Effects of Transcranial Direct Current Stimulation on pain and pain-related outcomes: an umbrella review.

Background: This study examines Transcranial Direct Current Stimulation (tDCS), a non-invasive brain stimulation technique, as an alternative for pain management given the limitations of pharmacological treatments.

Methods: We searched PubMed, Scopus, and the Cochrane Library for systematic reviews and meta-analyses (SRMAs) on the efficacy of tDCS across pain-related conditions. Outcomes included treatment regimens, mechanisms, effects, and adverse events. Methodological quality was assessed with AMSTAR-2 and evidence levels with GRADE.

Results: Forty-one SRMAs were included. Positive effects were observed across 14 pain-related conditions, including 10 pain mechanism-specific outcomes and 6 other pain-related outcomes. Analgesic effects were reported in the short-, mid-, and long-term (up to 4 weeks), especially with stimulation over the primary motor cortex.

Conclusions: Our findings suggest that tDCS might be effective for fibromyalgia, migraine, and neuropathic pain associated with spinal cord injury and stroke. However, further evidence is needed for chronic orofacial pain, multiple sclerosis, knee osteoarthritis, central post-stroke pain, intra-abdominal pain, and phantom limb pain. As most of the evidence stems from reviews with "critically low" quality, more high-quality studies are needed in the future.