What is TENS?
Transcutaneous electrical nerve stimulation (TENS) is a drug-free method of pain relief that has been used to treat a wide variety of muscle and joint problems, as well as many other painful conditions. TENS uses electrical impulses to stimulate the nerve endings at or near the site of pain, diminishing the pain and replacing it with a tingling or massagelike sensation.
TENS can be used in a health-care setting, but most often the patient uses it at home.
How does TENS work?
Researchers still are not certain exactly how TENS works. The two explanations suggested most often are that electrical stimulation of the nerves blocks the pain sensation and that TENS triggers the release of the body’s natural painkillers, called endorphins.
A TENS device consists of an adjustable power unit and electrodes that attach to the power unit via wires.
- The typical power unit is small — about the size of a beeper or a cell phone. Controls allow the patient to adjust the intensity of the stimulation. Some units also adjust for either high-frequency or low-frequency stimulation. Frequency is a measure of the number of electromagnetic waves in a given time period.
- Electrodes come in a variety of shapes. They usually are self-adhesive and made of cloth or foam. A gel is applied under the electrode to improve the flow of current.
Before beginning treatment, the patient must put the electrodes in place — usually on top of or next to the painful area. Patients can experiment with different locations for the electrodes to see what provides the best pain relief. In some cases, it may be more effective to position the electrodes on top of a related nerve or a site that is considered to be a trigger point or acupuncture point for the painful area.
Are there different types of TENS?
Electrical stimulation can be used in the following ways:
- Conventional TENS — This is the most typical type of treatment. It uses a high stimulation frequency, but the intensity of the electrical stimulus is low. Patients usually leave the electrodes on for long periods of time, turning them on and off at intervals. A typical treatment might last 30 minutes, but the length can vary depending on patient needs. Pain often is relieved only while the treatment is under way, but the relief may last longer.
- Acupuncturelike TENS — In this case, the stimulation frequency is low, but the electrical impulse is quite intense. Some patients find this more effective or longer lasting than conventional TENS. Other patients find acupuncturelike TENS too uncomfortable.
- Percutaneous electrical nerve stimulation — PENS, as it is known, is a combination of acupuncture and electrical stimulation. Instead of electrodes, PENS uses needles to penetrate the skin and deliver the electrical stimulation.
How effective is TENS?
TENS has been used in patients with muscular pain, osteoarthritis, rheumatoid arthritis, sciatica, pain after surgery and other conditions.
Studies have shown varying results as to how well TENS works, what types of pain it can best relieve and how long the relief lasts. Many people have found TENS helpful, however, and many doctors recommend it as part of an overall pain-management program.
What are the advantages and disadvantages of TENS?
- TENS does not involve the use of drugs. For patients who find it helpful, TENS can reduce drug use for pain relief and thus reduce the side effects of drugs.
- Some patients also like TENS because they are in control and can adjust the length and intensity of treatment.
- TENS can cause skin irritation. This often can be avoided by changing the type of gel or electrode used.
- TENS is not always effective.
- Electrical stimulation should not be used on the front of the neck. This can be dangerous because stimulation of nerves in this area can affect the rhythm of the heart.
- People who wear pacemakers should ask their doctors about whether TENS is safe for them. TENS can interfere with the operation of some types of pacemakers.
- It is not clear whether TENS is safe for pregnant women.