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.