A new evidence-based review from the American Academy of Neurology concludes that transcutaneous electric nerve stimulation (TENS) is not recommended for use in treating chronic low-back pain but adds that TENS should be considered to treat diabetic neuropathy.
The report, from the academy's Therapeutics and Technology Assessment Subcommittee, was published online December 30 in Neurology. Authors on the new document are Richard M. Dubinsky, MD, MPH, from Kansas University Medical Center in Kansas City, and Janis Miyasaki, MD, MEd, from Toronto Western Hospital, Ontario, Canada.
"In the highest-quality studies of chronic low back pain, there was no benefit of TENS compared to sham or placebo TENS, leaving us to conclude that it is of no benefit, and make a recommendation that it should not be used for chronic low back pain," Dr. Dubinsky told Medscape Neurology.
In diabetic polyneuropathy, some studies showed slight benefit, he added. "We concluded it should be considered in the treatment of diabetic polyneuropathy."
TENS has been used to treat neurologic and other disorders for decades, the authors write. The biologic basis of its analgesic effect is not known, but it is used is based on the gate theory of pain, they note. In this assessment, the authors carried out a systematic literature search of Medline and Cochrane Library up to April 2009, looking for controlled clinical trials in which TENS was used to treat pain associated with neurological conditions.
Acute low back pain not normally seen in neurologic conditions was not considered in this review. All but 1 of the studies excluded patients with known causes of low-back pain, such as pinched nerves, severe scoliosis, severe spondylolisthesis, or obesity.
"We only found 2 conditions that had adequate rigor in the research, and that was chronic back pain and diabetic polyneuropathy," Dr. Dubinsky said.
The studies included showed conflicting results in chronic low back pain. Two class 2 studies showed benefit, but 2 class 1 studies and another class 2 study showed no benefit. "Because the Class I studies are stronger evidence, TENS is established as ineffective for the treatment of chronic low back pain," they write.
Two class 2 studies suggested that TENS is probably effective in treating painful diabetic neuropathy. The only specific neurologic cause of chronic low-back pain in which TENS was studied was multiple sclerosis, for which TENS was not shown to be of benefit.
The document makes 2 main recommendations:
- TENS is not recommended for the treatment of chronic low-back pain because of a lack of proven efficacy (level A, 2 class 1 studies).
- TENS should be considered for the treatment of painful diabetic neuropathy (level B, 2 class 2 studies).
The document also gives some guidance on the need for further research into TENS, Dr. Dubinsky noted. Among their recommendations were determining what the best paradigm is, in terms of current, pulse-width, and frequency, and then using it in patients who are naive to TENS so that they will be truly blinded to treatment allocation, and studying TENS in patients with well-defined neurological conditions.
Absence of Evidence
In an editorial accompanying the new document, Andreas Binder, MD, and Ralf Baron, MD, from the Division of Neurological Pain Research and Therapy in the Department of Neurology at Christian-Albrechts-Universität Kiel, Germany, write that the conclusions of Dr. Dubinsky and Dr. Miyasaki "may heat up the discussion on the usability of TENS and may be viewed as supporting the critics who questioned the value of TENS in pain therapy.
"However," they add, "absence of evidence is not evidence of absence. The clinical impact of meta-analyses is always limited by the quantity and quality of conducted trials."
TENS has had a long-standing role in pain management, is easy to handle, has a favorable benefit-to-risk ratio, and can be discontinued easily if it is not efficacious — all "desirable properties when treating pain," they write. The new document calls for further trials and even provides "clearcut recommendations for their conduction," they note.
"This updated evidence-based review is valuable in providing the limits of our evidence base," Dr. Binder and Dr. Baron conclude. "Nevertheless, it is not unreasonable to take a practical position that, in spite of the relatively weak scientific and clinical evidence, TENS still represents a valuable therapeutic alternative in neurologic pain disorders.
"Taking the favorable benefit-risk ratio when compared with other pain relieving methods into account, TENS remains a valuable part in the armamentarium of pain therapy."