How Transcutaneous Electrical Nerve Stimulation Works to Treat Acute and Chronic Pain

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About Transcutaneous Electrical Nerve Stimulation

TENS is a type of electroanalgesia, a term which describes the use of electric current to relieve acute and chronic pain. TENS can be used to treat pain caused by arthritis, tendonitis, bursitis, and other types of body inflammation, as well as cancer, nerve damage, post-surgical pain and muscular pain. It should be noted, however, that while TENS can help relieve pain, it is not a curative treatment, and it cannot cure the underlying cause of the pain.

The theory behind TENS was developed in the 1960s by Dr. Ronald Melzac and Dr. Patrick Wall, who called their idea the Gate Control Theory. According to this theory, stimulation of nerves via mild electrical current causes a gate-like mechanism to close in the spinal cord, preventing the transmission of pain signals to the brain.

In the 1970s, TENS was used as an alternative therapy for pain management. These days, it has become so widely accepted that it is one of the few alternative therapies to have received approval from the FDA.

How Does TENS Work to Relieve Pain?

The TENS unit is simple in design, consisting of a small battery-powered electrical unit and electrodes connected via long wires. The unit generally has two or more electrodes. During a TENS treatment the electrodes are placed on the skin, at or near the location of the pain. The unit is then switched on, causing a mild electrical current to pass through the electrodes to the skin. For most people the sensation is of warmth, or a mild tingling.

A typical TENS treatment lasts between five and fifteen minutes, and when the user owns a home TENS unit, treatments can be applied as often as he or she desires. In addition the user can opt to change the intensity of the electrical current depending on his or her needs.

As Dr. Ronald Melzac and Dr. Patrick Wall theorized in the 1960s, recent lab studies indicate that TENS works by limiting the transmission of pain signals via a central nervous system “gate” mechanism.

It is believed that this “gate” is normally shut, and is opened as a response to pain. For people with acute or chronic pain disorders the gate is permanently open, or can open as an abnormal response to certain stimuli. TENS therapy temporarily causes the gate to return to its normal closed position by delivering abnormal electrical stimulation. Essentially, the central nervous system shuts off pain transmission temporarily as a reaction to the nerves which are over-excited due to TENS.

TENS Therapy Safety Issues

Transcutaneous electrical nerve stimulation is generally regarded as safe; however there are some safety issues to be aware of when using a TENS unit.

  • TENS electrodes should never be used in the mouth, near the eyes, on the temples, on the front of the neck, near the heart, or on broken skin. Use of electrodes in these locations might result in electric shocks of dangerous intensity, or which can potentially disturb heart or brain function.

  • Women who are pregnant should avoid using TENS, because the long-term effects of this therapy on a fetus are unknown. If the use of TENS cannot be avoided, the electrodes should never be placed anywhere near the uterus.

  • People with a cardiac condition, particularly those who use a pacemaker or internal defibrillator, should not use TENS, due to the possibility of inducing a potentially fatal cardiac arrythmia.

  • TENS should not be used to replace medical treatment. For example, someone who is using TENS to treat pain associated with cancer should not use TENS as a replacement for curative treatment when such treatment is possible.


American Cancer Society: Transcutaneous Electrical Nerve Stimulation

Vladimir Kaye, MD, for eMedicine: Transcutaneous Electrical Nerve Stimulation