Background: Transcutaneous electrical nerve stimulation (TENS) has been used for decades to manage pain. Although the mechanism is not fully known, TENS theoretically addresses the gate theory of pain by applying a mild electrical current to cutaneous nerve fibers. Surface electrodes and electrical stimulation usually at, or just under, the sensory threshold are used for a set duration. The electrical current, pulse width, and frequency of the current are adjusted depending on the condition. There is conflicting evidence in the literature about the effectiveness of this treatment for neurologic disorders, such as chronic low back pain and painful diabetic neuropathy. Dubinsky and Miyasaki reviewed the evidence for TENS in these disorders.
The Study: The authors searched Medline and the Cochrane Library from study inception to April 2009 for relevant studies involving more than 10 participants and comparing TENS with placebo (TENS-sham, a nonfunctioning identical unit) or with another therapy for well-defined painful neurologic disorders. One trial studied the effectiveness of blinding with TENS versus sham, and found it to be effective. The levels of evidence were also reviewed for each study. Prospective, randomized controlled trials were put into Class I. Class II included prospective matched group cohort studies. Class III included all other controlled trials with well-defined natural history controls or with patients serving as their own controls. Class IV evidence came from uncontrolled studies, case series, case reports, or expert opinion.
Results: Of 263 identified studies, five met inclusion criteria for low back pain and three for diabetic neuropathy. For low back pain, two Class I studies compared TENS with TENS-sham, and one study also compared exercise with no exercise; these studies were powered to detect a 20 percent reduction in pain as measured on a visual analog scale. Both studies (245 patients) showed no benefit with TENS (although exercise was beneficial compared with no exercise). Among the three Class II trials (84 patients), two showed a modest benefit in a variety of TENS modalities, whereas the third showed no benefit.
Of the three studies evaluating TENS for painful diabetic neuropathy, two Class II studies and one Class III study (70 patients) compared TENS with TENS-sham and found a modest reduction in pain with treatment.
Conclusion: The authors conclude that TENS is ineffective for the treatment of chronic low back pain, but is probably effective for reducing pain caused by diabetic peripheral neuropathy.