Effects of add-on transcranial direct current stimulation on pain in Korean patients with fibromyalgia

Despite promising preliminary results of transcranial direct current stimulation (tDCS) treatment in patients with fibromyalgia (FM), several issues need to be addressed, including its limited efficacy, low response rate, and poor tolerability. We investigated the efficacy and safety of tDCS as an add-on treatment for chronic pain in Korean patients with FM. This study enrolled 46 patients who were refractory to pain medications from May 2016 to February 2017. A conventional tDCS device was used to supply 2 mA of current for 20 min on five consecutive days. The primary end-point was a change in visual analogue scale (VAS) pain score at the end of treatment; secondary end-points included changes in Fibromyalgia Impact Questionnaire (FIQ), Brief Pain Inventory (BPI), Brief Fatigue Inventory (BFI), Beck Depression Inventory (BDI), State-Trait Anxiety Inventory (STAI), and Medical Outcomes Study Sleep Scale (MOS-SS) scores. After tDCS, 46 patients showed clinical improvements in VAS pain scores on days 6, 13, and 36 compared with day 0 (p < 0.001). Improvement in FIQ was seen on day 13. The BDI decreased significantly on days 6 and 36, and BFI improved significantly on days 6 and 13. There were no significant improvements in STAI-I, STAI-II, and MOS-SS scores after tDCS. No serious adverse events were observed. Our results suggest that tDCS can result in significant pain relief in FM patients and may be an effective add-on treatment.