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The Transcutaneous Electrical Nerve Stimulation treatment of pain is achieved by the use of a Transcutaneous Electrical Nerve Stimulator, more commonly referred to as a TENS unit and pronounced tens, is an electronic device that produces electrical signals used to stimulate nerves through unbroken skin. The name was coined by Dr. Charles Burton.[1] The unit is usually connected to the skin using two or more electrodes. A typical battery-operated TENS unit consists of a pulse generator, small transformer, frequency and intensity controls, and a number of electrodes.


Electrical stimulation for pain control was used in ancient Rome, 63 A.D. It was reported by Scribonius Largus that pain was relieved by standing on an electrical fish at the seashore.[2] In the 16th through the 18th century various electrostatic devices were used for headache and other pains. Benjamin Franklin was a proponent of this method for pain relief. In the nineteenth century a device called the electreat, along with numerous other devices were used for pain control and cancer cures. Only the electreat survived into the twentieth century, but was not portable, and had limited control of the stimulus.{{Citation needed|date=March 2012}


The first modern, patient-wearable TENS was patented in the United States in 1974.[3] It was initially used for testing the tolerance of chronic pain patients to electrical stimulation before implantation of electrodes in the spinal cord dorsal column.[4] The electrodes were attached to an implanted receiver, which received its power from an antenna worn on the surface of the skin. Although intended only for testing tolerance to electrical stimulation, manyTemplate:Weasel-inline of the patients said they received so much relief from the TENS itself that they never returned for the implant. [citation needed]

A number of companies began manufacturing TENS units after the commercial success of the Medtronic device became known.[citation needed] The neurological division of Medtronic, founded by Don Maurer, Ed Schuck and Dr. Charles Ray, developed a number of applications for implanted electrical stimulation devices for treatment of epilepsy, Parkinson's disease, and other disorders of the nervous system.

Today many people confuse TENS with Electro Muscle Stimulation (EMS). EMS and TENS devices look similar, with both using long electric lead wires and electrodes. TENS is for blocking pain, where EMS is for stimulating muscles.


Medical uses


TENS is a non-invasive, low risk nerve stimulation intended to reduce pain, both acute and chronic. Controversy exists as to its effectiveness in the treatment of chronic pain. One review from 2007 felt that the evidence supports a benefit in chronic musculoskeletal pain[5] while another review from the Cochrane Collaboration in 2008 deemed the evidence of poor quality and thus no conclusions were possible regarding chronic pain.[6] Results from a task force on neck pain, in 2008, found no clinically significant benefit to TENS for the treatment of neck pain when compared to placebo treatment.[7] A 2010 review did not find evidence to support the use of TENS for chronic low back pain.[8][9] There is tentative evidence that it may be useful for painful diabetic neuropathy.[8] and knee osteoarthritis;[17][18][19]

An adequate intensity of stimulation is necessary to achieve pain relief with TENS.[10][11]. An analysis of treatment fidelity (meaning that the delivery of TENS in a trial was in accordance with current clinical advice, such as using "a strong but comfortable sensation" and suitable, frequent treatment durations) showed that higher fidelity trials tended to have a positive outcome.[12] In palliative care and pain medicine, TENS units are sometimes used in an attempt to alleviate neuropathic pain (pain due to nerve damage). Although results are modest, some patients benefit from this approach. A suitable cream should be used to increase conductivity from the electrode to the skin. The position of the electrodes on the skin determine which nerve(s) is (are) stimulated.

Labour pain

A significant number of TENS machine brands have been targeted for use for labour pain, although a 1997 report of a study done by the University of Oxford said that TENS "has been shown not to be effective in postoperative and labour pain."[13] Use is documented in the attached references: in obstetric care, particularly in labour;[14].Nevertheless, there is little data on its actual efficacy, and some obstetricians maintain that it is ineffective. To learn more about TENS placement see

TENS units are also used by the BDSM community for erotic play involving electrical stimulation. See also Violet wands.


Scientific studies show that high and low frequency TENS produce their effects by activation of opioid receptors in the central nervous system[citation needed]. Specifically, high frequency TENS activates delta-opioid receptors both in the spinal cord and supraspinally (in the medulla) while low frequency TENS activates beta-opioid receptors both in the spinal cord and supraspinally[citation needed]. Further high frequency TENS reduces excitation of central neurons[citation needed] that transmit nociceptive information, reduces release of excitatory neurotransmitters (glutamate) and increases the release of inhibitory neurotransmitters (GABA) in the spinal cord, and activates muscarinic receptors centrally to produce analgesia (in effect, temporarily blocking the pain gate)[citation needed]. Low frequency TENS also releases serotonin and activates serotonin receptors in the spinal cord, releases GABA, and activates muscarinic receptors to reduce excitability of nociceptive neurons in the spinal cord[citation needed].


TENS Electrodes should never be placed:

Do not turn TENS up too high as this can cause over-stimulation which may make pain worse. There should be no muscle contraction.

TENS should also be used with caution in people with epilepsy or pregnant women (do not use over area of the uterus as the effects of electrical stimulation over the developing fetus are not known). TENS should not be used by people with cardiac pacemaker due to risk of interference and failure of their implanted device. Possible failure of these warnings can result in ventricular fibrillation.

In the situation where low frequency (or acupuncture-like) TENS is being used, it is necessary to increase the intensity of the stimulation to the point where a demonstrable muscle twitch is evident. This 2-6Hz (pulses per second) output increases the systemic release of endorphins which in turn cause pain relief.

See also


  1. Burton, C., & Maurer, D.D. (1974). Pain suppression by transcutaneous electrical nerve stimulation. IEEE Transactions on Biomedical Engineering, 21, 81–88.
  2. Jensen JE, Conn RR, Hazelrigg G, Hewett JE (1985). The use of transcutaneous neural stimulation and isokinetic testing in arthroscopic knee surgery. Am J Sports Med 13 (1): 27–33.
  3. U.S. Patent 3,817,254 
  4. Burton C (Jan 1974). Instrumentation for dorsal column stimulator implantation. Surg Neurol 2 (1): 39–40.
  5. Johnson M, Martinson, M (2006). Efficacy of electrical nerve stimulation for chronic musculoskeletal pain: A meta-analysis of randomized controlled trials. Pain 130 (1): 157–165.
  6. Nnoaham, KE, Kumbang, J (2008 Jul 16). Transcutaneous electrical nerve stimulation (TENS) for chronic pain.. Cochrane database of systematic reviews (Online) (3): CD003222.
  7. (15 February 2008)The Bone and Joint Decade 2000-2010 Task Force on Neck Pain and Its Associated Disorders: Executive Summary. Spine 33 (4S Supplement): S5–7.
  8. 8.0 8.1 Dubinsky, RM, Miyasaki, J (2010 Jan 12). Assessment: efficacy of transcutaneous electric nerve stimulation in the treatment of pain in neurologic disorders (an evidence-based review): report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology.. Neurology 74 (2): 173–6.
  9. Khadilkar, A, Odebiyi, DO; Brosseau, L; Wells, GA (2008 Oct 8). Transcutaneous electrical nerve stimulation (TENS) versus placebo for chronic low-back pain.. Cochrane database of systematic reviews (Online) (4): CD003008.
  10. Bjordal JM, Johnson MI, Ljunggreen AE (2003). Transcutaneous electrical nerve stimulation (TENS) can reduce postoperative analgesic consumption. A meta-analysis with assessment of optimal treatment parameters for postoperative pain. Eur J Pain 7 (2): 181–8.
  11. Rakel B, Frantz R (Oct 2003). Effectiveness of transcutaneous electrical nerve stimulation on postoperative pain with movement. J Pain 4 (8): 455–64.
  12. Bennett, M. I., Hughes, N. & Johnson, M. I. (2011) Methodological quality in randomised controlled trials of transcutaneous electric nerve stimulation for pain: Low fidelity may explain negative findings. Pain: 152 p. 1226-1232
  13. McQuay HJ, Moore RA, Eccleston C, Morley S, de C Williams AC (July 1997). Systematic review of outpatient services for chronic pain control. Health Technology Assessment.
  14. van der Spank JT, Cambier DC, De Paepe HM, Danneels LA, Witvrouw EE, Beerens L (Nov 2000). Pain relief in labour by transcutaneous electrical nerve stimulation (TENS). Arch. Gynecol. Obstet. 264 (3): 131–6.

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