Randomized Controlled Trial of Transcranial Direct Current Stimulation over the Supplementary Motor Area in Tourette Syndrome.

BACKGROUND

Transcranial direct current stimulation (tDCS) over the supplementary motor area (SMA) has shown promise in Tourette syndrome (TS), but previous studies were limited in size and stimulation duration.

OBJECTIVE

The aim was to explore the efficacy and safety of multiple sessions of cathodal tDCS over the bilateral SMA on tic severity in TS.

METHODS

A double-blind, randomized, sham-controlled trial 1 mA cathodal tDCS over bilateral SMA was performed in participants with TS older than 16 years. The intervention involved two 20-min periods of stimulation with either sham or active tDCS per day, over 5 consecutive days, during which participants actively suppressed tics. Tic severity was measured using the Yale Global Tic Severity Scale Total Tic Severity (YGTSS-TTS, primary outcome) score at baseline, day 5 (visit 5), and 1 week later (visit 6). Questionnaires focusing on comorbidities were performed at baseline and visit 6.

RESULTS

Twenty-four participants were randomly assigned (12 active, 12 sham; 8 women; median age: 26). We observed a significant effect of visit on YGTSS-TSS, but no significant effect of treatment or treatment × visit interaction emerged. In contrast, a statistically significant effect of the treatment × visit interaction was observed for the motor tic subscore, with significantly larger improvement in the active arm. Furthermore, we detected a significantly larger decrease in premonitory urge intensity at visit 6 after active stimulation. No effect was detected on severity of comorbidities.

CONCLUSIONS

This preliminary study suggests that bilateral tDCS over the SMA provides small, but significant benefits in reducing motor tic severity in TS.