048). There was a stronger correlation between increasing UHFs hearing threshold and decreasing SNRs of TEOAEs in the tinnitus group compared to the controls. Conclusion: Our study revealed poorer UHF hearing thresholds and more TEOAE abnormalities in normal hearing individuals with tinnitus compared to the controls. Perhaps the alterations in the basal cochlea, following a decrease in UHF hearing sensitivity, affect OAEs that are originated from more apical cochlear parts in tinnitus ears more than non-tinnitus ears.

Cortical reorganization in recent-onset tinnitus patients by the Heidelberg Model of Music Therapy

Pathophysiology and treatment of tinnitus still are fields of intensive research. The neuroscientifically motivated Heidelberg Model of Music Therapy, previously developed by the German Center for Music Therapy Research, Heidelberg, Germany, was applied to explore its effects on individual distress and on brain structures. This therapy is a compact and fast application of nine consecutive 50-min sessions of individualized therapy implemented over 1 week. Clinical improvement and long-term effects over several years have previously been published. However, the underlying neural basis of the therapy's success has not yet been explored. In the current study, the therapy was applied to acute tinnitus patients (TG) and healthy active controls (AC). Non-treated patients were also included as passive controls (PTC). As predicted, the therapeutic intervention led to a significant decrease of tinnitus-related distress in TG compared to PTC. Before and after the study week, high-resolution MRT scans were obtained for each subject. Assessment by repeated measures design for several groups (Two-Way ANOVA) revealed structural gray matter (GM) increase in TG compared to PTC, comprising clusters in precuneus, medial superior frontal areas, and in the auditory cortex. This pattern was further applied as mask for general GM changes as induced by the therapy week. The therapy-like procedure in AC also elicited similar GM increases in precuneus and frontal regions. Comparison between structural effects in TG vs. AC was calculated within the mask for general GM changes to obtain specific effects in tinnitus patients, yielding GM increase in right Heschl's gyrus, right Rolandic operculum, and medial superior frontal regions. In line with recent findings on the crucial role of the auditory cortex in maintaining tinnitus-related distress, a causative relation between the therapy-related GM alterations in auditory areas and the long-lasting therapy effects can be assumed.

Suppression and facilitation of auditory neurons through coordinated acoustic and midbrain stimulation: investigating a deep brain stimulator for tinnitus

OBJECTIVE

The inferior colliculus (IC) is the primary processing center of auditory information in the midbrain and is one site of tinnitus-related activity. One potential option for suppressing the tinnitus percept is through deep brain stimulation via the auditory midbrain implant (AMI), which is designed for hearing restoration and is already being implanted in deaf patients who also have tinnitus. However, to assess the feasibility of AMI stimulation for tinnitus treatment we first need to characterize the functional connectivity within the IC. Previous studies have suggested modulatory projections from the dorsal cortex of the IC (ICD) to the central nucleus of the IC (ICC), though the functional properties of these projections need to be determined.

APPROACH

In this study, we investigated the effects of electrical stimulation of the ICD on acoustic-driven activity within the ICC in ketamine-anesthetized guinea pigs.

MAIN RESULTS

We observed ICD stimulation induces both suppressive and facilitatory changes across ICC that can occur immediately during stimulation and remain after stimulation. Additionally, ICD stimulation paired with broadband noise stimulation at a specific delay can induce greater suppressive than facilitatory effects, especially when stimulating in more rostral and medial ICD locations.

SIGNIFICANCE

These findings demonstrate that ICD stimulation can induce specific types of plastic changes in ICC activity, which may be relevant for treating tinnitus. By using the AMI with electrode sites positioned with the ICD and the ICC, the modulatory effects of ICD stimulation can be tested directly in tinnitus patients.

Combined Central and Peripheral Stimulation for Treatment of Chronic Tinnitus

Background. Tinnitus is a common untreatable condition that originates from central maladaptive plasticity initiated by peripheral injury. Repetitive transcranial magnetic stimulation (rTMS), direct cochlear low-level laser therapy (LLLT), and acupuncture were tried for tinnitus treatment, but the results of these methods were clinically unsatisfactory. Objective. This study aimed to test the combined effect of the 3 methods targeting both peripheral and central auditory areas as a new therapeutic strategy for tinnitus. Methods. For this, 30 patients were randomized to 3 equal groups receiving 3 different interventions: inhibitory rTMS to the left auditory cortex, LLLT (which includes a combination of direct cochlear LLLT and laser acupuncture) to the affected ear(s), and finally, a combination of rTMS and LLLT. The Tinnitus Handicap Inventory (THI) and Visual Analogue Scale (VAS) were assessed before, immediately after, and at 2 weeks and 4 weeks after 10 consecutive every-other-day sessions for each intervention type. Results. We found that combined stimulation was effective in tinnitus treatment. This effect remained for 4 weeks after the end of the treatment. However, each of rTMS and LLLT alone had no significant effect. Repeated-measures ANOVA showed a significant effect of Time and Time × Intervention interaction for THI and VAS scores. The post hoc t test for different time points per intervention revealed a significant difference between baseline and all postintervention measurements of both THI and VAS for the combination intervention. Conclusion. Combined central rTMS and peripheral LLLT is more beneficial as a new method for management of tinnitus rather than these two used separately.