Effects of transcutaneous electrical nerve stimulation in complex regional pain syndrome: a systematic review

Complex regional pain syndrome (CRPS) causes disabling pain. Transcutaneous electrical nerve stimulation (TENS) is a treatment option. The aim of this systematic review is to evaluate the effects of TENS in patients with CRPS. A systematic search was conducted in PubMed, EMBASE, Cochrane CENTRAL, Web of Science, and PEDro databases up to June 2025. Randomized controlled trials (RCTs) involving patients with CRPS that evaluated the effects of TENS, regardless of parameters used, on pain intensity were considered eligible. Comparator groups could include placebo, usual care, or no intervention. Two independent reviewers extracted data, and a descriptive synthesis was performed. Risk of bias was assessed using the RoB 2 tool. Of the 517 records screened, only two clinical trials met the inclusion criteria, encompassing a total of 38 participants (58% women). One study reported improvements in pain, mobility, and edema with conventional TENS compared to sham TENS. The other was a feasibility study that did not reach its recruitment target and presented only individual-level data without between-group comparisons. The assessment of the risk of bias revealed some concern about clarity of reporting of data analysis in both studies and the absence of protocol registration in one. There was insufficient evidence to judge the efficacy of TENS for analgesic and function improvement in patients with CRPS. Further studies are needed to inform clinical decision-making. registration number CRD42024554290. Complex regional pain syndrome (CRPS) is a chronic pain condition that can occur after an injury or surgery. It causes severe pain, swelling, skin changes, and difficulty moving the affected body part. TENS (transcutaneous electrical nerve stimulation) is a noninvasive treatment that uses mild electrical impulses to try to relieve pain. This review analyzed scientific studies that investigated the effects of TENS in people with CRPS. The authors searched for studies up to July 2024 in several reputable databases. Of the 490 studies found, only two met the review criteria, with a total of 38 participants. One of these studies showed that TENS can help reduce pain, improve movement, and decrease swelling, when compared to a dummy treatment (placebo). The other study did not have comparisons between groups. In summary, there is not yet enough evidence to say for sure whether TENS is effective in treating CRPS. More well-designed studies with larger numbers of participants are needed to confirm its benefits and better guide healthcare professionals and patients.