An update: emerging drugs for tinnitus

Evaluation of tinnitus in patients with Temporomandibular Disorders through Axis II of the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) and the Tinnitus Handicap Inventory (THI)

BACKGROUND

Tinnitus is a quite common and bothersome disorder that results in a perceived sound or noise, without an external origin, often causing notable psychological distress. Some interconnections between tinnitus, bodily pain perception, and psychological well-being were previously reported, thus the relationships between tinnitus and temporomandibular joint (TMJ)-related muscle issues, resulting in somatosensory tinnitus, must be deeply investigated. This study aims to assess the prevalence of tinnitus in patients with temporomandibular disorders (TMD) and to examine the correlation between tinnitus and scales assessing the severity of TMD as well as psychological-related parameters.

MATERIALS AND METHODS

In this cross-sectional study, a total of 37 adults with TMD symptoms were enrolled. Diagnostic data were collected using the Axis II of the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) and the Tinnitus Handicap Inventory (THI) questionnaire. Statistical analysis included descriptive assessments and significance was set at p < .05.

RESULTS

Individuals with tinnitus and TMD reported a significantly higher number of body pain areas, indicating a link between tinnitus and increased bodily pain perception. Tinnitus did not significantly impact TMJ-related functions. Significantly higher levels of psychological distress were observed in individuals with tinnitus, as evidenced by elevated scores in depression, generalised anxiety and somatic symptoms.

CONCLUSION

Tinnitus is a complex condition with significant effects on health and well-being, requiring an interdisciplinary approach for effective evaluation and care. The study provides deep insights into the prevalence of tinnitus in TMD patients, underscoring the need for comprehensive treatment strategies addressing both TMD and tinnitus.

Universal Recommendations on Planning and Performing the Auditory Brainstem Responses (ABR) with a Focus on Mice and Rats

Translational audiology research aims to transfer basic research findings into practical clinical applications. While animal studies provide essential knowledge for translational research, there is an urgent need to improve the reproducibility of data derived from these studies. Sources of variability in animal research can be grouped into three areas: animal, equipment, and experimental. To increase standardization in animal research, we developed universal recommendations for designing and conducting studies using a standard audiological method: auditory brainstem response (ABR). The recommendations are domain-specific and are intended to guide the reader through the issues that are important when applying for ABR approval, preparing for, and conducting ABR experiments. Better experimental standardization, which is the goal of these guidelines, is expected to improve the understanding and interpretation of results, reduce the number of animals used in preclinical studies, and improve the translation of knowledge to the clinic.

Seeking Help for Tinnitus and Satisfaction With Healthcare Providers Including Diagnosis, Clinical Services, and Treatment: A Scoping Review

The objective of this scoping review was to describe the extent and type of evidence related to seeking help for tinnitus and satisfaction with healthcare providers including diagnosis, services and treatments along the clinical pathway. The selection criteria were adults aged 18 and over with tinnitus who sought help and where patient satisfaction with healthcare providers was reported. Online databases MEDLINE (OvidSP), Embase (OvidSP), PsycINFO (OvidSP) and CINAHL plus (EBSCO) were searched for original studies in English. The search had no date limit. Twenty-one records were eligible for data extraction. Studies reported that the most common healthcare providers seen were general practitioners, ear, nose and throat specialists and audiologists. Depression and tinnitus severity were related to an increase in the number of times help was sought and the type of healthcare provider seen may also impact patient satisfaction. The majority of participants were unlikely to receive a referral to a specialist at the initial GP consultation. Although there is limited research in this area, help-seekers for tinnitus were generally dissatisfied and reported negative interactions with healthcare providers. However, once in a specialised tinnitus clinical setting, studies reported that most help-seekers were satisfied and had positive interactions with healthcare providers.

Measuring tinnitus in pharmaceutical clinical trials

This paper reviews methods and considerations for measuring tinnitus in clinical trials designed to evaluate treatment options using investigational medicinal products. Tests applied in tinnitus-related research and clinical practice have their own measurement purposes, advantages, and limitations. If the characteristics of each test method are well understood, the test can be effectively used in clinical trials. For the accuracy of clinical trial results, it is necessary to use a test tool with verified validity, reliability, and sensitivity. If a test tool that is likely to have high variability in the same individual is required in the clinical trial, strategies to increase the reliability of the test, such as repeat measurements, may also be needed. In addition, a test tool that meets the purpose of the clinical trial should be selected. For example, the tinnitus questionnaire is appropriate to assess reactions to tinnitus, and measurements of tinnitus loudness or pitch are appropriate to evaluate the psychoacoustic characteristics of tinnitus. In conclusion, the use of validated test tools that meet the purpose of the trial will help with the accuracy of the clinical trial results.

Hearing loss drug discovery and medicinal chemistry: Current status, challenges, and opportunities

Hearing loss is a severe high unmet need condition affecting more than 1.5 billion people globally. There are no licensed medicines for the prevention, treatment or restoration of hearing. Prosthetic devices, such as hearing aids and cochlear implants, do not restore natural hearing and users struggle with speech in the presence of background noise. Hearing loss drug discovery is immature, and small molecule approaches include repurposing existing drugs, combination therapeutics, late-stage discovery optimisation of known chemotypes for identified molecular targets of interest, phenotypic tissue screening and high-throughput cell-based screening. Hearing loss drug discovery requires the integration of specialist therapeutic area biology and otology clinical expertise. Small molecule drug discovery projects in the global clinical portfolio for hearing loss are here collated and reviewed. An overview is provided of human hearing, inner ear anatomy, inner ear delivery, types of hearing loss and hearing measurement. Small molecule experimental drugs in clinical development for hearing loss are reviewed, including their underpinning biology, discovery strategy and activities, medicinal chemistry, calculated physicochemical properties, pharmacokinetics and clinical trial status. SwissADME BOILED-Egg permeability modelling is applied to the molecules reviewed, and these results are considered. Non-small molecule hearing loss assets in clinical development are briefly noted in this review. Future opportunities in hearing loss drug discovery for human genomics and targeted protein degradation are highlighted.

Alterations in auditory brainstem response distinguish occasional and constant tinnitus

BACKGROUND

The heterogeneity of tinnitus is thought to underlie the lack of objective diagnostic measures.

METHODS

Longitudinal data from 20,349 participants of the Swedish Longitudinal Occupational Survey of Health (SLOSH) cohort from 2008 to 2018 were used to understand the dynamics of transition between occasional and constant tinnitus. The second part of the study included electrophysiological data from 405 participants of the Swedish Tinnitus Outreach Project (STOP) cohort.

RESULTS

We determined that with increasing frequency of the occasional perception of self-reported tinnitus, the odds of reporting constant tinnitus after 2 years increases from 5.62 (95% CI, 4.83–6.55) for previous tinnitus (sometimes) to 29.74 (4.82–6.55) for previous tinnitus (often). When previous tinnitus was reported to be constant, the odds of reporting it as constant after 2 years rose to 603.02 (524.74–692.98), suggesting that once transitioned to constant tinnitus, the likelihood of tinnitus to persist was much greater. Auditory brain stem responses (ABRs) from subjects reporting nontinnitus (controls), occasional tinnitus, and constant tinnitus show that wave V latency increased in constant tinnitus when compared with occasional tinnitus or nontinnitus. The ABR from occasional tinnitus was indistinguishable from that of the nontinnitus controls.

CONCLUSIONS

Our results support the hypothesis that the transition from occasional to constant tinnitus is accompanied by neuronal changes in the midbrain leading to a persisting tinnitus, which is then less likely to remit.

FUNDING

This study was supported by the GENDER-Net Co-Plus Fund (GNP-182), the European Union’s Horizon 2020 grants no. 848261 (Unification of Treatments and Interventions for Tinnitus [UNITI]) and no. 722046 (European School for Interdisciplinary Tinnitus Research [ESIT]).

Multidisciplinary Tinnitus Research: Challenges and Future Directions From the Perspective of Early Stage Researchers

Tinnitus can be a burdensome condition on both individual and societal levels. Many aspects of this condition remain elusive, including its underlying mechanisms, ultimately hindering the development of a cure. Interdisciplinary approaches are required to overcome long-established research challenges. This review summarizes current knowledge in various tinnitus-relevant research fields including tinnitus generating mechanisms, heterogeneity, epidemiology, assessment, and treatment development, in an effort to highlight the main challenges and provide suggestions for future research to overcome them. Four common themes across different areas were identified as future research direction: (1) Further establishment of multicenter and multidisciplinary collaborations; (2) Systematic reviews and syntheses of existing knowledge; (3) Standardization of research methods including tinnitus assessment, data acquisition, and data analysis protocols; (4) The design of studies with large sample sizes and the creation of large tinnitus-specific databases that would allow in-depth exploration of tinnitus heterogeneity.

Development of ebselen for the treatment of sensorineural hearing loss and tinnitus

The global impact of hearing loss and related auditory dysfunction including tinnitus and hyperacusis on human health is significant and growing. A substantial body of literature has found that these hearing diseases and disorders result from significant number of genetic variations and molecular mechanisms. Investigational new drugs have been tested and several approved drugs have been repurposed in clinical trials, but no therapeutics for any auditory related indication have been FDA approved. A unique investigational new drug called ebselen (SPI-1005), that is anti-inflammatory and neuroprotective, has been shown to reduce noise-induced and aminoglycoside-induced hearing loss in animals. Multiple phase 2 clinical trials have demonstrated the safety and efficacy of SPI-1005 treatment in Meniere's disease and acute noise-induced hearing loss. SPI-1005 is currently being tested to prevent and treat tobramycin-induced ototoxicity in cystic fibrosis patients with acute lung infections. This review summarizes the published and presented data involving SPI-1005 and other drugs being tested to prevent or treat sensorineural hearing loss. Additionally, recent clinical data showing the relationship between pure tone audiometry and words-in-noise test results in a Meniere's disease are presented, which may have larger implications for the field of hearing research.

Emerging Topics in the Behavioral Neuroscience of Tinnitus

This volume has highlighted the many recent advances in tinnitus theory, models, diagnostics, therapies, and therapeutics. But tinnitus knowledge is far from complete. In this chapter, contributors to the Behavioral Neuroscience of Tinnitus consider emerging topics and areas of research needed in light of recent findings. New research avenues and methods to explore are discussed. Issues pertaining to current assessment, treatment, and research methods are outlined, along with recommendations on new avenues to explore with research.

Auditory Brainstem Responses (ABR) of Rats during Experimentally Induced Tinnitus: Literature Review

Tinnitus is a subjective phantom sound perceived only by the affected person and a symptom of various auditory and non-auditory conditions. The majority of methods used in clinical and basic research for tinnitus diagnosis are subjective. To better understand tinnitus-associated changes in the auditory system, an objective technique measuring auditory sensitivity-the auditory brainstem responses (ABR)-has been suggested. Therefore, the present review aimed to summarize ABR's features in a rat model during experimentally induced tinnitus. PubMed, Web of Science, Science Direct, and Scopus databanks were searched using Medical Subject Heading (MeSH) terms: auditory brainstem response, tinnitus, rat. The search identified 344 articles, and 36 of them were selected for the full-text analyses. The experimental protocols and results were evaluated, and the gained knowledge was synthesized. A high level of heterogeneity between the studies was found regarding all assessed areas. The most consistent finding of all studies was a reduction in the ABR wave I amplitude following exposure to noise and salicylate. Simultaneously, animals with salicylate-induced but not noise-induced tinnitus had an increased amplitude of wave IV. Furthermore, the present study identified a need to develop a consensus experimental ABR protocol applied in future tinnitus studies using the rat model.

Adapting Personal Therapies Using a Mobile Application for Tinnitus Rehabilitation: A Preliminary Study

OBJECTIVES

To develop a smartphone application providing sound therapy and cognitive behavioral therapy (CBT) for treating tinnitus and performing a proof-of-concept pilot study evaluating its potential efficacy.

METHODS

An interactive smartphone application available on iOS and Android platforms was developed, which provided an 8-week tinnitus-specific CBT and personalized and frequency-matched sound therapy. Included patients presented to our tertiary clinic between 2017 and 2018, while those waitlisted were regarded as controls. Three surveys were administrated: Tinnitus Handicap Inventory (THI), Generalized Anxiety Disorder 7-item (GAD-7), and Perceived Stress Scale (PSS).

RESULTS

A total of 30 patients enrolled in this study consisting of 20 treatment and 10 control patients and mean age was 55.4 ± 11.6 years. Treatment and control patients had similar age, sex, and pre-enrolment GAD and PSS (all P > .05). Baseline THI scores were also similar between treatment and control cohorts (50.1 ± 21.9 vs 62.0 ± 20.7; P = .15). After 8 weeks, though changes in GAD and PSS scores were similar (P > .05), the treatment group reported a significantly greater improvement in THI scores (17.7 ± 15.8 vs 5.3 ± 10.5, P = .04).

CONCLUSIONS

This pilot study demonstrated potentially promising efficacy of a smartphone-based CBT and sound therapy platform for treating tinnitus and encourages future randomized controlled trials on this treatment modality.

Association between Hyperacusis and Tinnitus

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

Relationship between headaches and tinnitus in a Swedish study

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

Avenue for Future Tinnitus Treatments

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

Pharmacotherapy of Tinnitus

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

A study on the epidemiology of tinnitus in the United Kingdom

PURPOSE

Subjective tinnitus is a common symptom with potentially negative impact on quality of life. More research is required to gain a deeper understanding of the disease and its clinical presentation. To estimate the incidence of tinnitus and to describe patient-related characteristics such as lifestyle factors and comorbidities.

PATIENTS AND METHODS

Using the Clinical Practice Research Datalink, we calculated incidence rates of first-time diagnosed tinnitus in an adult population between 2000 and 2016. We stratified incidence rates by sex, age, and year of diagnosis. Additionally, we performed a 1:1 matched case-control study comparing body mass index, lifestyle factors and selected comorbidities between patients with incident tinnitus and tinnitus-free controls.

RESULTS

We identified 109 783 adults with a first-time diagnosis of tinnitus between 2000 and 2016, yielding an overall age-standardized incidence rate of 25.0 new tinnitus cases per 10,000 person-years (95% CI: 24.6-25.5). There was a steady increase in tinnitus incidence throughout the study period. Approximately 80% of tinnitus cases were diagnosed at age 40 years or older. We observed the highest incidence rate in individuals aged 60-69 years (41.2 per 10,000 person-years, 95% CI: 40.7-41.7). Smokers and alcohol drinkers were at lower risk of being diagnosed with tinnitus compared with non-smokers and non-drinkers, respectively. The occurrence of tinnitus was strongly associated with a recent diagnosis of several otological and vestibular disorders as well as head and neck disorders.

CONCLUSION

The present observational study found an increasing incidence of tinnitus over time, emphasizing the continuously growing health burden. The findings on patient characteristics, lifestyle factors, and selected comorbidities contribute to a better understanding of risk factors for tinnitus.

Impact of Temporomandibular Joint Complaints on Tinnitus-Related Distress

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