Muscle Contractions and Auditory Perception in Tinnitus Patients and Nonclinical Subjects

Cervicogenic Somatic Tinnitus: A Narrative Review Exploring Non-otologic Causes

Cervicogenic somatic tinnitus (CST) is a subgroup of somatosensory tinnitus that arises from altered sensory input from the cervical spine due to changes in anatomical and physiological functions. Unlike primary tinnitus, usually caused by auditory system issues, CST is due to somatosensory disruptions from the cervical region. Conditions such as degenerative disc disease, cervical spondylosis, whiplash injuries, and neck muscle stress or spasms are commonly associated with CST. The pathophysiology of CST involves complex interactions between the cervical spine's somatosensory inputs and central auditory pathways, particularly affecting the dorsal cochlear nucleus (DCN) in the brainstem, leading to enhanced excitability and synaptic reorganization, giving rise to tinnitus. Accurate diagnosis and management of CST require a comprehensive approach, including patient history, physical examination, audiological assessments, and imaging studies. Treatment strategies encompass physical therapy, medications, interventional procedures, and complementary therapies, aiming to reduce tinnitus perception, alleviate neck dysfunction, and improve overall quality of life. Emerging therapies, such as neuromodulation and regenerative medicine, show promise in further improving CST management. This multidisciplinary approach highlights the importance of addressing both musculoskeletal and auditory health in the effective treatment of CST.

The Effect of Physical Therapy on Somatosensory Tinnitus

Objective: The objective of this work was to assess the effect of physical therapy in patients with somatosensory tinnitus (ST) and explore the influence of physical therapy on clinical variables obtained before treatment. Methods: A total of 43 patients with ST were randomized to the immediate-start group (n = 20) and delayed-start group (n = 23). All patients received physical therapy for 1 week (seven sessions). Each session lasted 60 min. The Visual Analogue Scale (VAS), Tinnitus Handicap Inventory (THI), and numerical pain rating scale (NPRS) scores were documented at baseline and after treatment (week 1) for all patients. For subjects in the immediate-start group, the THI, VAS, and NPRS scores were measured after therapy (weeks 6, 9, and 12, respectively). Medical history characteristic functional activity scale (HCFA) scores were measured at baseline to assess the association between somatic symptoms and tinnitus. Results: At week 1, VAS, THI, and NPRS scores of patients in the immediate-start group were improved by 1.25 ± 1.59, 11.10 ± 15.10, and 0.95 ± 1.54 points, respectively, and were significantly higher than those in the delayed-start group (p < 0.05). The change in VAS, THI, and NPRS scores in the treatment group was significantly positively correlated with the scores of the HCFA before treatment (r = 0.786, p < 0.001; r = 0.680, p = 0.001; r = 0.796, p < 0.001). There was no significant difference in THI, VAS, and NPRS scores among patients in the immediate-start group between weeks 1, 6, 9, and 12 after treatment (p > 0.05). Conclusions: Although more participants were necessary in the further study, the study implies that physical therapy can reduce physical pain, improve tinnitus symptoms, and quality of life in ST patients without hearing loss, and the short-term curative effect is stable, especially for tinnitus patients with clear somatic symptoms.

Early effects of very early cochlear implant activation on tinnitus

BACKGROUND

Cochlear implantation (CI) has long been the standard of care for patients with severe-to-profound hearing impairment. Yet the benefits of CI extend far beyond speech understanding, with mounting recent literature supporting its role in tinnitus abatement. However, those studies have uniformly analyzed the effects of tinnitus after the traditional 3-4 weeks waiting period between CI surgery and device activation. As many clinics are shifting these waiting intervals to become shorter (in some cases within 24 hours, little is known about tinnitus abatement very early in the postoperative period. The aim of this study was to compare preoperative and postoperative tinnitus handicaps in this unique but growing population of very early-activated patients.

METHODS

Twenty-seven adults with severe-to-profound hearing impairment with chronic tinnitus (>6 months) were included. Patients with concomitant psychiatric disorders were excluded. All patients were implanted with the same array and were switched on within 24 hours after the surgery. Tinnitus Handicap Inventory (THI) was recorded preoperatively, immediately after activation at 24 hours postoperatively, at 1 week, 2 weeks, and I month after activation. Wilcoxon signed-rank test was used to compare values between preoperative assessment and respective fitting sessions.

RESULTS

Mean THI 24 hours after implantation increased in comparison to that assessed preoperatively (77.6 vs 72.5, p = 0.001). By 1 week after surgery, the THI had decreased to 54.9 ( p < 0.001). This trend continued and was statistically significant at 2 weeks (36.0, p < 0.001) and 1 month (28.5, p < 0.001).

CONCLUSION

On average, most patients with tinnitus will note a significant improvement in their tinnitus handicap when activated within 24 hours of CI. However, tinnitus does increase between surgery and 24 hours, most likely reflecting not only intracochlear changes, but modulation of the entire auditory pathway. Following this early rise, the tinnitus continues to abate over the following month. Patients with tinnitus may benefit from early activation, although should be counseled that they may experience an exacerbation during the very early postoperative period.

Pilot study on the role of somatic modulation in hyperacusis

BACKGROUND

Hyperacusis is a reduced tolerance to sounds that often co-occurs with tinnitus. Both symptoms have convergent as well as divergent characteristics. Somatic modulation, changes in pitch or loudness during certain movements, is common in patients with a primary complaint of tinnitus. However, thus far, this is not documented in patients with hyperacusis.

OBJECTIVES

This study aimed to examine the influence of somatic manoeuvres on the perception of external sounds in patients with a primary complaint of hyperacusis.

METHODOLOGY

In this prospective cross-sectional pilot study, 18 patients with a primary complaint of hyperacusis were recruited at the Tinnitus Treatment and Research Center Antwerp (TINTRA). While patients listened to a 1 kHz broadband noise of 30 dB sensation level, six neck manoeuvres (flexion, extension, lateroflexion left/right, traction and compression), three jaw manoeuvres (protrusion, laterotrusion left/right) and one placebo manoeuvre (hand on head) were performed. The primary outcome measure was the change in the perception of the presented sound in terms of loudness and intrusiveness between baseline and each modulation measured by a visual analogue scale (VAS).

RESULTS

No overall significant changes were found; however, individual results indicated that five patients presented a clinically relevant change of more than three points out of ten on VAS in terms of hyperacusis after at least one of the executed somatic manoeuvres.

CONCLUSIONS

This pilot study did not demonstrate an overall significant change in hyperacusis after somatic manoeuvres but does not rule out the possibility of somatic modulation in some hyperacusis patients.

TRIAL REGISTRATION

The protocol of this prospective cross-sectional pilot study was registered on clinicaltrials.gov with registration number NCT04693819.

Occlusal problems: Hearing symptoms in subjects with temporomandibular disorder

OBJECTIVE

This study aimed to investigate the relationship between occlusal problems and hearing symptoms.

METHODS

Electromyography, occlusion analysis, and hearing tests were performed on 24 patients with temporomandibular disorders and concurrent ear symptoms and 16 subjects in the control group.

RESULTS

The null hypothesis of no statistically significant relationship between pure tone audiometry (PTA) values and disclusion times (DT) > 0.40 s and <0.40 s was rejected. There were statistically significant correlations between 0.25, 0.5, 1, 6, and 8 kHz airways of the right and left ear and 1 and 2 kHz bone conduction for disclusion times >0.40 s.

CONCLUSION

Reducing disclusion time to <0.40 s may ameliorate ear symptoms.

Methods, Applications, and Limitations of Somatic Maneuvers for the Modulation of Tinnitus

The modulation of tinnitus through somatic maneuvers is a well-documented phenomenon in tinnitus patients with somatic disorders. The purpose of this study was to review the methods, applications, and limitations of somatic maneuvers. First, 35 somatic maneuvers proposed by various research groups were summarized according to four body areas (jaw, head and neck, eye, and limbs), following which their applications and limitations were assessed. Although some studies have shown that somatic maneuvers can aid in screening for somatic tinnitus and may help alleviate symptoms with repeated practice, the limited number of studies and inconsistent results among studies make it difficult to draw definitive conclusions. Therefore, follow-up studies are required to overcome these limitations and determine whether the treatment of somatic disorders can also aid in alleviating somatic tinnitus.

Anterior Cervical Decompression and Fusion Surgery for Cervical Spondylosis with Concomitant Tinnitus: A Multicenter Prospective Cohort Study

OBJECTIVE

Cervical spondylosis is often accompanied by tinnitus. Up to now, there is a lack of large samples and prospective studies to investigate the effect of anterior cervical decompression and fusion (ACDF) on tinnitus associate with cervical spondylosis. To this end, we performed a prospective cohort study to assess the effectiveness of ACDF on the relief of tinnitus.

METHODS

This was a multicenter, prospective, cohort clinical study. Between August 2017 and August 2018, 174 patients with cervical spondylosis accompanied by tinnitus were enrolled, with a follow-up of 12 months. Among the 174 patients, 142 received anterior cervical surgery (surgery group) and 32 received conservative treatment (conservative group). The primary end point was the mean change in scores on the tinnitus functional index (TFI). The secondary end points included tinnitus loudness, modified Japanese orthopaedic association scores (mJOA) for spinal cord function, and visual analogue scale (VAS) for neck pain. All the above indexes were measured before treatments and at 1, 3, 6, and 12 months after treatments. One-way analysis of variance and paired samples t-test was adopted for statistical analysis.

RESULTS

The TFI score was reduced immediately after cervical decompression surgery (from 54.7 ± 15.6 to 32.3 ± 12.5, P < 0.001) and this was sustained at 12 months (P < 0.001). The TFI score of the conservative group also decreased (from 53.9 ± 16.8 to 45.2 ± 13.6, P < 0.001), but the effect was not maintained at 12 months (P = 0.069). There was a significant improvement in tinnitus loudness (from 5.2 ± 1.6 to 2.6 ± 1.9, P < 0.001), mJOA (from 12.0 ± 1.6 to 14.2 ± 1.6, P < 0.001), and VAS for neck pain (from 58.5 ± 9.6 to 22.0 ± 16.4, P < 0.001) in the surgical group. Improvements in the surgical group were statistically significantly greater than that in the conservative group (P < 0.001).

CONCLUSION

This study indicates that anterior cervical surgery can relieve tinnitus in patients with cervical spondylosis and that tinnitus is an accompanying manifestation of cervical spondylosis.

Prevalence of Somatosensory Tinnitus in Veterans With Tinnitus

OBJECTIVES

The primary objective was to estimate the prevalence of somatosensory tinnitus (ST) among Veterans with tinnitus.

DESIGN

Three hundred four Veterans with tinnitus were phone screened for ST by performing and reporting on a series of head/neck/jaw maneuvers. A random sample of 12 individuals who screened positive and five who screened negative attended an in-person visit to confirm the presence/absence of ST.

RESULTS

Of the 304 Veterans, 12 could not complete the screening maneuvers, 205 screened positive, and 87 screened negative. A Bayesian estimator that combines phone screening and in-person exam results establishes the prevalence of ST among Veterans with tinnitus at 56% with a 90% Bayesian confidence interval of 45% to 65%.

CONCLUSIONS

At least half of Veterans with tinnitus have ST, suggesting that a sizable at-need population exists. Treatment addressing the biomechanical component has the potential to improve tinnitus symptoms.

Somatosensory Tinnitus Diagnosis: Diagnostic Value of Existing Criteria

BACKGROUND

Tinnitus can be influenced by changes in somatosensory afference from the cervical spine or temporomandibular area, then called somatosensory or somatic tinnitus (ST). In 2018, a new set of diagnostic criteria for ST was agreed upon by a large group of ST experts. Currently, however, it still requires extensive and specific expertise to diagnose ST correctly. The next step in the development of easily applicable diagnostic criteria is to assess the diagnostic value of each individual criterion.

OBJECTIVES

The aim of this study was, therefore, to further investigate the diagnostic value of these criteria, validate them empirically, and identify their sensitivity and specificity.

METHODS

An online survey, questioning the presence of 12 diagnostic criteria for ST in a convenience sample of participants with tinnitus, was launched on the online forum Tinnitus Talk, managed by Tinnitus Hub. Participants were divided into three groups: a group with no somatic influence, a group with some somatic influence and a group with large somatic influence on their tinnitus. Chi-square tests were used to calculate differences between these groups. Afterward, sensitivity, specificity, positive and negative likelihood ratios (LR), and pre- and posttest probabilities were calculated for each ST diagnostic criterion. For this analysis, all patients with some and large somatic influence were compared as one group to the group with no somatic influence.

RESULTS

In total, 8221 participants filled out the online survey. As expected, the diagnostic criteria for ST are more prevalent in the groups with somatic influence, but the criterium of tinnitus modulation also often occurs in the group with no somatic influence. The simultaneous onset or increase and decrease of both tinnitus and pain complaints have the highest positive LR (6.29 and 10.72, respectively), next to the influence of certain postures on the tinnitus (+LR: 6.04). To rule out ST, the absence of neck pain or tension in the neck extensor muscles are most suited, as they decrease the posttest probability to 18% and 19%, respectively.

CONCLUSION

The simultaneous onset or increase and decrease of tinnitus and neck or jaw pain and the influence of certain postures are most suited to use as a single criterion for identifying patients with a somatic influence on their tinnitus. On the other hand, the absence of neck pain or tension in the neck extensor muscles is valid criterion to rule out a somatic influence. Additional analysis is needed to identify clusters of symptoms and criteria to further aid ST diagnosis.

Somatic Modulation in Tinnitus: Clinical Characteristics and Treatment Outcomes

OBJECTIVES

We aimed to evaluate the clinical significance of the somatic modulation test in patients with tinnitus and analyze the treatment outcomes.

MATERIALS AND METHODS

Medical records of patients who visited the tinnitus clinic at a local university hospital between October 2018 and April 2019 were retrospectively reviewed.

RESULTS

The data of 81 patients were analyzed for this study, of which 61.7% (n=51) showed tinnitus modulation after one or more neck or jaw maneuvers. Patients with narrow-band noise tinnitus tended to show maneuver-induced modulation more frequently than those with pure-tone tinnitus (85.7% vs. 53.3%, p=0.010). Neck maneuvers reduced tinnitus loudness in 29.6% of the patients, while 27.2% of patients (n=22) reported worsening of tinnitus loudness, and 23.5% of patients (n=19) reported tinnitus suppression after jaw maneuvers. None of the patients with noise exposure history reported tinnitus modulation. Backward regression analysis revealed that age was an independent risk factor for improvement (Exp [B]=0.703, p=0.034, 95% CI=0.508-0.974). However, somatic modulation or medical treatments targeting somatic modulation were not related to improvement.

CONCLUSION

Patients showing modulation after neck or jaw maneuvers have specific clinical characteristics. However, somatic modulation itself does not affect the final treatment outcome.

Tinnitus Neuroimaging

This article reviews the use of human neuroimaging for chronic subjective tinnitus. Evidence-based guidance on the clinical use of imaging to identify relevant auditory lesions when evaluating tinnitus patients is given. After introducing the anatomy and imaging modalities most pertinent to the neuroscience of tinnitus, the article reviews tinnitus-associated alterations in key auditory and nonauditory networks in the central nervous system. Emphasis is placed on how these findings support proposed models of tinnitus and how this line of investigation is relevant to practicing clinicians.

Physiotherapy assessment and treatment of chronic subjective tinnitus using mechanical diagnosis and therapy: a case report

Objectives: Tinnitus is the perception of sound without any external auditory stimulus. Cervicogenic somatic tinnitus (CST) is a subset in which symptoms are modulated by maneuvers of the neck. The evidence for effective diagnosis and treatment of CST is limited. Mechanical Diagnosis and Therapy (MDT) is a biopsychosocial assessment and management system that uses the response to mechanical forces to classify clinical presentations accurately. The purpose of this case report is to describe the MDT assessment and management of a patient with chronic subjective tinnitus.Methods: A 67-year-old female with a 5-year history of left-sided subjective tinnitus, neck pain, and headache was referred for physiotherapy. Outcome measures included the Visual Analogue Scale (VAS), Tinnitus Handicap Inventory (THI), and Neck Disability Index (NDI). She was evaluated and treated according to MDT principles with management consisting of individualized directional preference exercises and postural correction.Results: Significant improvements in symptoms, cervical range of motion, function, and psychosocial status were observed over the long-term. At 6 months, THI scores dropped from 62/100 to 18/100 and NDI scores dropped from 18/50 to 3/50.Discussion: A comprehensive MDT assessment led to a classification of Derangement, with treatment focusing on tailored self-management. Contrary to other interventions described for CST, the patient was able to make significant and lasting changes to her symptoms without the need for any externally applied interventions. The emphasis on self-management dovetails well with the biopsychosocial model of care. This case provides preliminary evidence for the utility of screening for Derangement in conservative tinnitus assessments.Level of Evidence: 4.

Test-Retest Reproducibility of Response Duration in Tinnitus Patients With Positive Residual Inhibition

Purpose Functional imaging is often used to try to elucidate the pathophysiological mechanism of tinnitus. Residual inhibition, the temporary suppression of tinnitus after application of a masking noise, could be an interesting technique to modulate tinnitus perception in functional imaging paradigms. The purposes of this study were to primarily assess reproducibility of the (partial) positive residual inhibition response duration in patients with tinnitus and to explore its utility in experimental designs. Method Patients with tinnitus exhibiting a (partial) positive residual inhibition response or tinnitus reduction after a 1-min white noise presentation were selected from a broad consulting tinnitus population. In 27 patients, this response was tested 4 times: twice during initial testing and twice during a retest of the psychoacoustic tinnitus measures, 4-8 weeks after initial consultation. In 17 patients with stable residual inhibition responses, reproducibility of response duration, the duration of tinnitus reduction up to pretesting state, was analyzed. Results Initial testing showed a residual inhibition duration of 29.5 s on average. Test-retest reproducibility of response duration was shown to be reliable with an ICC(3, 4) of .871 (95% CI [0.733, 0.948]) and a standard error of measurement of 6.64 s. Conclusions This study indicates the good test-retest reproducibility of residual inhibition duration in our subset of 17 patients with stable (partial) positive residual inhibition. Residual inhibition is, therefore, a technique that can potentially be used for temporary tinnitus manipulation in experimental paradigms to unravel tinnitus pathophysiology.

The Presence of Physical Symptoms in Patients With Tinnitus: International Web-Based Survey

Background

Tinnitus, or ringing in the ears, is a phantom perception of sound in the absence of overt acoustic stimulation. Many patients indicate that the perception of their tinnitus is not constant and can vary from moment to moment. This tinnitus fluctuation is one of the diagnostic criteria for somatosensory tinnitus (ST), a tinnitus subtype that is influenced by cervical spine or temporomandibular dysfunctions, although various factors have been reported to cause fluctuations in tinnitus, such as stress, anxiety, and physical activity.

Objective

The aim of this study was twofold: (1) to investigate the presence of physical symptoms in a large group of participants with tinnitus and (2) to investigate if these physical symptoms are more frequently present in a subgroup of participants with ST.

Methods

A Web-based survey, questioning the presence of physical symptoms in a convenience sample of participants with tinnitus, was launched on the online forum, Tinnitus Talk, managed by Tinnitus Hub. After a general analysis of the physical symptoms present in our survey population, we further analyzed the group of participants who were diagnosed by a physician (n=1262). This subgroup was divided into 2 groups, one group diagnosed with ST and another group diagnosed with other types of tinnitus.

Results

In total, 6115 participants with a mean age of 54.08 years (SD 13.8) completed the survey. Physical symptoms were frequently present in our sample of participants with tinnitus: 4221 participants (69.02%) reported some form of neck pain, 429 (7.01%) were diagnosed with temporomandibular disorders, 2730 (44.64%) indicated they have bruxism, and between 858 and 1419 (14.03%-23.20%) participants were able to modulate their tinnitus by voluntary movements. ST was diagnosed in 154 out of 1262 (12.20%) participants whose tinnitus cause was diagnosed by a physician. Symptoms referring to the known diagnostic criteria were evidently more present in the ST group than in the non-ST group. Additionally, participants with ST more often indicated a negative effect of a bad night’s sleep (P=.01) and light intensity exercise (P=.01).

Conclusions

Physical activity and movement (disorders) frequently affect tinnitus severity. Head-neck related symptoms are more frequently reported in the ST group, as is the ability to modulate the tinnitus by head or jaw movements. Additionally, participants with ST more often report fluctuations of their tinnitus and reaction to sleeping difficulties and low intensity exercise.

The Role of the Brainstem in Generating and Modulating Tinnitus

Purpose The purpose of this work is to present a perspective article summarizing ideas pertaining to the brainstem's role in generating and modulating tinnitus. It is organized in 4 sections: Part 1, the role of the brainstem as a tinnitus generator; Part 2, the role of the brainstem in modulating tinnitus; Part 3, the role of the brainstem in nonauditory comorbid conditions associated with tinnitus; and Part 4, clinical implications. In Part 1, well-established neurophysiological models are discussed providing the framework of evidence that auditory brainstem nuclei play a role in generating tinnitus. In Part 2, ideas are presented explaining modulatory effects on tinnitus related to underlying pathways originating from or projecting to brainstem auditory and nonauditory nuclei. This section addresses multiple phenomena including somatic-related, attention-mediated, and emotion-mediated changes in the tinnitus percept. In Part 3, the role of the brainstem in common nonauditory comorbidities that occur in patients with tinnitus is discussed. Part 4 presents clinical implications of these new ideas related to the brainstem's involvement in generating and modulating tinnitus. Impact Knowledge of the brainstem's involvement in generating and modulating tinnitus provides a context for health care professionals to understand the temporal relationship between tinnitus and common nonauditory comorbid conditions.

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

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

Diagnostic Criteria for Somatosensory Tinnitus: A Delphi Process and Face-to-Face Meeting to Establish Consensus

Since somatic or somatosensory tinnitus (ST) was first described as a subtype of subjective tinnitus, where altered somatosensory afference from the cervical spine or temporomandibular area causes or changes a patient’s tinnitus perception, several studies in humans and animals have provided a neurophysiological explanation for this type of tinnitus. Due to a lack of unambiguous clinical tests, many authors and clinicians use their own criteria for diagnosing ST. This resulted in large differences in prevalence figures in different studies and limits the comparison of clinical trials on ST treatment. This study aimed to reach an international consensus on diagnostic criteria for ST among experts, scientists and clinicians using a Delphi survey and face-to-face consensus meeting strategy. Following recommended procedures to gain expert consensus, a two-round Delphi survey was delivered online, followed by an in-person consensus meeting. Experts agreed upon a set of criteria that strongly suggest ST. These criteria comprise items on somatosensory modulation, specific tinnitus characteristics, and symptoms that can accompany the tinnitus. None of these criteria have to be present in every single patient with ST, but in case they are present, they strongly suggest the presence of ST. Because of the international nature of the survey, we expect these criteria to gain wide acceptance in the research field and to serve as a guideline for clinicians across all disciplines. Criteria developed in this consensus paper should now allow further investigation of the extent of somatosensory influence in individual tinnitus patients and tinnitus populations.

Conservative therapy for the treatment of patients with somatic tinnitus attributed to temporomandibular dysfunction: study protocol of a randomised controlled trial

BACKGROUND

Tinnitus is a highly prevalent symptom affecting 10-15% of the adult population. It often affects patient quality of life and frequently causes distress. When subjective tinnitus can be elicited by the somatosensory system of the cervical spine or temporomandibular area it is termed somatic tinnitus. The first aim of the current study is to investigate the effect of the best evidence conservative temporomandibular disorder (TMD) treatment on tinnitus in patients with co-existence of tinnitus and TMD or oral parafunctions compared to no treatment. The second aim is to identify a subgroup of patients with tinnitus that benefits from the conservative temporomandibular joint treatment.

METHODS AND DESIGN

This study is a randomised controlled trial with a delayed treatment design. Patients with a TMD (TMD pain screener ≥ 3 points) or oral parafunctions (such as clenching and bruxism), who are suffering from moderate to severe subjective tinnitus (Tinnitus Functional Index (TFI) between 25 and 90 points), will be recruited from the tertiary tinnitus clinic of the University Hospital of Antwerp, Edegem, Belgium. Patients will be excluded in case of clear otological or neurological causes of the tinnitus, progressive middle ear pathology, intracranial pathology, traumatic cervical spine or temporomandibular injury in the past 6 months, severe depression as diagnosed by a psychologist, tumours, previous surgery in the orofacial area, substance abuse that may affect the outcome measures, any contra-indication for physical therapy treatment directed to the orofacial area or when they received TMD treatment in the past 2 months. After screening for eligibility, baseline data among which scores on the TFI, tinnitus questionnaire (TQ), mean tinnitus loudness as measured with visual analogue scale (VAS), TMD pain screener, and a set of temporomandibular joint tests will be collected. Patients will be randomised in an early-start group and in a delayed-start group of therapy by 9 weeks. Patients will receive conservative TMD treatment with a maximum of 18 sessions within 9 weeks. At baseline (week 0), at the start of therapy (weeks 0 or 9), 9 weeks after therapy (weeks 9 or 18), and at follow-up (weeks 18 or 27) data from the TFI, TQ, VAS mean tinnitus loudness and the TMD pain screener will be collected.

DISCUSSION

Herein, we aim to improve the quality of care for patients with tinnitus attributed to TMD or oral parafunctions. By evaluating the effect of state-of-the-art TMD treatment on tinnitus complaints, we can investigate the usefulness of TMD treatment in patients with somatic tinnitus.

TRIAL REGISTRATION

3 July 2017, version 1 of the protocol, ClinicalTrials.gov NCT03209297 .

Subtyping patients with somatic tinnitus: Modulation of tinnitus and history for somatic dysfunction help identify tinnitus patients with temporomandibular joint disorders

OBJECTIVE

Determine in a cohort of patients with normal hearing and chronic tinnitus if self-reported history for temporomandibular joint (TMJ) dysfunction and a positive modulation of tinnitus in the TMJ region could be suggestive of an underlying TMJ disorder.

PATIENTS AND METHODS

The study included 226 patients presenting to the Head and Neck Service of our University Hospital. Following audiological and somatic tinnitus evaluation, patients were divided into two groups. The study group (n = 134) included subjects that met both the following criteria: A) a self-reported history for TMJ dysfunction and B) a positive modulation of tinnitus following somatic maneuvers in the TMJ region. The control group (n = 92) included patients with similar demographic and tinnitus characteristics that did not meet the proposed criteria for somatic tinnitus. Afterwards, patients underwent clinical TMJ evaluation in the Service of Clinical Gnathology of our University.

RESULTS

One hundred thirty-one patients (57.9%) received a clinical diagnosis of TMJ disorder according to DC/TMD Axis I; 79.1% in the study group and 27.2% in the control group. Ninety-five (42.1%) patients were negative for TMJ disorders; 20.9% in the study group and 72.8% in the control group. A significantly higher number of TMJ disorders was found in patients in the study group compared to the control group (p<0.0001). Most patients had joint disorders (67.2%), followed by other (29.8%) and pain disorders (29%). Logistic regression analysis in the study group showed that female gender was more prevalent in patients with TMJ disorders.

CONCLUSION

Our findings in patients with chronic tinnitus and normal hearing suggest that self-reported history for somatic dysfunction and modulation of tinnitus, when occurring simultaneously in the TMJ region, can be useful to preliminarily identify patients with TMJ disorders.

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.

Somatosensory tinnitus: Current evidence and future perspectives

In some individuals, tinnitus can be modulated by specific maneuvers of the temporomandibular joint, head and neck, eyes, and limbs. Neuroplasticity seems to play a central role in this capacity for modulation, suggesting that abnormal interactions between the sensory modalities, sensorimotor systems, and neurocognitive and neuroemotional networks may contribute to the development of somatosensory tinnitus. Current evidence supports a link between somatic disorders and higher modulation of tinnitus, especially in patients with a normal hearing threshold. Patients with tinnitus who have somatic disorders seems to have a higher chance of modulating their tinnitus with somatic maneuvers; consistent improvements in tinnitus symptoms have been observed in patients with temporomandibular joint disease following targeted therapy for temporomandibular disorders. Somatosensory tinnitus is often overlooked by otolaryngologists and not fully investigated during the diagnostic process. Somatic disorders, when identified and treated, can be a valid therapeutic target for tinnitus; however, somatic screening of subjects for somatosensory tinnitus is imperative for correct selection of patients who would benefit from a multidisciplinary somatic approach.

Is Electroacupuncture Treatment More Effective in Somatic Tinnitus Than in Nonsomatic Tinnitus?

Background: In recent years, evidence has been accumulating linking subjective tinnitus to the somatosensory system. Somatic tinnitus is defined as tinnitus in which forceful contractions of jaw and neck muscles modulate the psychoacoustic attributes of tinnitus, such as pitch and loudness. Being a somatosensory-based treatment modality, needling might well be more effective for treating somatic than nonsomatic tinnitus. Objective: The aim of this study was to compare the outcomes of electroacupuncture (EA) treatment between patients with somatic and nonsomatic tinnitus. Materials and Methods: A single-blinded prospective study was carried wherein 27 patients with tinnitus were divided into either a somatic or a nonsomatic group, based on whether their tinnitus could be modulated by at least one of a series of forceful jaw and neck muscular contraction maneuvers. Tinnitus responses were evaluated after a single session of EA on selected acupoints for 30 minutes. Results: Seventeen of the 27 patients (63.0%) studied were found to have somatic tinnitus. Generalized estimating equation model analysis did not find any overall statistically significant difference in EA response between patients with somatic and nonsomatic tinnitus. However, patients with somatic tinnitus who were consistent in their responses to the muscular contraction maneuvers were more likely to improve with EA than variable responders to these maneuvers (62.5% versus 22.0%). Conclusions: EA did not provide increased benefits for patients with somatic tinnitus, compared to those with nonsomatic tinnitus overall. However, within the somatic tinnitus group, a subpopulation of patients appeared to be relatively more responsive to EA treatment.

Pathophysiology, Diagnosis and Treatment of Somatosensory Tinnitus: A Scoping Review

Somatosensory tinnitus is a generally agreed subtype of tinnitus that is associated with activation of the somatosensory, somatomotor, and visual-motor systems. A key characteristic of somatosensory tinnitus is that is modulated by physical contact or movement. Although it seems common, its pathophysiology, assessment and treatment are not well defined. We present a scoping review on the pathophysiology, diagnosis, and treatment of somatosensory tinnitus, and identify priority directions for further research. Methods: Literature searches were conducted in Google Scholar, PubMed, and EMBASE databases. Additional broad hand searches were conducted with the additional terms etiology, diagnose, treatment. Results: Most evidence on the pathophysiology of somatosensory tinnitus suggests that somatic modulations are the result of altered or cross-modal synaptic activity within the dorsal cochlear nucleus or between the auditory nervous system and other sensory subsystems of central nervous system (e.g., visual or tactile). Presentations of somatosensory tinnitus are varied and evidence for the various approaches to treatment promising but limited. Discussion and Conclusions: Despite the apparent prevalence of somatosensory tinnitus its underlying neural processes are still not well understood. Necessary involvement of multidisciplinary teams in its diagnosis and treatment has led to a large heterogeneity of approaches whereby tinnitus improvement is often only a secondary effect. Hence there are no evidence-based clinical guidelines, and patient care is empirical rather than research-evidence-based. Somatic testing should receive further attention considering the breath of evidence on the ability of patients to modulate their tinnitus through manouvers. Specific questions for further research and review are indicated.

The Effect of Physical Therapy Treatment in Patients with Subjective Tinnitus: A Systematic Review

Background: Tinnitus is a very common symptom that often causes distress and decreases the patient's quality of life. Apart from the well-known causes, tinnitus can in some cases be elicited by dysfunctions of the cervical spine or the temporomandibular joint (TMJ). To date however, it is unclear whether alleviation of these dysfunctions, by physical therapy treatment, also decreases the tinnitus complaints. Such physical therapy could be an interesting treatment option for patients that are now often left without treatment.

Objectives: The aim of this review was to investigate the current evidence regarding physical therapy treatment in patients with tinnitus.

Data sources: The online databases Pubmed, Web of Science, Cochrane, and Embase were searched up to March 2016. Two independent reviewers conducted the data extraction and methodological quality assessment.

Study eligibility criteria: Only randomized controlled trials and quasi-experimental trials were included in the review. Studies had to be written in English, French, Dutch, or German.

Participants and interventions: The included studies investigated the effect of physical therapy treatment modalities on tinnitus severity in patients suffering from subjective tinnitus.

Results: Six studies were included in this review, four investigating cervical spine treatment and two investigating TMJ treatment. These studies show positive effects of cervical spine treatment (manipulations, exercises, triggerpoint treatment) on tinnitus severity. Additionally, decrease in tinnitus severity and intensity was demonstrated after TMJ treatment, following splints, occlusal adjustments as well as jaw exercises.

Limitations: The risk of bias in the included studies was high, mainly due to lack of randomization, lack of blinding of subjects, therapists, and/or investigators. Additionally, risk of bias is present due to incomplete presentation of the data and selective reporting. A major issue of the reviewed papers is the heterogeneity of the included study populations, treatments and outcome measures, which inhibit data pooling and meta-analysis.

Conclusions: Despite the methodological issues in the included studies and the consequent low quality evidence, it is noteworthy that all included studies show positive treatment effects. Before recommendations can be made, these results need to be confirmed in larger, high quality studies, using unambiguous inclusion criteria, state-of-the-art treatment, and high quality outcome measures.

Somatic Modulation of Tinnitus: Test Reliability and Results after Repetitive Muscle Contraction Training

Objectives:

We sought to study the reliability of tinnitus modulation by muscle contractions and to observe the effect of their prolonged repetition.

Methods:

Thirty-eight patients with tinnitus underwent 9 maneuvers of muscle contractions in test and retest situations. After a 2-month training period of repeating the maneuvers, tinnitus modulation and daily perception were evaluated.

Results:

There was no difference between the occurrence of tinnitus modulation in test (57.9%) and retest (63.2%) situations. After 2 months, the occurrence of modulation during the maneuvers was similar (55.3%), but a new pattern showed an increase in tinnitus improvement and a decrease in tinnitus worsening. The daily perception of tinnitus was unchanged.

Conclusions:

Maneuvers of head and neck muscle contractions evoked tinnitus modulation in a frequent and reliable manner. Also, the repetition of such maneuvers for 2 months altered the pattern of modulation.

Diagnostic Value of Clinical Cervical Spine Tests in Patients With Cervicogenic Somatic Tinnitus

BACKGROUND

Tinnitus can be related to many different etiologies, such as hearing loss or a noise trauma, but it also can be related to the somatosensory system of the cervical spine. The diagnosis of cervicogenic somatic tinnitus (CST) is made when the predominant feature is the temporal coincidence of appearance or increase of both neck pain and tinnitus.

OBJECTIVE

The aim of this study was to assess the diagnostic value of clinical cervical spine tests in people with CST.

DESIGN

A cross-sectional study was conducted.

SETTING

The study was conducted at a tertiary referral center.

PATIENTS

Consecutive adult patients with chronic subjective nonpulsatile tinnitus were included. Exclusion criteria were vertigo, Ménière disease, middle ear pathology, intracranial pathology, cervical spine surgery, whiplash trauma, and temporomandibular dysfunction.

MEASUREMENTS

A full ear, nose, and throat examination was conducted to classify patients into CST and non-CST groups. The physical therapist examination included completion of the Neck Bournemouth Questionnaire (NBQ) and the following clinical cervical spine tests: manual rotation test, adapted Spurling test (AST), trigger point tests, and tests for strength and endurance of the deep neck flexors.

RESULTS

Eighty-seven patients with tinnitus were included, of whom 37 (43%) were diagnosed with CST. The diagnosis of CST becomes less likely with NBQ scores of <14 points (sensitivity of 80%, likelihood ratio [LR] of 0.3, and posttest probability of 19%). Absence of trigger points corresponded to an LR of 0.3, a sensitivity of 82%, and a posttest probability of 22%. A positive manual rotation test and AST indicate a higher probability of CST (LR of 5, specificity of 90%, and posttest probability of 78%).

LIMITATIONS

A limited number of clinical cervical spine tests were used in this study. Although tests with good validity and reliability were included, additional tests could provide more information on cervical spine dysfunction in patients with CST.

CONCLUSIONS

Clinical cervical spine tests can support the diagnostic process for CST. An NBQ score of <14 points and the absence of trigger points can help to exclude CST. In contrast, a positive manual rotation test and AST can help to include CST. In future studies, these tests should be included in a multidisciplinary assessment of patients with suspected CST.

Cervical spine dysfunctions in patients with chronic subjective tinnitus

OBJECTIVE

To assess, characterize, and quantify cervical spine dysfunction in patients with cervicogenic somatic tinnitus (CST) compared to patients suffering from other forms of chronic subjective non-pulsatile tinnitus.

STUDY DESIGN

Cross-sectional study.

SETTING

Tertiary referral center.

PATIENTS

Consecutive adult patients suffering from chronic subjective non-pulsatile tinnitus were included.

EXCLUSION CRITERIA

Ménière's disease, middle ear pathology, intracranial pathology, cervical spine surgery, whiplash trauma, temporomandibular dysfunction.

INTERVENTION

Assessment comprises medical history, ENT examination with micro-otoscopy, audiometry, tinnitus assessment, temporomandibular and cervical spine investigation, and brain MRI. Patients were classified into CST and non-CST population. Cervical spine dysfunction was investigated using the Neck Bournemouth Questionnaire (NBQ) and clinical tests of the cervical spine, containing range of motion, pain provocation (adapted Spurling test, AST), and muscle tests (tenderness via trigger points, strength and endurance of deep neck flexors).

MAIN OUTCOME MEASURES

Between-group analysis was performed. The prevalence of cervical spine dysfunction was described for the total group and for CST and non-CST groups.

RESULTS

In total, 87 patients were included, of which 37 (43%) were diagnosed with CST. In comparison with the non-CST group, the CST group demonstrated a significantly higher prevalence of cervical spine dysfunction. In the CST group, 68% had a positive manual rotation test, 47% a positive AST, 49% a positive score on both, and 81% had positive trigger points. In the non-CST group, these percentages were 36, 18, 10, and 50%, respectively. Furthermore, 79% of the CST group had a positive NBQ versus 40% in the non-CST group. Significant differences between the both groups were found for all the aforementioned variables (all p < 0.005).

CONCLUSIONS

Although a higher prevalence of neck dysfunction was found in the CST group, neck dysfunction is often in non-CST patients.

Subtyping Somatic Tinnitus: A Cross-Sectional UK Cohort Study of Demographic, Clinical and Audiological Characteristics

Somatic tinnitus is the ability to modulate the psychoacoustic features of tinnitus by somatic manoeuvres. The condition is still not fully understood and further identification of this subtype is essential, particularly for the purpose of establishing protocols for both its diagnosis and treatment. This study aimed to investigate the characteristics of somatic tinnitus within a large UK cohort using a largely unselected sample. We believe this to be relatively unique in comparison to current literature on the topic. This was investigated by using a total of 608 participant assessments from a set of recognised tinnitus and audiology measures. Results from a set of chi-square tests of association found that amongst the individuals with somatic tinnitus, a higher proportion had pulsatile tinnitus (different from heartbeat), were under the age of 40, reported variation in the loudness of their tinnitus and reported temporomandibular joint (TMJ) disorder. The same pattern of results was confirmed using a multivariate analysis of the data based on logistic regression. These findings have strong implications towards the profiling of somatic tinnitus as a distinct subtype of general tinnitus.

Tinnitus

Tinnitus, the perception of sound in the absence of an external sound, usually results from a disorder of: (1) the auditory system (usually peripheral, rarely central); (2) the somatosensory system (head and neck); or (3) a combination of the two. Its cause can be determined through its characteristics. The history must include the tinnitus': (1) quality (including whether it can ever be pulsatile or have a clicking component); (2) location; (3) variability; (4) predominant pitch (low or high); and (5) whether the patient can do something to modulate the percept. In addition to the standard neuro-otologic examination, the exam should include inspection of the teeth for evidence of wear, listening around the ear and neck for sounds similar to the tinnitus, palpation of the craniocervical musculature for trigger points, and probing whether the tinnitus percept can be modulated with "somatic testing." All subjects should have a recent audiogram. Presently the most compelling tinnitus theory is the dorsal cochlear nucleus (DCN) hypothesis: both the auditory and somatosensory systems converge upon and interact within the DCN. If the activity of the DCN's somatosensory-interacting fusiform cells exceeds an individual's tinnitus threshold, then tinnitus results.

Central gain control in tinnitus and hyperacusis

Sensorineural hearing loss induced by noise or ototoxic drug exposure reduces the neural activity transmitted from the cochlea to the central auditory system. Despite a reduced cochlear output, neural activity from more central auditory structures is paradoxically enhanced at suprathreshold intensities. This compensatory increase in the central auditory activity in response to the loss of sensory input is referred to as central gain enhancement. Enhanced central gain is hypothesized to be a potential mechanism that gives rise to hyperacusis and tinnitus, two debilitating auditory perceptual disorders that afflict millions of individuals. This review will examine the evidence for gain enhancement in the central auditory system in response to cochlear damage. Further, it will address the potential cellular and molecular mechanisms underlying this enhancement and discuss the contribution of central gain enhancement to tinnitus and hyperacusis. Current evidence suggests that multiple mechanisms with distinct temporal and spectral profiles are likely to contribute to central gain enhancement. Dissecting the contributions of these different mechanisms at different levels of the central auditory system is essential for elucidating the role of central gain enhancement in tinnitus and hyperacusis and, most importantly, the development of novel treatments for these disorders.

Differential auditory-oculomotor interactions in patients with right vs. left sided subjective tinnitus: a saccade study

Subjective tinnitus (ST) is a frequent but poorly understood medical condition. Recent studies demonstrated abnormalities in several types of eye movements (smooth pursuit, optokinetic nystagmus, fixation, and vergence) in ST patients. The present study investigates horizontal and vertical saccades in patients with tinnitus lateralized predominantly to the left or to the right side. Compared to left sided ST, tinnitus perceived on the right side impaired almost all the parameters of saccades (latency, amplitude, velocity, etc.) and noticeably the upward saccades. Relative to controls, saccades from both groups were more dysmetric and were characterized by increased saccade disconjugacy (i.e., poor binocular coordination). Although the precise mechanisms linking ST and saccadic control remain unexplained, these data suggest that ST can lead to detrimental auditory, visuomotor, and perhaps vestibular interactions.

Deep Brain Stimulation in Area LC Controllably Triggers Auditory Phantom Percepts

BACKGROUND:

Tinnitus is predominantly viewed as the consequence of dysfunctional hyperactivity, plastic change, or synchronized oscillations in the central auditory system. An alternative to the current auditory-centric view of auditory phantom perception is the basal ganglia-centric view. Recent electrical stimulation experiments in area LC, a locus of the caudate nucleus positioned at its anterior body, has shown loudness modulation of existing tinnitus percepts.

OBJECTIVE:

To demonstrate that auditory phantoms are gated by the dorsal striatum.

METHODS:

Electrical stimulation in area LC via a deep brain stimulation lead was performed in 6 interactive adult subjects (3 with and 3 without chronic tinnitus) undergoing surgery to treat movement disorders. Tinnitus loudness was rated on a 0 to 10 scale, sound quality was described, and localization was referenced to 1 or both ears.

RESULTS:

Short-term area LC stimulation triggered new phantom tones, clicks, and frequency modulated sounds in 5 subjects and altered sound quality of an existing tinnitus percept in 1 subject. The results of this study indicate that perceptual awareness of auditory phantoms is contingent on satisfying a permission condition controlled by the dorsal striatum. Potential auditory phantoms are not automatically gated to reach perceptual awareness. A phantom percept gate control model is proposed.

CONCLUSION:

Neuromodulation of area LC can trigger temporary gate dysfunction and reversibly release new phantoms for conscious awareness. Restoration of restrictive dorsal striatal gate function to treat problematic phantom percepts may be realized by adopting long-term area LC neuromodulation and choosing optimal stimulation parameters.

Tinnitus: Models and mechanisms

Over the past decade, there has been a burgeoning of scientific interest in the neurobiological origins of tinnitus. During this period, numerous behavioral and physiological animal models have been developed which have yielded major clues concerning the likely neural correlates of acute and chronic forms of tinnitus and the processes leading to their induction. The data increasingly converge on the view that tinnitus is a systemic problem stemming from imbalances in the excitatory and inhibitory inputs to auditory neurons. Such changes occur at multiple levels of the auditory system and involve a combination of interacting phenomena that are triggered by loss of normal input from the inner ear. This loss sets in motion a number of plastic readjustments in the central auditory system and sometimes beyond the auditory system that culminate in the induction of aberrant states of activation that include hyperactivity, bursting discharges and increases in neural synchrony. This article will review was has been learned about the biological origins of these alterations, summarize where they occur and examine the cellular and molecular mechanisms that are most likely to underlie them.

Dorsal cochlear nucleus hyperactivity and tinnitus: are they related?

PURPOSE

Eight lines of evidence implicating the dorsal cochlear nucleus (DCN) as a tinnitus contributing site are reviewed. We now expand the presentation of this model, elaborate on its essential details, and provide answers to commonly asked questions regarding its validity.

CONCLUSIONS

Over the past decade, numerous studies have converged to support the hypothesis that the DCN may be an important brain center in the generation and modulation of tinnitus. Although other auditory centers have been similarly implicated, the DCN deserves special emphasis because, as a primary acoustic nucleus, it occupies a potentially pivotal position in the hierarchy of functional processes leading to the emergence of tinnitus percepts. Moreover, because a great deal is known about the underlying cellular categories and the details of synaptic circuitry within the DCN, this brain center offers a potentially powerful model for probing mechanisms underlying tinnitus.

Somatosensory pulsatile tinnitus syndrome: somatic testing identifies a pulsatile tinnitus subtype that implicates the somatosensory system

A new tinnitus syndrome is described: high-pitched, cardiac-synchronous tinnitus, whose pulsations are suppressed by strong contractions or compressions of the neck and jaw muscles (somatic testing). 14 cases, 6 non-lateralized and 8 unilateral, are reported. In the non-lateralized cases, onset was bilateral. In the one intermittent case, while her tinnitus was absent her pulsatile tinnitus could be induced by somatic testing. No etiology was found from physical examination, imaging, or ancillary testing. Because these cases of pulsatile tinnitus can be both induced and suppressed by activation of the somatosensory system of the head or upper lateral neck, we propose that this syndrome is occurring from (a) cardiac synchronous somatosensory activation of the central auditory pathway or (b) failure of the somatosensory-auditory central nervous system interactions to suppress cardiac somatosounds.

Neural mechanisms underlying somatic tinnitus

Somatic tinnitus is clinically observed modulation of the pitch and loudness of tinnitus by somatic stimulation. This phenomenon and the association of tinnitus with somatic neural disorders indicate that neural connections between the somatosensory and auditory systems may play a role in tinnitus. Anatomical and physiological evidence supports these observations. The trigeminal and dorsal root ganglia relay afferent somatosensory information from the periphery to secondary sensory neurons in the brainstem, specifically, the spinal trigeminal nucleus and dorsal column nuclei, respectively. Each of these structures has been shown to send excitatory projections to the cochlear nucleus. Mossy fibers from the spinal trigeminal and dorsal column nuclei terminate in the granule cell domain while en passant boutons from the ganglia terminate in the granule cell domain and core region of the cochlear nucleus. Sources of these somatosensory-auditory projections are associated with proprioceptive and cutaneous, but not nociceptive, sensation. Single unit and evoked potential recordings in the dorsal cochlear nucleus indicate that these pathways are physiologically active. Stimulation of the dorsal column and the cervical dorsal root ganglia elicits short- and long-latency inhibition separated by a transient excitatory peak in DCN single units. Similarly, activation of the trigeminal ganglion elicits excitation in some DCN units and inhibition in others. Bimodal integration in the DCN is demonstrated by comparing responses to somatosensory and auditory stimulation alone with responses to paired somatosensory and auditory stimulation. The modulation of firing rate and synchrony in DCN neurons by somatatosensory input is physiological correlate of somatic tinnitus.

Projections of the second cervical dorsal root ganglion to the cochlear nucleus in rats

Physiological, anatomical, and clinical data have demonstrated interactions between somatosensory and auditory brainstem structures. Spinal nerve projections influence auditory responses, although the nature of the pathway(s) is not known. To address this issue, we injected biotinylated dextran amine into the cochlear nucleus or dorsal root ganglion (DRG) at the second cervical segment (C2). Cochlear nucleus injections retrogradely labeled small ganglion cells in C2 DRG. C2 DRG injections produced anterograde labeling in the external cuneate nucleus, cuneate nucleus, nucleus X, central cervical nucleus, dorsal horn of upper cervical spinal segments, and cochlear nucleus. The terminal field in the cochlear nucleus was concentrated in the subpeduncular corner and lamina of the granule cell domain, where endings of various size and shapes appeared. Examination under an electron microscope revealed that the C2 DRG terminals contained numerous round synaptic vesicles and formed asymmetric synapses, implying depolarizing influences on the target cell. Labeled endings synapsed with the stalk of the primary dendrite of unipolar brush cells, distal dendrites of presumptive granule cells, and endings containing pleomorphic synaptic vesicles. These primary somatosensory projections contribute to circuits that are hypothesized to mediate integrative functions of hearing.

Multisensory integration in the dorsal cochlear nucleus: unit responses to acoustic and trigeminal ganglion stimulation

A necessary requirement for multisensory integration is the convergence of pathways from different senses. The dorsal cochlear nucleus (DCN) receives auditory input directly via the VIIIth nerve and somatosensory input indirectly from the Vth nerve via granule cells. Multisensory integration may occur in DCN cells that receive both trigeminal and auditory nerve input, such as the fusiform cell. We investigated trigeminal system influences on guinea pig DCN cells by stimulating the trigeminal ganglion while recording spontaneous and sound-driven activity from DCN neurons. A bipolar stimulating electrode was placed into the trigeminal ganglion of anesthetized guinea pigs using stereotaxic co-ordinates. Electrical stimuli were applied as bipolar pulses (100 micros per phase) with amplitudes ranging from 10 to 100 microA. Responses from DCN units were obtained using a 16-channel, four-shank electrode. Current pulses were presented alone or preceding 100- or 200-ms broadband noise (BBN) bursts. Thirty percent of DCN units showed either excitatory, inhibitory or excitatory-inhibitory responses to trigeminal ganglion stimulation. When paired with BBN stimulation, trigeminal stimulation suppressed or facilitated the firing rate in response to BBN in 78% of units, reflecting multisensory integration. Pulses preceding the acoustic stimuli by as much as 95 ms were able to alter responses to BBN. Bimodal suppression may play a role in attenuating body-generated sounds, such as vocalization or respiration, whereas bimodal enhancement may serve to direct attention in low signal-to-noise environments.