Giriraj Singh Shekhawat

Transcranial Direct Current Stimulation Intensity and Duration Effects on Tinnitus Suppression

Background. Perception of sound in the absence of an external auditory source is called tinnitus, which may negatively affect quality of life. Anodal transcranial direct current stimulation (tDCS) of the left temporoparietal area (LTA) was explored for tinnitus relief. Objective. This pilot study examined tDCS dose (current intensity and duration) and response effects for tinnitus suppression. Methods. Twenty-five participants with chronic tinnitus and a mean age of 54 years took part. Anodal tDCS of LTA was carried out. Current intensity (1 mA and 2 mA) and duration (10 minutes, 15 minutes, and 20 minutes) were varied and their impact on tinnitus measured. Results. tDCS was well tolerated. Fifty-six percent of participants (14) experienced transient suppression of tinnitus, and 44% of participants (11) experienced long-term improvement of symptoms (overnight—less annoyance, more relaxed, and better sleep). There was an interaction between duration and intensity of the stimulus on the change in rated loudness of tinnitus, F(2, 48) = 4.355, P = .018, and clinical global improvement score, F(2, 48) = 3.193, P = .050, after stimulation. Conclusions. Current intensity of 2 mA for 20 minutes was the more effective stimulus parameter for anodal tDCS of LTA. tDCS can be a potential clinical tool for reduction of tinnitus, although longer term trials are needed.

Intensity, Duration, and Location of High-Definition Transcranial Direct Current Stimulation for Tinnitus Relief.

Background and Objective. Tinnitus is the perception of a phantom sound. The aim of this study was to compare current intensity (center anode 1 mA and 2 mA), duration (10 minutes and 20 minutes), and location (left temporoparietal area [LTA] and dorsolateral prefrontal cortex [DLPFC]) using 4 × 1 high-definition transcranial direct current stimulation (HD-tDCS) for tinnitus reduction. Methods. Twenty-seven participants with chronic tinnitus (>2 years) and mean age of 53.5 years underwent 2 sessions of HD-tDCS of the LTA and DLPFC in a randomized order with a 1 week gap between site of stimulation. During each session, a combination of 4 different settings were used in increasing dose (1 mA, 10 minutes; 1 mA, 20 minutes; 2 mA, 10 minutes; and 2 mA, 20 minutes). The impact of different settings on tinnitus loudness and annoyance was documented. Results. Twenty-one participants (77.78%) reported a minimum of 1 point reduction on tinnitus loudness or annoyance scales. There were significant changes in loudness and annoyance for duration of stimulation, F(1, 26) = 10.08, P < .005, and current intensity, F(1, 26) = 14.24, P = .001. There was no interaction between the location, intensity, and duration of stimulation. Higher intensity (2 mA) and longer duration (20 minutes) of stimulation were more effective. Conclusions. A current intensity of 2 mA for 20-minute duration was the most effective setting used for tinnitus relief. The stimulation of the LTA and DLPFC were equally effective for suppressing tinnitus loudness and annoyance.

Randomized Trial of Transcranial Direct Current Stimulation and Hearing Aids for Tinnitus Management

Background. The perception of sound in the absence of an external sound is tinnitus. Tinnitus can have a severe negative impact on quality of life. Objective. This trial investigated whether multisession anodal transcranial direct current stimulation (tDCS) of the left temporoparietal area would enhance sound therapy from hearing aids. Methods. Forty participants (mean age = 54 years) experiencing chronic tinnitus (minimum 2 years) completed a 7-month long double-blind randomized clinical trial. Participants were randomized into 2 groups: control receiving sham tDCS and experimental receiving tDCS. Each group underwent multisession (5 consecutive sessions with 24-hour gap) anodal tDCS (2 mA intensity and 20 minutes duration) of the left temporoparietal area, followed by hearing aid use for 6 months. The impact of tDCS and hearing aid use on tinnitus was assessed using questionnaires (primary measure: Tinnitus Functional Index) and minimum masking level measurement. Results. There was a significant reduction in the overall Tinnitus Functional Index score with time, F(2, 37) = 11.9, P = .0001, for both the groups. Similar patterns were seen for secondary measures. tDCS appeared to have a positive effect on minimum masking levels but not questionnaire responses. Conclusions. After 3 months of hearing aid use, there were significant improvements in tinnitus, which were sustained at 6 months of use. The hearing aid effects appeared independent of tDCS. Further investigations of tDCS or other neuromodulators priming the auditory system for sound therapy based tinnitus treatments are warranted.

Modulation of Perception or Emotion? A Scoping Review of Tinnitus Neuromodulation Using Transcranial Direct Current Stimulation

Background. Tinnitus is the phantom perception of sound and can have negative effect on the quality of life. Transcranial direct current stimulation (tDCS) is a noninvasive neuromodulation technique, which can increase or decrease the cortical excitability in the brain region to which it is applied. tDCS has been used for tinnitus research since 2006. Objective. To investigate whether tDCS affects tinnitus perception, related emotion, or both, and the potential implications for tinnitus management. Methods. A scoping review was undertaken using the methods proposed by Arksey and O’Malley. After initial consideration of title relevance and reading abstracts, 15 studies were included in this review. The data from these studies were charted to investigate the impact of tDCS on tinnitus perception and emotions. Results. tDCS results in transient suppression of tinnitus loudness and annoyance; however, it does not lead to long-term impact on tinnitus related emotion. Local stimulation of different sites of stimulation (left temporoparietal area, dorsolateral prefrontal cortex, and auditory cortex) might modulate tinnitus perception (loudness) and emotions differently; however, further research is needed to explore this hypothesis. This review has identified aspects of methodologies that require attention in upcoming tinnitus and tDCS trials to offer better insights. Conclusions. tDCS is an effective research tool for transient tinnitus neuromodulation. However, efforts should be invested in designing clinical trials using local and multiple sites of stimulation, optimized parameters, and objective outcome measures before it can be translated in to a clinical tool for tinnitus management.

Prescription of hearing-aid output for tinnitus relief

Abstract Objective: Tinnitus is a perceived sound that cannot be attributed to an external source. This study attempts to identify a prescription of amplification that is optimized as a first-fit setting for tinnitus relief. Design: Participants compared the effect of high frequency amplification on their tinnitus. Stimuli were 13 speech files with different amounts of high frequency amplification (three cut-off frequencies and four gain settings) to simulate the effects of a change in DSL(I/O) v5.0 prescription in the high frequencies. Study sample: Twenty-five participants with chronic tinnitus participated in the study. Results: A 6-dB reduction to prescribed gain at 2 kHz emerged as the most preferred output (26.47% participants) to interfere with participants’ tinnitus. Overall, 70.58% of the participants’ preferred a 3 to 6 dB reduction in output while 29.42% preferred a similar increase across all cut-off frequencies. A trend was observed in which the higher the tinnitus pitch the more similar the preferred output to DSL(I/O) v5.0. Conclusion: DSL(I/O) v5.0 appears to be a good starting point for prescription of hearing-aid output for tinnitus management. Long-term benefits of different prescriptions for tinnitus still need to be ascertained.

Methodology for studying the transient effects of transcranial direct current stimulation combined with auditory residual inhibition on tinnitus

BACKGROUND Transcranial direct current stimulation (tDCS) and auditory residual inhibition (RI) are short lasting non-invasive techniques that can suppress tinnitus in some people. A pilot study was undertaken to evaluate methods to measure a potential additive effect of these treatments. NEW METHOD Ten participants (mean age 59 years) with chronic tinnitus underwent four sessions of anodal tDCS of the left temporoparietal area(LTA) combined with 1min of auditory stimulation (broadband noise presented at tinnitus minimum masking level [MML]+10 dB), either before, during or immediately after tDCS and in a sham controlled session. Participants continuously monitored and recorded their MML on custom software prior to stimulation, during 20 min of tDCS, and 30 min following tDCS. A tinnitus loudness rating was undertaken before and after completion of testing. RESULTS Nine out of ten participants completed the study, one participant dropped out after two sessions due to self-reported worsening in tinnitus symptoms. Seven out of nine participants reported transient tinnitus suppression when sound stimulation was presented along with tDCS. No reliable change in MML was observed. COMPARISON WITH EXISTING METHOD This is the first study to examine the feasibility of continuously measuring MML while providing a combination of auditory and noninvasive brain stimulation simultaneously. CONCLUSIONS We propose modifications in the protocol used, to find ways to increase the duration of auditory RI and investigate its underlying mechanisms. Recommendations for further research are discussed.

Comparison of the Long-Term Effect of Positioning the Cathode in tDCS in Tinnitus Patients

Objective: Transcranial direct current stimulation (tDCS) is one of the methods described in the literature to decrease the perceived loudness and distress caused by tinnitus. However, the main effect is not clear and the number of responders to the treatment is variable. The objective of the present study was to investigate the effect of the placement of the cathode on the outcome measurements. Methods: Patients considered for the trial were chronic non-pulsatile tinnitus patients with complaints for more than 3 months and a Tinnitus Functional Index (TFI) score that exceeded 25. The anode was placed on the right dorsolateral prefrontal cortex (DLPFC). In the first group—“bifrontal”—the cathode was placed on the left DLPFC, while in the second group—“shoulder”—the cathode was placed on the shoulder. Each patient received two sessions of tDCS weekly and eight sessions in total. Evaluations took place on the first visit for an ENT consultation, at the start of therapy, after eight sessions of tDCS and at the follow-up visit, which took place 84 days after the start of the therapy. Subjective outcome measures such as TFI, Visual Analog Scales (VAS) for loudness and percentage of consciousness of tinnitus were administered in every patient. Results: There was no difference in the results for tinnitus loudness and the distress experienced between the placement of the cathode on the left DLPFC or on the shoulder. In addition, no statistically significant overall effect was found between the four test points. However, up to 39.1% of the patients experienced a decrease in loudness, measured by the VAS for loudness. Moreover, 72% of those in the bifrontal group, but only 46.2% of those in the shoulder group reported some improvement in distress. Conclusion: While some improvement was noted, this was not statistically significant. Both electrode placements stimulated the right side of the hippocampus, which could be responsible for the effect found in both groups. Further research should rule out the placebo effect and investigate alternative electrode positions.

A crossover trial comparing wide dynamic range compression and frequency compression in hearing aids for tinnitus therapy

Abstract Purpose: It has been suggested that frequency lowering may be a superior tinnitus reducing digital signal processing (DSP) strategy in hearing aids than conventional amplification. A crossover trial was undertaken to determine if frequency compression (FC) was superior to wide dynamic range compression (WDRC) in reducing tinnitus. Method: A 6–8-week crossover trial of two digital signal-processing techniques (WDRC and 2 WDRC with FC) was undertaken in 16 persons with high-frequency sensorineural hearing loss and chronic tinnitus. Results: WDRC resulted in larger improvements in Tinnitus Functional Index and rating scale scores than WDRC with FC. The tinnitus improvements obtained with both processing types appear to be due to reduced hearing handicap and possibly decreased tinnitus audibility. Conclusions: Hearing aids are useful assistive devices in the rehabilitation of tinnitus. FC was very successful in a few individuals but was not superior to WDRC across the sample. It is recommended that WDRC remain as the default first choice tinnitus hearing aid processing strategy for tinnitus. FC should be considered as one of the many other options for selection based on individual hearing needs. Implications of Rehabilitation Hearing aids can significantly reduce the effects of tinnitus after 6–8 weeks of use. Addition of frequency compression digital signal processing does not appear superior to standard amplitude compression alone. Improvements in tinnitus were correlated with reductions in hearing handicap.

Optimization of Transcranial Direct Current Stimulation of Dorsolateral Prefrontal Cortex for Tinnitus: A Non-Linear Dose-Response Effect

Neuromodulation is defined as the process of augmenting neuroplasticity via invasive or non-invasive methods. Tinnitus is the perception of sound in the absence of its external source. The objective of this study was to optimize the parameters of transcranial direct current stimulation (tDCS) of dorsolateral prefrontal cortex (DLPFC) for tinnitus suppression. The following factors were optimized in the dose-response design (n = 111): current intensity (1.5 mA or 2 mA), stimulation duration (20 min or 30 min), and number of stimulation sessions (2, 4, 6, 8, or 10), with a 3–4 day washout period between each session. Participants underwent a minimum of 2 sessions in 1 week or maximum of 10 sessions in 5 weeks’ time. Tinnitus loudness was measured in pre-post design using a 10-point numeric rating scale. There was a significant reduction in tinnitus loudness after tDCS of DLPFC. There was no significant difference between the intensity and duration of stimulation. As the number of sessions increased, there was a higher reduction in the tinnitus loudness; however, this effect plateaued after 6 sessions.

Effects of Electrical Stimulation in Tinnitus Patients: Conventional Versus High-Definition tDCS

Background. Contradictory results have been reported for transcranial direct current stimulation (tDCS) as treatment for tinnitus. The recently developed high-definition tDCS (HD tDCS) uses smaller electrodes to limit the excitation to the desired brain areas. Objective. The current study consisted of a retrospective part and a prospective part, aiming to compare 2 tDCS electrode placements and to explore effects of HD tDCS by matched pairs analyses. Methods. Two groups of 39 patients received tDCS of the dorsolateral prefrontal cortex (DLPFC) or tDCS of the right supraorbital–left temporal area (RSO-LTA). Therapeutic effects were assessed with the tinnitus functional index (TFI), a visual analogue scale (VAS) for tinnitus loudness, and the hyperacusis questionnaire (HQ) filled out at 3 visits: pretherapy, posttherapy, and follow-up. With a new group of patients and in a similar way, the effects of HD tDCS of the right DLPFC were assessed, with the tinnitus questionnaire (TQ) and the hospital anxiety and depression scale (HADS) added. Results. TFI total scores improved significantly after both tDCS and HD tDCS (DLPFC: P < .01; RSO-LTA: P < .01; HD tDCS: P = .05). In 32% of the patients, we observed a clinically significant improvement in TFI. The 2 tDCS groups and the HD tDCS group showed no differences on the evolution of outcomes over time (TFI: P = .16; HQ: P = .85; VAS: P = .20). Conclusions. TDCS and HD tDCS resulted in a clinically significant improvement in TFI in 32% of the patients, with the 3 stimulation positions having similar results. Future research should focus on long-term effects of electrical stimulation.