The Effects of Transcranial Direct Current Stimulation in Patients with Chronic Intractable Peripheral Neuropathic Pain: A Randomized Sham-Controlled Study

Objectives: Transcranial direct current stimulation (tDCS) has demonstrated efficacy in managing neuropathic pain associated with spinal cord injury and fibromyalgia, with a low incidence of adverse effects. This study aimed to evaluate the effects of tDCS in patients with refractory peripheral neuropathic pain. Material and Methods: In this prospective, randomized, double-blind, sham-controlled study, 12 patients with chronic intractable peripheral neuropathic pain (≥6 months) were randomly allocated to receive either active tDCS (2 mA for 20 minutes) or sham stimulation for 5 consecutive days. The primary outcome was pain reduction, measured using the Numeric Rating Scale (NRS) at baseline, daily during stimulation (days 1-5), and post-treatment (weeks 1, 2, 4, and 6). Secondary outcomes included the Neuropathic Pain Symptom Inventory (NPSI) and the EQ-5D-5L at the 4-week follow-up. Adverse events were recorded. Results: Active tDCS resulted in a statistically significant pain reduction on days 2, 3, and 5 compared to the sham group (NRS reduction: Day 2, 5.00±2.37 vs. 1.67±1.75, p-value=0.020; day 3, 5.17±2.32 vs. 1.83±1.94, p-value=0.022; day 5, 5.50±2.07 vs. 2.67±2.25, p-value=0.047). However, no significant differences in pain reduction were observed at weeks 1, 2, 4, or 6. NPSI and EQ-5D-5L scores also showed no significant differences between the groups at the 4-week follow-up. Adverse events were mild and comparable between the groups. Conclusion: tDCS demonstrated significant short-term pain relief in patients with chronic intractable peripheral neuropathic pain. However, larger studies with longer follow-up periods are required to validate its long-term efficacy.