Dual-site rTMS is More Effective than Single-site rTMS in Tinnitus Patients: A Blinded Randomized Controlled Trial

Sequential Multilocus Repetitive Transcranial Magnetic Stimulation for Treatment of Tinnitus With and Without Comorbid Major Depressive Disorder

OBJECTIVE

Repetitive transcranial magnetic stimulation (rTMS) is a promising treatment for tinnitus, although outcomes are highly variable. We previously described a multilocus sequential rTMS treatment protocol for tinnitus involving stimulation of both prefrontal and auditory targets. In this study, we report results using this approach in an open-label treatment study of tinnitus with and without comorbid major depressive disorder (MDD).

MATERIALS AND METHODS

Forty patients with chronic tinnitus (mean age 56 years, ten female) and with (n = 17) or without (n = 23) MDD received multilocus rTMS administered sequentially to 1) left dorsolateral prefrontal cortex, followed by 2) auditory cortex (Heschel's gyrus). Patients completed weekly self-report ratings using the Tinnitus Functional Index (TFI) and Tinnitus Handicap Inventory, and patients with MDD completed the Inventory of Depressive Symptomatology Self-Report 30-item.

RESULTS

Patients showed significant mean improvement in tinnitus at sessions 5 (mean TFI improvement 6.8 points ± 12.2, p = 0.002) and 10 (mean improvement 9.2 points ± 14.1, p = 0.002), with 48% of patients responding within ten treatment sessions. Responders were significantly older than nonresponders (61.5 ± 15 years vs 51.3 ± 16 years), and there was a trend toward decreased likelihood of response in subjects with comorbid MDD compared with subjects without comorbidity (odds ratio = 0.28, p = 0.06). Patients with comorbid MDD reported significantly less improvement after ten sessions than did those with tinnitus alone (4.3 ± 10.3 vs 14.7 ± 15.0 points, p = 0.04). Post hoc analyses suggested that the comorbid group achieved improvement comparable to that of the tinnitus-only group after 30 treatments.

CONCLUSIONS

Patients showed significant improvement in tinnitus from multilocus sequential rTMS treatment, and those with tinnitus alone improved more quickly. Those with depression who continued rTMS through a full 30-session course further improved, indicating that tinnitus with comorbid MDD may respond with extended treatment.

Neuromodulation for Treatment of Tinnitus: A Systematic Review and Meta-Analysis

OBJECTIVE

To evaluate the treatment efficacy of neuromodulation versus sham for the treatment of tinnitus.

DATA SOURCES

Cochrane Library, CINAHL, PubMed, Scopus.

REVIEW METHODS

The Cochrane Library, CINAHL, PubMed, and Scopus were searched from inception through May 2023 for English language articles documenting "neuromodulation" and "tinnitus" stratified by sham-controlled randomized control trials with 40 or more patients. Data collected included Beck Anxiety Inventory, Beck Depression Inventory (BDI), Tinnitus Handicap Inventory (THI), Tinnitus Questionnaire, and Visual Analog Scale. A Meta-analysis of continuous measures (mean) and proportions (%) were conducted.

RESULTS

A total of 19 randomized control trials (N = 1186) were included. The mean age was 48.4 ± 5.3 (range: 19-74), mean duration of tinnitus was 3.8 ± 3.4 years, 61% [56.2-65.7] male, and 55.7% [46-65] with unilateral tinnitus. The short-term effect of transcutaneous electrical nerve stimulation and transcranial direct current stimulation on THI score is -16.2 [-23.1 to -9.3] and -19 [-30.1 to -7.8], respectively. The long-term effect of repetitive transcranial magnetic stimulation on THI score is -8.6 [-11.5 to -5.7]. Transcranial direct current stimulation decreases BDI score by -11.8 [-13.3 to -10.3].

CONCLUSION

As measured by the Tinnitus Handicap Index, our findings suggest the effects of transcutaneous electrical nerve stimulation and transcranial direct current stimulation reach significant benefit in the short term, whereas repetitive transcranial magnetic stimulation reaches significant benefit in the long term. Based on the BDI, transcranial direct current stimulation significantly reduces comorbid depression in patients with tinnitus.

Focal tDCS of auditory cortex in chronic tinnitus: A randomized controlled mechanistic trial

OBJECTIVE

The goal of this pilot study was to understand how focal transcranial direct current stimulation (tDCS) targeting auditory cortex changes brain function in chronic tinnitus using magnetic resonance imaging (MRI).

METHODS

People with chronic tinnitus were randomized to active or sham tDCS on five consecutive days in this mechanistic trial (n = 10/group). Focal 4x1 tDCS (central anode, surround cathodes) targeted left auditory cortex, with single-blind 2 mA current during twenty-minute sessions. Arterial spin-labeled and blood oxygenation level dependent MRI occurred immediately before and after the first tDCS session, and tinnitus symptoms were measured starting one week before the first tDCS session and through four weeks after the final session.

RESULTS

Acute increases in cerebral blood flow and functional connectivity were noted in auditory cortex after the first active tDCS session. Reduced tinnitus loudness ratings after the final tDCS session correlated with acute change in functional connectivity between an auditory network and mediodorsal thalamus and prefrontal cortex. Reduced tinnitus intrusiveness also correlated with acute change in connectivity between precuneus and an auditory network.

CONCLUSIONS

Focal auditory-cortex tDCS can influence function in thalamus, auditory, and prefrontal cortex, which may associate with improved tinnitus.

SIGNIFICANCE

With future refinement, tDCS targeting auditory cortex could become a viable intervention for tinnitus.

Focal transcranial direct current stimulation of auditory cortex in chronic tinnitus: A randomized controlled mechanistic trial

Objective

The goal of this pilot MRI study was to understand how focal transcranial direct current stimulation (tDCS) targeting auditory cortex changes brain function in chronic tinnitus.

Methods

People with chronic tinnitus were randomized to active or sham tDCS on five consecutive days in this pilot mechanistic trial (n=10/group). Focal 4×1 tDCS (central anode, surround cathodes) targeted left auditory cortex, with single-blind 2mA current during twenty-minute sessions. Arterial spin-labeled and blood oxygenation level dependent MRI occurred immediately before and after the first tDCS session, and tinnitus symptoms were measured starting one week before the first tDCS session and through four weeks after the final session.

Results

Acute increases in cerebral blood flow and functional connectivity were noted in auditory cortex after the first active tDCS session. Reduced tinnitus loudness ratings after the final tDCS session correlated with acute change in functional connectivity between an auditory network and mediodorsal thalamus and prefrontal cortex. Reduced tinnitus intrusiveness also correlated with acute change in connectivity between precuneus and an auditory network.

Conclusions

Focal auditory-cortex tDCS can influence function in thalamus, auditory, and prefrontal cortex, which may associate with improved tinnitus.

Significance

With future refinement, noninvasive brain stimulation targeting auditory cortex could become a viable intervention for tinnitus.

Unresolved Issues Associated with Transcranial Magnetic Stimulation (TMS) Treatment of Chronic Tinnitus

Transcranial magnetic stimulation (TMS) has been investigated as a potential treatment for chronic tinnitus for 20 years. Numerous studies have reported that repetitive TMS (rTMS) has demonstrated efficacy for reducing the severity of tinnitus and its associated co-conditions such as depression, anxiety, and insomnia. However, some researchers have reported that active rTMS is no more effective than sham (placebo) rTMS as a tinnitus treatment method. There are numerous unresolved issues in this field that need to be addressed before rTMS can become a viable treatment for tinnitus. These issues include the type or brand of TMS system and its configuration; coil type, orientation, and placement method; scalp or neural target; laterality of rTMS application; dual site vs. single site stimulation; stimulation frequency and intensity; number of sessions; number of pulses per session; determination of the resting motor threshold (rMT); characteristics of the study population and their tinnitus; and outcome measures and follow-up assessments. To address and resolve these issues, large-scale, multi-site clinical trials of rTMS for tinnitus need to be conducted to determine which rTMS protocols are the most effective. In the absence of such investigations, the issues that need to be studied and addressed remain unresolved and continue to impede the clinical application of this treatment method.

Brain Connectivity Signature Extractions from TMS Invoked EEGs

(1) Background: The correlations between brain connectivity abnormality and psychiatric disorders have been continuously investigated and progressively recognized. Brain connectivity signatures are becoming exceedingly useful for identifying patients, monitoring mental health disorders, and treatment. By using electroencephalography (EEG)-based cortical source localization along with energy landscape analysis techniques, we can statistically analyze transcranial magnetic stimulation (TMS)-invoked EEG signals, for obtaining connectivity among different brain regions at a high spatiotemporal resolution. (2) Methods: In this study, we analyze EEG-based source localized alpha wave activity in response to TMS administered to three locations, namely, the left motor cortex (49 subjects), left prefrontal cortex (27 subjects), and the posterior cerebellum, or vermis (27 subjects) by using energy landscape analysis techniques to uncover connectivity signatures. We then perform two sample t-tests and use the (5 × 10^-5) Bonferroni corrected p-valued cases for reporting six reliably stable signatures. (3) Results: Vermis stimulation invoked the highest number of connectivity signatures and the left motor cortex stimulation invoked a sensorimotor network state. In total, six out of 29 reliable, stable connectivity signatures are found and discussed. (4) Conclusions: We extend previous findings to localized cortical connectivity signatures for medical applications that serve as a baseline for future dense electrode studies.

Brain alterations in patients with intractable tinnitus before and after rTMS: A resting-state functional magnetic resonance imaging study

OBJECTIVE

To observe abnormal tinnitus activity by evaluating the amplitude of low-frequency fluctuation (ALFF) changes in the brain was which detected by resting-state functional magnetic resonance imaging (rs-fMRI) in patients with intractable tinnitus before and after repetitive transcranial magnetic stimulation (rTMS). We hypothesized that rTMS could progressively revert local brain function back to a relatively normal range.

METHODS

This prospective observational research study recruited 25 patients with intractable tinnitus, with 28 healthy controls matched by age, sex, and education level. Participants' Tinnitus Handicap Inventory (THI) scores and the visual analog scale (VAS) were used to determine the severity of their tinnitus before and after treatment. We processed the brain spontaneous neural activity of intractable tinnitus patients by ALFF, then, we determined its association with clinically evaluated indicators of intractable tinnitus.

RESULTS

The total and the three sub-modules (functional [F], emotional [E], and catastrophic [C]) score of the THI and VAS in patients with intractable tinnitus decreased after treatment (P < 0.001). The effective rate of tinnitus patients was 66.9%. A few patients had a slight left facial muscle tremor or temporary mild scalp pain during treatment. Compared with healthy controls, participants with tinnitus significantly reduced ALFF within the left and right medial superior frontal gyrus (P < 0.005). After rTMS treatment, the left fusiform gyrus and right superior cerebellar lobe increased ALFF in those with tinnitus (P < 0.005). The changes in THI, VAS, and ALFF were positively correlated (P < 0.05).

CONCLUSION

RTMS is effective in the treatment of tinnitus. It significantly reduces the THI/VAS score and improves the symptoms of tinnitus. No serious adverse reaction during rTMS were reported. The changes in the left fusiform gyrus and right superior part of the cerebellum may explain the mechanism of rTMS treatment in intractable tinnitus.

State of the art: non-invasive electrical stimulation for the treatment of chronic tinnitus

Subjective tinnitus is the perception of sound in the absence of external stimulation. Neuromodulation is a novel method with promising properties for application in tinnitus management. This study sought to review the types of non-invasive electrical stimulation in tinnitus to provide the foothold for further research. PubMed, EMBASE, and Cochrane databases were searched for studies on the modulation of tinnitus by non-invasive electrical stimulation. Among the four forms of non-invasive electrical modulation, transcranial direct current stimulation, transcranial random noise stimulation, and transauricular vagus nerve stimulation yielded promising results, whereas the effect of transcranial alternating current stimulation in the treatment of tinnitus has not been confirmed. Non-invasive electrical stimulation can effectively suppress tinnitus perception in some patients. However, the heterogeneity in parameter settings leads to scattered and poorly replicated findings. Further high-quality studies are needed to identify optimal parameters to develop more acceptable protocols for tinnitus modulation.

Sequential Prefrontal and Temporoparietal Repetitive Transcranial Magnetic Stimulation (rTMS) for Treatment of Tinnitus With and Without Comorbid Depression: A Case Series and Systematic Review

Background

Tinnitus distress is related to both the loudness and intrusiveness of the tinnitus percept. Treatment approaches targeting both attentional/limbic and auditory systems may better alleviate tinnitus distress than approaches targeting the auditory system alone.

Materials and Methods

Ten subjects with chronic tinnitus received sequential rTMS treatment involving: 1) excitatory stimulation administered to the left dorsolateral prefrontal cortex (DLPFC) or inhibitory stimulation administered to the right DLPFC, followed by 2) inhibitory stimulation administered to primary auditory cortex (Heschel's gyrus or HG). A systematic literature review was performed to evaluate the existing literature on sequential repetitive Transcranial Magnetic Stimulation (rTMS) treatment approaches for tinnitus. Results of the case series are interpreted in the context of tinnitus neurobiology and the extant literature.

Results

Subjects experienced a significant decrease (average 21.7%) in symptoms on the Tinnitus Functional Index (TFI). Those with tinnitus alone experienced a greater mean symptom reduction than those with comorbid MDD (27.7 vs. 17.0%, respectively). Adverse effects were transient and minor. Literature review confirmed that sequential approaches had some advantages compared to single site rTMS; in general, the addition of 1 Hz treatment at DLPFC was superior to single site rTMS in the short term (1-12 weeks), while the addition of 20 Hz treatment at DLPFC appeared superior in the long term (90-180 days).

Conclusions

Sequential rTMS approaches for the treatment of tinnitus-particularly those administering low-frequency treatment at left DLPFC-merit further investigation.

Personalization of Repetitive Transcranial Magnetic Stimulation for the Treatment of Chronic Subjective Tinnitus

Background: Personalization of repetitive transcranial magnetic stimulation (rTMS) for tinnitus might be capable to overcome the heterogeneity of treatment responses. The assessment of loudness changes after short rTMS protocols in test sessions has been proposed as a strategy to identify the best protocol for the daily treatment application. However, the therapeutic advantages of this approach are currently not clear. The present study was designed to further investigate the feasibility and clinical efficacy of personalized rTMS as compared to a standardized rTMS protocol used for tinnitus. Methods: RTMS personalization was conducted via test sessions and reliable, sham-superior responses respectively short-term reductions in tinnitus loudness following active rTMS protocols (1, 10, 20 Hz, each 200 pulses) applied over the left and right temporal cortex. Twenty pulses at a frequency of 0.1 Hz served as a control condition (sham). In case of a response, patients were randomly allocated to ten treatment sessions of either personalized rTMS (2000 pulses with the site and frequency producing the most pronounced loudness reduction during test sessions) or standard rTMS (1 Hz, 2000 pulses left temporal cortex). Those participants who did not show a response during the test sessions received the standard protocol as well. Results: The study was terminated prematurely after 22 patients (instead of 50 planned) as the number of test session responders was much lower than expected (27% instead of 50%). Statistical evaluation of changes in metric tinnitus variables and treatment responses indicated only numerical, but not statistical superiority for personalized rTMS compared to standard treatment. Conclusions: The current stage of investigation does not allow for a clear conclusion about the therapeutic advantages of personalized rTMS for tinnitus based on test session responses. The feasibility of this approach is primarily limited by the low test session response rate.

The Pathological Mechanisms and Treatments of Tinnitus

Tinnitus is defined as the ringing, hissing, clicking or roaring sounds an individual consciously perceives in the absence of an external auditory stimulus. Currently, the literature on the mechanism of tinnitus pathology is multifaceted, ranging from tinnitus generation at the cellular level to its perception at the system level. Cellular level mechanisms include increased neuronal synchrony, neurotransmission changes and maladaptive plasticity. At the system level, the role of auditory structures, non-auditory structures, changes in the functional connectivities in higher regions and tinnitus networks have been investigated. The exploration of all these mechanisms creates a holistic view on understanding the changes the pathophysiology of tinnitus undertakes. Although tinnitus percept may start at the level of cochlear nerve deafferentation, the neuronal changes in the central auditory system to the neuronal and connectivity changes in non-auditory regions, such as the limbic system, become cardinal in chronic tinnitus generation. At the present moment, some tinnitus generation mechanisms are well established (e.g., increased neuronal synchrony) whereas other mechanisms have gained more traction recently (e.g., tinnitus networks, tinnitus-distress networks) and therefore, require additional investigation to solidify their role in tinnitus pathology. The treatments and therapeutics designed for tinnitus are numerous, with varied levels of success. They are generally two-fold: some treatments focus on tinnitus cessation (including cochlear implants, deep brain stimulation, transcranial direct current stimulation and transcranial magnetic stimulation) whereas the other set focuses on tinnitus reduction or masking (including hearing aids, sound therapy, cognitive behavioral therapy, tinnitus retraining therapy, and tailor made notched musical training).  Tinnitus management has focused on implementing tinnitus masking/reducing therapies more than tinnitus cessation, since cessation treatments are still lacking in streamlined treatment protocols and long-term sustainability and efficacy of the treatment. This review will focus on concisely exploring the current and most relevant tinnitus pathophysiology mechanisms, treatments and therapeutics.

Prediction of response to repetitive transcranial magnetic stimulation in phantom sounds based on individual brain anatomy

Non-invasive brain stimulation can reduce the severity of tinnitus phantom sounds beyond the time of stimulation by inducing regional neuroplastic changes. However, there are no good clinical predictors for treatment outcome. We used machine learning to investigate whether brain anatomy can predict therapeutic outcome. Sixty-one chronic tinnitus patients received repetitive transcranial magnetic stimulation of left dorsolateral prefrontal and temporal cortex. Before repetitive transcranial magnetic stimulation, a structural magnetic resonance image was obtained from all patients. To predict individual treatment response in new subjects, we employed a support vector machine ensemble for individual out-of-sample prediction. In the cross-validation, the support vector machine ensemble based on stratified sub-sampling and feature selection yielded an area under the curve of 0.87 for prediction of therapy success in new, previously unseen subjects. This corresponded to a balanced accuracy of 83.5%, sensitivity of 77.2% and specificity of 87.2%. Investigating the most selected features showed the involvement of the auditory cortex but also revealed a network of non-auditory brain areas. These findings suggest that idiosyncratic brain patterns accurately predict individual responses to repetitive transcranial magnetic stimulation treatment for tinnitus. Our findings may hence pave the way for future investigations into the precision treatment of tinnitus, involving automatic identification of the appropriate treatment method for the individual patient.