Repeated sessions of transcranial direct current stimulation for treatment of chronic subjective tinnitus: a pilot randomized controlled trial

Subjective tinnitus is an auditory phantom sensation characterized by the perception of sound in the absence of an identifiable external source. This distressing audiological symptom can severely affect the quality of life. Transcranial direct current stimulation (tDCS) is a noninvasive technique that can induce short-term relief in tinnitus in some patients. The purpose of this pilot double-blind randomized controlled trial was to investigate whether repeated application of anodal tDCS over left temporoparietal area could induce long-lasting relief in patients with chronic tinnitus. Twenty-two patients with chronic tinnitus for at least 6 months were randomly allocated into two groups and received five sessions of anodal (N = 11) or sham (N = 11) stimulation in five consecutive days. A current intensity of 2 mA for 20 min was used for anodal stimulation. Outcomes were assessed using Persian version of tinnitus handicap inventory (THI), loudness and distress visual analog scale (VAS) scores and clinical global impression (CGI) scale. The trial is registered at the Iranian Registry of Clinical Trials (IRCT) with the reference ID of IRCT2014082018871N1. No statistically significant difference was found between anodal and sham stimulation regarding either immediate or long-lasting effects over the 2 weeks follow-up period. Deterioration of symptoms and alteration in tinnitus characteristics were reported by a few patients. There were no significant long-term beneficial effects following tDCS of the left temporoparietal area.