Abstract
Pain is managed using a biopsychosocial approach and pharmacological and non-pharmacological treatments. Transcutaneous electrical nerve stimulation (TENS) is a technique whereby pulsed electrical currents are administered through the intact surface of the skin with the intention of alleviating pain, akin to ‘electrically rubbing pain away’. Despite over 50 years of published research, uncertainty about the clinical efficacy of TENS remains. The purpose of this comprehensive review is to critically appraise clinical research on TENS to inform future strategies to resolve the ‘efficacy-impasse’. The principles and practices of TENS are described to provide context for readers unfamiliar with TENS treatment. The findings of systematic reviews evaluating TENS are described from a historical perspective to provide context for a critical evaluation of factors influencing the outcomes of randomized controlled trials (RCTs); including sample populations, outcome measures, TENS techniques, and comparator interventions. Three possibilities are offered to resolve the impasse. Firstly, to conduct large multi-centered RCTs using an enriched enrolment with randomized withdrawal design, that incorporates a ‘run-in phase’ to screen for potential TENS responders and to optimise TENS treatment according to individual need. Secondly, to meta-analyze published RCT data, irrespective of type of pain, to determine whether TENS reduces the intensity of pain during stimulation, and to include a detailed assessment of levels of certainty and precision. Thirdly, to concede that it may be impossible to determine efficacy due to insurmountable methodological, logistical and financial challenges. The consequences to clinicians, policy makers and funders of this third scenario are discussed. I argue that patients will continue to use TENS irrespective of the views of clinicians, policy makers, funders or guideline panel recommendations, because TENS is readily available without prescription; TENS generates a pleasant sensory experience that is similar to easing pain using warming and cooling techniques; and technological developments such as smart wearable TENS devices will improve usability in the future. Thus, research is needed on how best to integrate TENS into existing pain management strategies by analyzing data of TENS usage by expert-patients in real-world settings.
Highlights
Pain is managed using a biopsychosocial approach, and pharmacological and nonpharmacological methods
Therapeutic neuromodulation techniques deliver thermal, mechanical, chemical and electrical stimuli to the body, and are recommended in medicine, physical therapy and nursing for relief of pain
The invention of machines to generate electricity fueled the manufacture of electrotherapeutic devices in the late 1700s, the development of pharmacological based therapies for anesthesia and analgesia meant that electrotherapy was never accepted within mainstream medicine
Summary
Pain is managed using a biopsychosocial approach, and pharmacological and nonpharmacological methods. Interest in electrotherapy to alleviate pain (electroanalgesia) was rekindled in 1965 following the publication of Pain mechanisms: a new theory by Melzack and Wall which suggested that electrical stimulation of low threshold peripheral nerves in the skin could inhibit activity of centrally located nociceptive transmission neurons, relieving pain [2]. Clinical research suggested that TENS reduced pain in patients, but there were relatively few randomized placebo-controlled trials to confirm that benefits were due to electrical currents per se. Three decades have elapsed since the first systematic reviews, yet recent reviews and meta-analyses, including Cochrane reviews, remain inconclusive or conflicting, despite a constant stream of new RCTs. Recommendations from clinical guideline panels about whether to offer TENS are inconsistent, causing uncertainty for patients, practitioners and policy makers. It seems timely to re-examine why such a large amount of published research has failed to resolve the issue of whether TENS alleviates pain
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