Abstract
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.
Highlights
Tinnitus is the perception of sound in the absence of a corresponding external sound source (Eggermont and Roberts, 2004) and is a very common problem
Focusing on the measurements before and after the eight sessions of transcranial Direct Current Stimulation (tDCS), we found that 26.8% (n = 7) of the bifrontal group and 37.5% (n = 9) of the shoulder group experienced an improvement of 1 or more on the Visual Analog Scales (VAS) for maximum loudness, while 30.6% (n = 8) of the subjects in the bifrontal group and 39.1% (n = 9) of the subjects in the shoulder group showed an improvement on the VAS for mean loudness
Most studies have reported a positive effect of tDCS on tinnitus loudness and distress immediately after a tDCS session (Vanneste et al, 2010; Vanneste and De Ridder, 2011; Joos et al, 2014); in this study, we focused on the long-term effect
Summary
Tinnitus is the perception of sound in the absence of a corresponding external sound source (Eggermont and Roberts, 2004) and is a very common problem. 25.3% of the US population reports having tinnitus, while 7.9% experience tinnitus frequently (Shargorodsky et al, 2010). Tinnitus affects daily activities and can lead to a high level of distress. The literature describes several mechanisms and structures that could be involved in tinnitus. The findings reported cannot always be repeated and the proposed brain structures do not always match. It is certain that it is the auditory system which is responsible for inducing tinnitus (Jastreboff, 1990). Multiple non-auditory systems involved in cognition, emotion and memory play an important role (De Ridder et al, 2014)
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