Trans-electrical nerve stimulation (TENS) for somatic tinnitus

Blast Overpressures as a Military and Occupational Health Concern

PURPOSE

This tutorial reviews effects of environmental stressors like blast overpressures and other well-known acoustic contaminants (continuous, intermittent, and impulsive noise) on hearing, tinnitus, vestibular, and balance-related functions. Based on the overall outcome of these effects, detailed consideration is given to the health and well-being of individuals.

METHOD

Because hearing loss and tinnitus are consequential in affecting quality of life, novel neuromodulation paradigms are reviewed for their positive abatement and treatment-related effects. Examples of clinical data, research strategies, and methodological approaches focus on repetitive transcranial magnetic stimulation (rTMS) and electrical stimulation of the vagus nerve paired with tones (VNSt) for their unique contributions to this area.

RESULTS

Acoustic toxicants transmitted through the atmosphere are noteworthy for their propensity to induce hearing loss and tinnitus. Mounting evidence also indicates that high-level rapid onset changes in atmospheric sound pressure can significantly impact vestibular and balance function. Indeed, the risk of falling secondary to loss of, or damage to, sensory receptor cells in otolith organs (utricle and saccule) is a primary reason for this concern. As part of the complexities involved in VNSt treatment strategies, vocal dysfunction may also manifest. In addition, evaluation of temporospatial gait parameters is worthy of consideration based on their ability to detect and monitor incipient neurological disease, cognitive decline, and mortality.

CONCLUSION

Highlighting these respective areas underscores the need to enhance information exchange among scientists, clinicians, and caregivers on the benefits and complications of these outcomes.

[Somatosensory tinnitus]

BACKGROUND

Somatosensory tinnitus represents a clinically significant subgroup of chronic tinnitus. Although not completely understood, increasing evidence suggests interactivity between the somatosensory and auditory systems is responsible for both the development and maintenance of tinnitus.

OBJECTIVES

The aim of this study is to provide an overview of the evaluation of somatosensory tinnitus and to propose an examination protocol to support the diagnosis and treatment of this patient group.

MATERIALS AND METHODS

In addition to patient history, various clinical examination maneuvers are presented to establish the diagnosis of somatosensory tinnitus.

RESULTS

The maneuvers can be divided into examinations of the cervical spine, temporomandibular joint, and soft tissue near the jaw. The maneuvers should be performed in a quiet environment and usually in comparison between sides.

CONCLUSION

Accurate and efficient diagnosis of somatosensory tinnitus is essential to initiate appropriate treatment. The clinical maneuvers presented here are well suited for this purpose.

Effectiveness of bimodal auditory and electrical stimulation in patients with tinnitus: A feasibility study

Background

Tinnitus is a common symptom, affecting about 10–15% of the adult population. When input from the somatosensory system can influence and/or elicit tinnitus, this type of subjective tinnitus is called somatosensory tinnitus. Recently, a new type of bimodal neurostimulation treatment has shown promising results for a specific subgroup within the somatosensory tinnitus population. It is, however, not clear if this bimodal stimulation is also effective in patients with other types of subjective tinnitus.

Aim

The aim of this study was to evaluate the feasibility and efficacy of non-invasive bimodal auditory-somatosensory stimulation in reducing tinnitus severity among a general population of people with subjective tinnitus.

Methods

Chronic subjective tinnitus patients were recruited from the ENT department of the Antwerp University Hospital. Somatosensory stimulation was delivered by Transcutaneous Electrical Nerve Stimulation (TENS), and it was combined with auditory stimulation via headphones. The therapy comprised six sessions of thirty minutes twice a week for a period of 3 consecutive weeks. Follow up measurements were scheduled 9–12 weeks after the last treatment session. The change of the Tinnitus Functional Index (TFI) score, a questionnaire evaluating tinnitus burden and effects on the quality of life, was the primary outcome measure.

Results

Twenty-nine patients were enrolled in the study. A linear mixed-effects model was used to analyze the efficacy of bimodal treatment. The results of this analysis showed a statistically significant decrease (by 6, 9 points) in average TFI score at the follow up visit when compared to baseline. The ability to modulate tinnitus did not have an influence on the treatment results.

Conclusion

Our study showed that bimodal stimulation is a feasible and safe method of tinnitus treatment. The method might be an effective treatment for some participants with tinnitus, especially those who have accompanying neck/temporomandibular problems, although, the evidence from this trial is quite weak. Additional research is needed toward establishing the optimal treatment protocol, as well as selecting the most appropriate inclusion criteria.

Effect of adding a supervised physical therapy exercise program to photobiomodulation therapy in the treatment of cervicogenic somatosensory tinnitus: A randomized controlled study

OBJECTIVES

To evaluate the effectiveness of adding a supervised physical therapy exercise program to photobiomodulation therapy (PBMT) in the treatment of cervicogenic somatosensory tinnitus (CST).

METHODS

Forty patients suffering from CST with age 45-55 years were included in the study. They were assigned randomly into 2 groups, 20 per each. (Study group) Group (A) received a supervised physical therapy exercise program in addition to 20 minutes PBMT with a 650-nanometer wavelength and a 5 milliWatt power output, spot size of 1 cm2, and energy density of 6 Joules, 3 sessions per week for 8 consecutive weeks, plus traditional medical treatment. While (control group), group (B) received the same PBMT protocol, 3 sessions per week for 8 consecutive weeks in addition to the traditional medical treatment. Tinnitus visual analog scaling (VAS), tinnitus handicap inventory (THI), and cervical range of motion (ROM) were measured at baseline and after 8 weeks.

RESULTS

Mixed MANOVA showed a statistically significant reduction in tinnitus VAS, THI, and a significant improvement in cervical ROM (flexion, extension, right bending, left bending, right rotation, and left rotation) in favor of Group A (P < .05). There was a significant decrease in posttreatment VAS treatment (P > .001) MD [-2.05(-2.68:-1.41)], and THI relative to pretreatment mean difference [-5.35(-8.51: -2.19)] and a significant increase in posttreatment neck ROM in Groups A and B relative to pretreatment neck ROM (P > .001). Flexion range posttreatment MD[3.65(1.64:5.65)], Extension MD [6.55(1.35:11.75)], right bending MD[3.8(2.51:5.08)], left bending MD[1.75(0.19:3.3)], right rotation MD [3.5(1.28:5.71)] and left rotation [2.75(0.67:4.82)].

CONCLUSIONS

Adding a supervised physical therapy exercise program to PBMT showed positive and beneficial effects in the treatment of CST using VAS, THI, and Cervical ROM assessment tools.

Transcutaneous Electric Nerve Stimulation in Chronic Subjective Tinnitus

OBJECTIVE

It is aimed to determine the therapeutic role of transcutaneous electrical nerve stimulation (TENS) on chronic subjective tinnitus with a randomized and comparative analysis.

METHOD

46 individuals with normal hearing, chronic subjective tinnitus, aged 20-65; randomly divided into the study (TENS therapy) and tje control groups. The control group (n = 23) was informed only about tinnitus, while the study group (n = 23) received TENS therapy (20 sessions in 4 weeks). Before TENS therapy, tinnitus-related evaluations of all participants [tinnitus frequency, loudness, minimum masking level (MMS), residual inhibition (RI)] were made and Tinnitus Handicap Inventory (THI), Visual Analogue Scale (VAS), Short Form 36 (SF-36), and The Quality of Life Scale were applied to the participants. These evaluations and questionnaires were repeated after 4 weeks of the therapy.

RESULTS

There was a significant decrease in the tinnitus severity after TENS therapy in the study group (p = 0.003). Moreover, it was found that VAS (loudness and annoyance), THI (functional, emotional and total score), SF-36 (physical function, physical role, pain, general health, vitality, emotional role and social function) values improved compared to before TENS therapy and the difference was significant (p < 0.05). There was no significant difference between the first and last evaluations of the control group (p > 0.05).

CONCLUSION

TENS is an effective, practical and reliable therapy method in reducing severity, loudness, and annoyance of tinnitus, and increasing the quality of life in individuals with chronic subjective tinnitus.

Effectiveness of Kinesio taping in the treatment of somatosensory tinnitus: A randomized controlled trial

BACKGROUND AND PURPOSE

The clinical effects of Kinesio taping (KT) for somatosensory tinnitus have not been confirmed. The purpose of this study is to investigate the efficacy of KT applied to the sternocleidomastoid, upper trapezius, and levator scapulae muscles for somatosensory tinnitus associated with neck complaints.

MATERIALS AND METHODS

Thirty-patients were randomly assigned to the KT group (n = 15) and the sham-taping (ST) group (n = 15). Tinnitus-severity was measured using a visual analog scale (tinnitus-VAS) as a primary outcome. Tinnitus Handicap Inventory (THI), cervical pain-VAS, and neck disability index (NDI) were used for the assessments of tinnitus handicap, neck pain, and disability.

RESULTS

Tinnitus-VAS, THI, cervical pain-VAS, and NDI improved significantly in the KT group after the intervention (all P ≤ 0.001). In the ST group, no significant differences in outcome measures were found in the fourth-week.

CONCLUSION

KT is more effective than sham-taping in improving somatosensory tinnitus associated with neck complaints.

Vagus nerve stimulation paired with tones for tinnitus suppression: Effects on voice and hearing

OBJECTIVE

In individuals with chronic tinnitus, our interest was to determine whether daily low-level electrical stimulation of the vagus nerve paired with tones (paired-VNSt) for tinnitus suppression had any adverse effects on motor-speech production and physiological acoustics of sustained vowels. Similarly, we were also interested in evaluating for changes in pure-tone thresholds, word-recognition performance, and minimum-masking levels. Both voice and hearing functions were measured repeatedly over a period of 1 year.

STUDY DESIGN

Longitudinal with repeated-measures.

METHODS

Digitized samples of sustained frontal, midline, and back vowels (/e/, /o/, /ah/) were analyzed with computer software to quantify the degree of jitter, shimmer, and harmonic-to-noise ratio contained in these waveforms. Pure-tone thresholds, monosyllabic word-recognition performance, and MMLs were also evaluated for VNS alterations. Linear-regression analysis was the benchmark statistic used to document change over time in voice and hearing status from a baseline condition.

RESULTS

Most of the regression functions for the vocal samples and audiometric variables had slope values that were not significantly different from zero. Four of the nine vocal functions showed a significant improvement over time, whereas three of the pure tone regression functions at 2-4 kHz showed some degree of decline; all changes observed were for the left ear, all were at adjacent frequencies, and all were ipsilateral to the side of VNS. However, mean pure-tone threshold changes did not exceed 4.29 dB from baseline and therefore, would not be considered clinically significant. In some individuals, larger threshold shifts were observed. No significant regression/slope effects were observed for word-recognition or MMLs.

CONCLUSION

Quantitative voice analysis and assessment of audiometric variables showed minimal if any evidence of adverse effects using paired-VNSt over a treatment period of 1 year. Therefore, we conclude that paired-VNSt is a safe tool for tinnitus abatement in humans without significant side effects.

LEVEL OF EVIDENCE

Level IV.

The effect of transcutaneous electrical nerve stimulation (TENS) on chronic subjective tinnitus

OBJECTIVES

Chronic Subjective Tinnitus is a very highly prevalent disorder worldwide. There is no definitive treatment. The aim of this study is to investigate the efficacy of transcutaneous electrical nerve stimulation (TENS) applied to the auricula for treating tinnitus using the Depression Anxiety Stress Scales (DASS) and Tinnitus Handicap Inventory (THI).

METHODS

The 60 patients were randomly divided into 3 groups of 20 patients. The first group (A) had one ear stimulated with TENS, and the second group (B) had both ears stimulated. Group C (placebo group) received no electrical or sound stimulation. All group patients received total of 10 sessions with a maximum of 4 days between the sessions.

RESULTS

The THI and DASS scores decreased significantly after the treatment (p < 0.05). A significant difference was also observed between the groups after treatment (p < 0.05). While there was no difference between group A and B, it was shown that group C's post-treatment score was significantly higher than those of both groups (p < 0.05.) CONCLUSION: It is important to note that TENS has a therapeutic effect on subjective chronic tinnitus as well as a placebo effect.

A simulation environment for studying transcutaneous electrotactile stimulation

Transcutaneous electrical nerve stimulation (TENS) allows the artificial excitation of nerve fibres by applying electric-current pulses through electrodes on the skin's surface. This work involves the development of a simulation environment that can be used for studying transcutaneous electrotactile stimulation and its dependence on electrode layout and excitation patterns. Using an eight-electrode array implementation, it is shown how nerves located at different depths and with different orientations respond to specific injected currents, allowing the replication of already reported experimental findings and the creation of new hypotheses about the tactile sensations associated with certain stimulation patterns. The simulation consists of a finite element model of a human finger used to calculate the distribution of the electric potential in the finger tissues neglecting capacitive effects, and a cable model to calculate the excitation/inhibition of action potentials in each nerve.

A Pilot Randomized Controlled Trial of Transcutaneous Electrical Nerve Stimulation for Patients With Acute Tinnitus

BACKGROUND

This pilot study aimed to evaluate the feasibility effectiveness and safety of transcutaneous electrical nerve stimulation (TENS) for patients with acute tinnitus.

METHODS

A total of 46 eligible patients with acute tinnitus were entered and included in this randomized controlled trial. All the included patients were equally and randomly divided into a verum TENS group and a sham TENS group, each group 23 participants. All patients received parenteral intramuscular therapy of 1 ml Vitamin B12 weekly for a total of 4 weeks. In addition, they also underwent verum or sham TENS 30 min daily, 3 times weekly for 4 weeks. The primary efficacy endpoint was measured by the Tinnitus Severity Scale (TSS) and Tinnitus Questionnaire (TQ) sum score. The secondary efficacy endpoints were assessed by the Tinnitus Handicap Inventory (THI), 12-Item Short Form Health Survey (SF-12) questionnaire, and adverse events. All outcome efficacy endpoints were measured at baseline and after 4 weeks of treatment.

RESULTS

After 4-week treatment, the patients undergoing verum TENS showed statistically efficacy of symptoms relief, as measured by the scales of TSS (P < .01), TQ (P < .01), and THI (P < .01), and improvement of quality of life, as assessed by the SF-12 (P < .01), compared with patients receiving sham TENS. In addition, no adverse events related to the treatment were recorded in either group.

CONCLUSIONS

The results of this study showed that verum TENS may benefit patients with acute tinnitus after 4 weeks of 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.

Tinnitus: Is there a place for brain stimulation?

Tinnitus is the perception of a “phantom sound” and has a high prevalence. Although many therapies have been investigated within the last decades, there is still no effective standard therapy. Animal studies and human functional imaging studies revealed that tinnitus perception is associated with many complex changes in multiple brain structures. There is growing evidence that brain stimulation might be able to interrupt the local altered neuronal activity and hereby inhibit tinnitus perception. In this editorial review, an update is given on the most promising targets for brain stimulation. Promising structures for stimulation are the dorsal cochlear nucleus, the inferior colliculus and the medial geniculate body of the thalamus. For cortical stimulation, the auditory cortex is considered as a target. Nevertheless, the field is waiting for evidence from well-designed clinical trials, based on supporting evidence from experimental/mechanistic research, to support or discourage the application of brain stimulation in tinnitus.

Cervical epidural steroid injection for refractory somatic tinnitus

Somatic tinnitus is a common disorder, yet few treatments described in the literature have demonstrated strong efficacy. We report a case of a 61-year-old male with refractory somatic tinnitus, temporally related to a prior bacterial otitis media, wherein auditory symptoms were successfully treated with cervical epidural injections of long-acting corticosteroid. We discuss the proposed mechanism of somatic tinnitus and the means by which neuraxial steroids may inhibit somatic tinnitus symptoms.

Prevalence and factors associated with neck and jaw muscle modulation of tinnitus

Forceful contractions of neck and jaw muscles have consistently been shown to modulate tinnitus and can be used to screen patients who are responsive to somatic stimulation and, therefore, optimal candidates for somatosensory-based treatment. To identify the factors associated with somatic modulation of tinnitus, 163 patients underwent 19 neck and jaw maneuvers after an extensive physiological and audiological profile was compiled. Overall, tinnitus was modulated in 57.1% of ears tested. Unilateral tinnitus showed greater prevalence of modulation. Neck maneuvers generally decreased tinnitus loudness, whereas jaw maneuvers increased loudness. Female gender and buzzing tinnitus were associated with a high prevalence of modulation and a decrease in tinnitus loudness. Loud tinnitus and low-pitched tonal tinnitus were associated with exacerbation of the condition as a result of somatic testing. Use of these characteristics to select optimal candidates for somatosensory-based tinnitus therapies may be essential for the development of an effective approach for tinnitus treatment.

Acoustic overexposure increases the expression of VGLUT-2 mediated projections from the lateral vestibular nucleus to the dorsal cochlear nucleus

The dorsal cochlear nucleus (DCN) is a first relay of the central auditory system as well as a site for integration of multimodal information. Vesicular glutamate transporters VGLUT-1 and VGLUT-2 selectively package glutamate into synaptic vesicles and are found to have different patterns of organization in the DCN. Whereas auditory nerve fibers predominantly co-label with VGLUT-1, somatosensory inputs predominantly co-label with VGLUT-2. Here, we used retrograde and anterograde transport of fluorescent conjugated dextran amine (DA) to demonstrate that the lateral vestibular nucleus (LVN) exhibits ipsilateral projections to both fusiform and deep layers of the rat DCN. Stimulating the LVN induced glutamatergic synaptic currents in fusiform cells and granule cell interneurones. We combined the dextran amine neuronal tracing method with immunohistochemistry and showed that labeled projections from the LVN are co-labeled with VGLUT-2 by contrast to VGLUT-1. Wistar rats were exposed to a loud single tone (15 kHz, 110 dB SPL) for 6 hours. Five days after acoustic overexposure, the level of expression of VGLUT-1 in the DCN was decreased whereas the level of expression of VGLUT-2 in the DCN was increased including terminals originating from the LVN. VGLUT-2 mediated projections from the LVN to the DCN are likely to play a role in the head position in response to sound. Amplification of VGLUT-2 expression after acoustic overexposure could be a compensatory mechanism from vestibular inputs in response to hearing loss and to a decrease of VGLUT-1 expression from auditory nerve fibers.

Cuneate and spinal trigeminal nucleus projections to the cochlear nucleus are differentially associated with vesicular glutamate transporter-2

There are distinct distributions and associations with vesicular glutamate transporters (VGLUTs) for auditory nerve and specific somatosensory projections in the cochlear nucleus (CN). Auditory nerve fibers project primarily to the magnocellular areas of the ventral cochlear nucleus and deepest layer of the dorsal cochlear nucleus and predominantly colabel with VGLUT1; whereas the spinal trigeminal nucleus (Sp5) projections terminate primarily in the granule cell domains (GCD) of CN and predominantly colabel with VGLUT2. Here, we demonstrate that the terminals of another somatosensory pathway, originating in the cuneate nucleus (Cu), also colabel with VGLUT2. Cu projections in cochlear nucleus exhibited a bilateral distribution pattern with ipsilateral dominance, with 30% of these classified as putative mossy fibers (MFs) and 70% as small boutons (SBs). Cu anterograde endings had a more prominent distribution in the GCD than Sp5, with a higher percentage of MF terminals throughout the CN and higher MF/SB ratio in GCD. 56% of Cu endings and only 25% of Sp5 endings colabeled with VGLUT2. In both cases these were mostly MFs with only 43% of Cu SBs and 18% of Sp5 SBs colabeled with VGLUT2. The few Cu and Sp5 terminals that colabeled with VGLUT1 (11% vs. 1%), were evenly distributed between MFs and SBs. The high number of VGLUT2-positive Cu MFs predominantly located in the GCD, may reflect a faster-acting pathway that activates primarily dorsal cochlear nucleus cells via granule cell axons. In contrast, the higher percentage of Sp5-labeled SB terminals and a greater number of projections outside the GCD suggest a slower-acting pathway that activates both dorsal and ventral cochlear nucleus principal cells. Both projections, with their associations to VGLUT2 likely play a role in the enhancement of VGLUT2 after unilateral deafness [Zeng C, Nannapaneni N, Zhou J, Hughes LF, Shore S (2009) J Neurosci 29:4210-4217] that may be associated with tinnitus.

Qigong for the treatment of tinnitus: a prospective randomized controlled study

OBJECTIVE

Tinnitus is a frequent disorder which is very difficult to treat. Qigong is a mindful exercise and an important constituent of traditional Chinese medical practice. Here we performed a randomized controlled trial to evaluate the effect of a Qigong intervention on patients with tinnitus. We hypothesized that especially tinnitus patients with somatosensoric components may benefit from the mind-body technique of Qigong.

METHODS

Eighty patients with tinnitus of at least 3 months duration were randomly assigned to an intervention group (n=40) consisting of 10 Qigong training sessions in 5 weeks or a waiting-list control group (n=40). Tinnitus severity was assessed with a visual analogue scale (VAS) and with a tinnitus questionnaire (TBF-12) before treatment, immediately after treatment, and 1 and 3 months after treatment.

RESULTS

Qigong did not cause any side effects and was completed by 80% of the assigned patients. Compared with the control group, Qigong participants experienced improvement in tinnitus severity, as reflected by a significant reduction in both the VAS and the TBF-12. In the subgroup of patients with somatosensoric tinnitus, Qigong effects were more pronounced, resulting in a highly significant improvement in both scales compared to the waiting-list group.

CONCLUSION

These findings suggest that Qigong interventions could be a useful complement to the therapeutic management of patients with tinnitus and especially for those with somatosensoric components. Satisfaction with the intervention, a high degree of completion, and stability of the effects for at least 3 months after the intervention further underscore the potential of Qigong in the treatment of tinnitus.

Transcutaneous electrical nerve stimulation (TENS) of upper cervical nerve (C2) for the treatment of somatic tinnitus

Somatic tinnitus has been defined as tinnitus temporally associated to a somatic disorder involving the head and neck. Several studies have demonstrated the interactions between the somatosensory and auditory system at the dorsal cochlear nucleus (DCN), inferior colliculus, and parietal association areas. The objective is to verify the effect of transcutaneous electrical nerve stimulation of the upper cervical nerve (C2) in the treatment of somatic tinnitus. As electrical stimulation of C2 increases activation of the DCN through the somatosensory pathway and enlarges the inhibitory role of the DCN on the central nervous system, C2 TENS can be considered for tinnitus modulation. A total of 240 patients in whom tinnitus is modulated by somatosensory events (e.g., tinnitus change with rotation, retro- and antiflexion of neck) or modulated by pressure on head or face were included in this study. Both a real and a sham TENS treatment were applied for 30 min (10 min of 6 Hz, followed by 10 min of 40 Hz and 10 min of sham). Significant tinnitus suppression was found (P < 0.001). Only 17.9% (N = 43) of the patients with tinnitus responded to C2 TENS. They had an improvement of 42.92%, and six patients had a reduction of 100%.

Tinnitus: characteristics, causes, mechanisms, and treatments

Tinnitus-the perception of sound in the absence of an actual external sound-represents a symptom of an underlying condition rather than a single disease. Several theories have been proposed to explain the mechanisms underlying tinnitus. Tinnitus generators are theoretically located in the auditory pathway, and such generators and various mechanisms occurring in the peripheral auditory system have been explained in terms of spontaneous otoacoustic emissions, edge theory, and discordant theory. Those present in the central auditory system have been explained in terms of the dorsal cochlear nucleus, the auditory plasticity theory, the crosstalk theory, the somatosensory system, and the limbic and autonomic nervous systems. Treatments for tinnitus include pharmacotherapy, cognitive and behavioral therapy, sound therapy, music therapy, tinnitus retraining therapy, massage and stretching, and electrical suppression. This paper reviews the characteristics, causes, mechanisms, and treatments of tinnitus.

Controversy: Does repetitive transcranial magnetic stimulation/ transcranial direct current stimulation show efficacy in treating tinnitus patients?

BACKGROUND

Tinnitus affects 10% of the population, its pathophysiology remains incompletely understood, and treatment is elusive. Functional imaging has demonstrated a relationship between the intensity of tinnitus and the degree of reorganization in the auditory cortex. Experimental studies have further shown that tinnitus is associated with synchronized hyperactivity in the auditory cortex. Therefore, targeted modulation of auditory cortex has been proposed as a new therapeutic approach for chronic tinnitus.

METHODS

Repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) are noninvasive methods that can modulate cortical activity. These techniques have been applied in different ways in patients with chronic tinnitus. Single sessions of high-frequency rTMS over the temporal cortex have been successful in reducing the intensity of tinnitus during the time of stimulation and could be predictive for treatment outcome of chronic epidural stimulation using implanted electrodes.

RESULTS

Another approach that uses rTMS as a treatment for tinnitus is application of low-frequency rTMS in repeated sessions, to induce a lasting change of neuronal activity in the auditory cortex beyond the duration of stimulation. Beneficial effects of this treatment have been consistently demonstrated in several small controlled studies. However, results are characterized by high interindividual variability and only a moderate decrease of the tinnitus. The role of patient-related (for example, hearing loss, tinnitus duration, age) and stimulation-related (for example, stimulation site, stimulation protocols) factors still remains to be elucidated.

CONCLUSIONS

Even in this early stage of investigation, there is a convincing body of evidence that rTMS represents a promising tool for pathophysiological assessment and therapeutic management of tinnitus. Further development of this technique will depend on a more detailed understanding of the neurobiological effects mediating the benefit of TMS on tinnitus perception. Moreover clinical studies with larger sample sizes and longer follow-up periods are needed.