What Is TENS Unit Therapy?

Transcutaneous Electrical Nerve Stimulation (TENS) is predominantly used for the treatment of nerve related pain conditions. A TENS machine is generally considered safe, although it is not used in individuals who have a pacemaker or who are in the first weeks of pregnancy. By definition, the unit applies electrical stimulation transcutaneously across a broad range of anatomy. Electrical stimulation was first used in ancient Rome to relieve pain by using electrical fish from the sea. Later, a variety of other devices were used to treat headaches and other pain. There are several anatomical locations where the use of the units is contraindicated.  A TENS unit should not be used over the eyes, through the chest, on broken skin, over a tumor, directly over the spinal cord, or internally.

How Is TENS Unit Therapy Performed?

Typically, the TENS unit is battery operated and introduces an electrical stimulation at high frequency and with an intensity that will not trigger motor contractions. The physician can adjust the pulse, frequency, and intensity for specific conditions. The way in which the TENS unit modulates pain reception is still not completely understood.  Theoretically, it may block the perception of pain or increase the secretion of endorphins in the central nervous system. Both of these factors will reduce pain perception and improve treatment. Although primarily used for pain control, this type of electrical stimulation has also been demonstrated to improve circulation locally and either reduce or completely eliminate muscle spasms.

Treatment is initiated when the electrodes are placed over the skin in the area where the patient is experiencing pain. These electrodes are connected by a wire to a small unit that generates the electrical stimulation. The unit may produce a tingling sensation where the electrodes are placed on the skin. However, generally there are very few other side effects from the unit.  A TENS unit can be used at home for pain control. In these cases patients are given instruction by their physical therapist or physician as to how to place the electrodes, how to correctly input the electrical frequency and pulse strength, how to determine how long the treatment should be given, and how often it should be used.

Conditions Related To TENS Unit Therapy

The TENS unit is used for a noninvasive nerve stimulation to reduce chronic and acute pain.  There is evidence that the unit is used successfully in individuals who suffer musculoskeletal pain post-operatively and in individuals who have osteoarthritis. It has also been shown to potentially be useful for people suffering from diabetic neuropathy.  In a study combining the use of a TENS device with intra-articular hyaluronic acid injections in individuals who suffer from osteoarthritis, researchers found statistically significant pain relief in the first months, which continued through the six month follow-up.  The TENS unit has also been effective in pain control over the use of placebos in individuals who suffer from osteoarthritis.

In one meta-analysis researchers found evidence that there are both peripheral and central nervous system mechanisms that impact the analgesic effect of TENS unit therapy.  Results found that the intensity of stimulation is a critical factor in the success rate of pain treatment using a TENS unit.  Successful treatment using electrical stimulation for the relief of musculoskeletal pain was consistently demonstrated for both acute and post-operative conditions.

In another study, the unit was evaluated for the relief of pain during labor. Seventeen different studies were assessed with a total of 1,466 women participating. The results were not as positive as those using individuals with other types of chronic or acute pain. Pain scores were similar in women who use the unit and in those who did not. There was some evidence that women using the TENS unit had less severe pain, but the results were not consistent across the studies. The TENS unit did not seem to have an effect on the length of labor, interventions used or the ultimate well-being of mother and baby.

Other uses for transcutaneous electrical stimulation include increasing the range of motion for individuals who suffer from adhesive capsulitis (frozen shoulder).  Research demonstrated that the TENS unit increased the range of motion more than heat, manipulation, and exercise. Significant advancements in technology have also led to the introduction of an innovative device that offers an external cranial neuro-stimulation technique for treatment and prevention of migraines.  In studies where participants used this device, medication use fell an impressive 37% with no significant side effects or contraindications from the device.

Conclusion

A TENS unit is a transcutaneous electrical nerve stimulator used predominantly for the treatment of pain and is generally considered safe.  Theoretically the unit will block the perception of pain or increase the secretion of endorphins.  The TENS unit has also demonstrated success in reducing or eliminating muscle spasms.

The electrical stimulation is delivered through electrodes taped over the skin in the area where the patient is experiencing pain.  This noninvasive nerve stimulation has had success relieving pain in individuals who suffer from osteoarthritis, diabetic neuropathy, musculoskeletal pain, post-operative pain, adhesive capsulitis and, most recently, in the prevention and treatment of migraines. The TENS unit has a significantly a low side effect profile and very few contraindications for use, making it a good pain management option for many people.

References

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