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Transcutaneous electrical nerve stimulation (TENS) is a nonpharmacologic treatment for pain relief. TENS has been used to treat a variety of painful conditions. This review updates the basic and clinical science regarding the use of TENS that has been published in the past 3 years (ie, 2005−2008). Basic science studies using animal models of inflammation show changes in the peripheral nervous system, as well as in the spinal cord and descending inhibitory pathways, in response to TENS. Translational studies show mechanisms to prevent analgesic tolerance to repeated application of TENS. This review also highlights data from recent randomized, placebo-controlled trials and current systematic reviews. Clinical trials suggest that adequate dosing, particularly intensity, is critical to obtaining pain relief with TENS. Thus, evidence continues to emerge from both basic science and clinical trials supporting the use of TENS for the treatment of a variety of painful conditions while identifying strategies to increase TENS effectiveness.

Both HF-TENS and LF-TENS increased PPT in people with knee osteoarthritis; placebo TENS had no significant effect on PPT. Cutaneous pain measures were unaffected by TENS. Subjective pain ratings at rest and during movement were similarly reduced by active TENS and placebo TENS, suggesting a strong placebo component of the effect of TENS.

This study compared a new transient sham TENS that delivers current for 45 seconds to an inactive sham and active TENS to determine the degree of blinding and influence on pain reduction. Pressure pain thresholds (PPT), heat pain thresholds (HPT), and pain intensities to tonic heat and pressure were measured in 69 healthy adults before and after randomization. Allocation investigators and subjects were asked to identify the treatment administered. The transient sham blinded investigators 100% of the time and 40% of subjects compared to the inactive sham that blinded investigators 0% of the time and 21% of subjects. Investigators and subjects were only blinded 7% and 13% of the time, respectively, with active TENS. Neither placebo treatment resulted in significant changes in PPT, HPT, or pain intensities. Subjects using higher active TENS amplitudes (≥17mAs) had significantly higher PPTs and lower pain intensities to tonic pressure than subjects using lower amplitudes (<17mAs). HPTs and pain intensities to tonic heat were not significantly changed. The transient TENS completely blinds investigators to treatment and does not reduce pain, thereby providing a true placebo treatment.

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