The Evaluation of Effects of Electrical Stimulation in Treatment of Patients with Chronic Tinnitus with Normal Hearing Sensitivity.

Tinnitus is usually associated with different comorbidities such as anxiety, annoyance and depression. Evidences have targeted two main places for tinnitus treatment, namely the auditory cortex and the dorsolateral prefrontal cortex (DLPFC). Transcranial direct current stimulation (tDCS) has been reportedly associated with improvement of cognitive functions in individuals. This study was conducted to evaluate the therapeutic effects of repeated sessions of anodal bifrontal tDCS on tinnitus symptoms. Furthermore, the tDCS impacts on the comorbid depression and anxiety of the patients were investigated. Forty-two voluntaries that suffers from chronic tinnitus were randomly assigned into "real tDCS" (n = 21) and "sham tDCS" (n = 21) groups. The tDCS group, received tDCS with the protocol consisted of 2 mA current, daily one session of 20 min, 6 consecutive days per week and for 4 consecutive weeks. The tinnitus handicap inventory (THI) scale, was measured before the first tDCS session and at one-week and two weeks follow-up. With the same intervals; the distress-related tinnitus was evaluated using visual analogue scale. Depression and anxiety scores were also measured using the Beck depression inventory and Beck anxiety inventory scales, respectively. Our findings indicated that THI score, depression and anxiety level has been gradually diminished across subsequent measurement intervals. We also find significant reduction of distress-related tinnitus in the real-tDCS group after treatment. We conclude that application of tDCS to the bilateral DLPFC region alleviates chronic tinnitus and it should be considered in patients with refractory tinnitus.