Comparing Different Montages of Transcranial Direct Current Stimulation in Treating Treatment-Resistant Obsessive–Compulsive Disorder: A Randomized, Single-Blind Clinical Trial

Background: Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation for treatment-resistant obsessive-compulsive disorder (OCD). We aim to compare treatment out-comes with newly developed dual-stie cathodal tDCS over the orbitofrontal cortex (OFC) and pre-supplementary motor area (pre-SMA) and two previously reported montages (cerebel-lum-OFC and pre-SMA) in patients with treatment-resistant OCD. Methods: Eighteen OCD pa-tients were randomly allocated to receive twice-daily 2mA/20min sessions for 10 consecutive weekdays with the active cathode placed on the cerebellum-OFC, bilaterally pre-SMA or OFC-pre-SMA tDCS. The primary outcome was the change of the Yale-Brown Obsessive–Compulsive Scale (Y-BOCS). Resting electroencephalogram (EEG) was recorded to obtain the default mode network (DMN) via low resolution electromagnetic tomography. Each patient re-ceived one-week and one-month follow-ups after 2-week stimulation. Results: At the end of stimulation, the Y-BOCS scores in the cerebellum-OFC, pre-SMA, and OFC-pre-SMA tDCS groups (each group, n=6) was decreased 14.15 ± 13.31, 7.4 ± 9.59, and 20.75 ± 8.70 %, respectively but no significant differences were found between groups. In the OFC-pre-SMA tDCS group, OC symptoms significantly decreased by a mean of -20.75% immediately after the 20th tDCS session and the improvement remained 1 week and 1 month after tDCS. For EEG source functional connectivity (FC) analyses, increased FC within the frontal network was found after OFC-pre-SMA tDCS whereas decreased FC within the DMN was observed after cerebellum-OFC tDCS. Conclusions: Dual-site cathodal tDCS over the OFC and pre-SMA might be the promising montage to treat patients with treatment-resistant OCD. Future studies using randomized sham-controlled designs are needed.