High-definition transcranial direct current stimulation of the dorsolateral prefrontal cortex for tinnitus modulation: a preliminary trial

Tinnitus is the perception of sound in the absence of its external source. Non-invasive neuromodulation techniques have been used in the past decade to investigate the impact of stimulation on tinnitus perception. The objective is to invest the impact of high-definition transcranial direct current stimulation (HD-tDCS) of dorsolateral prefrontal cortex (DLPFC) stimulation on tinnitus loudness and annoyance. Thirteen participants underwent two sessions of HD-tDCS (real and sham) in a double blind, sham controlled, randomized trial. The washout period between the real and sham stimulation session was 1 week. Tinnitus loudness and annoyance was measured using a ten-point tinnitus loudness/annoyance numeric rating scale at the baseline, after 5, 10, 15 and 20 min of stimulation. There was a significant reduction in the tinnitus loudness after the HD-tDCS of DLPFC. A comparison of the different time points (5, 10, 15 and 20 min) with the baseline measurement for tinnitus loudness showed a statistically significant reduction after 15 min (t = 1.82, p = 0.047) and 20 min (t = 1.82, p = 0.047) of stimulation using the real HD-tDCS; this effect was not observed for tinnitus annoyance. HD-tDCS of DLPFC is a safe technique for tinnitus modulation. The most common transient sensations experienced during HD-tDCS were tingling, sleepiness and scalp pain. HD-tDCS of DLPFC resulted in transient tinnitus loudness suppression after 15 min of stimulation. We propose the optimum stimulation duration for HD-tDCS of DLPFC for tinnitus suppression to be 15 min instead of 20 min.