Optimization of High Definition Transcranial Direct Current Stimulation (HDtDCS) For Tinnitus Relief

Objective: Tinnitus is the phantom perception of sound. The aim of this study was to optimize 4 × 1 high definition transcranial direct current stimulation (HD-tDCS) current intensity (centre anode 1 mA and 2 mA), duration (10 minutes and 20 minutes) and location (Left Temporoparietal Area [LTA] and Dorsolateral Prefrontal Cortex [DLPFC]) for tinnitus relief. Methods: Twenty seven participants with chronic tinnitus (>2 years) and mean age of 53.5 years underwent two sessions of HD-tDCS of LTA and DLPFC in a randomized order with a 1 week gap. During each session a combination of 4 different stimulation settings were used in incremental order (1 mA, 10 min; 1 mA, 20 min; 2 mA, 10 min; and 2 mA, 20 min) and their impact on tinnitus loudness and annoyance was documented. Results: In total 21 participants reported a minimum of 1 point reduction on tinnitus loudness or annoyance scales. There was a significant main effect for time F (1, 26) = 10.08, p < 0.005 and current intensity F (1, 26) = 16.84, p < 0.001, for loudness change and annoyance change [time F (1, 26) = 6.88, p = 0.01 and current intensity F (1, 26) = 14.24, p = 0.001]. There was no interaction between the location, intensity, and duration of stimulation. Conclusions: A current intensity of 2 mA for 20 minute duration was the most effective setting used for tinnitus relief. The stimulation of the LTA and DLPFC were equally effective for suppressing tinnitus loudness and annoyance.