Transcutaneous Electrical Nerve Stimulation also known as TENS, is a noninvasive and straightforward technique that is quickly becoming a trend in pain therapy.
It is widely used in physiotherapy and rehabilitation, and non-technical population is also growing interested in this technology. It is an exciting approach to improve the occurrence of acute pain in cases of joint dysfunction, musculoskeletal pain, and other conditions such as dysmenorrhea and labor.
This technique was introduced in the 1970s. It was initially thought to be a screening technique to evaluate who will benefit from implants of electrical stimulators to relieve pain. However, several patients started to experience significant pain relief after using this screening method. In the end, fewer electrical stimulators were implanted because patients using TENS no longer needed them.
But is TENS effective in reducing pain symptoms according to research? Is it safe? Are there any side effects we should know about before trying this procedure?
What is Transcutaneous Electrical Nerve Stimulation?
By definition, Transcutaneous Electrical Nerve Stimulation is a noninvasive procedure applied directly to the intact skin. Through a simple and battery-powered device, TENS delivers pulsed electrical current across the skin and stimulates peripheral nerves to inhibit pain stimuli. This is achieved by using a series of electrodes attached to the skin. It is considered to be a safe and inexpensive technique that patients can administer themselves according to easy-to-follow and simple instructions and safety guidelines.
For many years, similar forms of electricity were used for pain relief, and this numbing effect was referred to as electroanalgesia in 1965. According to electroanalgesia theories, there are excitatory and inhibitory neurons in the dorsal horn of the spinal cord. Pain stimuli travel to the brain through the dorsal horn, and other stimuli such as pressure and electrical currents use the same path and overlap with pain sensation, causing an inhibitory effect.
There are various forms of TENS, according to each patient and type of pain. We can choose a different pulse frequency, amplitude, and duration, and it is possible to try new electrode placement sites. There is also a modality named acupuncture-like TENS or AL-TENS, which uses acupuncture needles to deliver electrical currents through the skin into deeper tissues.
Benefits of Transcutaneous Electrical Nerve Stimulation
TENS is not only an interesting theory. It also has a clinical application, and it works to improve pain symptoms in various settings. It is not likely to replace painkillers and other treatment approaches, but it is a suitable complementary treatment to enhance the quality of life of patients who need to take NSAIDs and perhaps electrical muscle stimulation to manage their symptoms.
We can count several benefits of TENS, both in the short-term and the long-term:
- It is a standard procedure in physical therapy: TENS is commonly used by physical therapists to improve pain symptoms and regain the function of the joint and the muscle in cases of rehabilitation. In these cases, TENS has an acute effect in reducing pain symptoms, but may also help patients recover faster from various causes of chronic pain through a combination of TENS, functional training and exercise.
- Reduces hospital stays: Studies show that TENS allows patients with chronic pain to increase their levels of physical activity and may be helpful to reduce hospital stay in many cases. This is particularly the case of postoperative pain after thoracic surgery, chronic low back pain, and joint pain in patients with arthritis. TENS has been found to speed up recovery and improve pulmonary function in postoperative patients.
- Improves the patient’s tolerance to physical activity: Joint pain often leads to a low tolerance to exercise, which in turn may aggravate joint pain in a vicious cycle. By reducing the perception of pain, TENS improves the joint function and allows patients to tolerate physical activity and other forms of physical therapy that will ultimately improve their quality of life in the long run.
- It works in combination with certain medications: Certain studies have shown that TENS in combination with clonidine or morphine reduces primary hyperalgesia, a condition that is difficult to manage with TENS alone. This probably results from a synergistic interaction between endogenous opioids and alpha-2-adrenergic agonist drugs. By using a combination of these drugs and TENS, patients will be able to reduce the dose of opioid medications and their side effects.
- The effect is maintained for up to 4 weeks: According to a study on the application of TENS in osteoarthritis, there was a reduction of pain in patients receiving TENS with or without physical exercise, and this decrease in the sensation of pain was maintained in the 4-week follow-up.
What you need to know before using TENS
TENS is an excellent therapy to induce analgesia in various types of pain. However, there are certain effects of this therapy you should know about before trying this pain therapy modality:
- It produces tolerance and cross-tolerance: After applying TENS daily for a long time, it is possible to develop tolerance to the treatment. On the long run, it would become ineffective in producing the same analgesic effect. TENS has a cross-tolerance impact on opioid therapy, and repeated use will render morphine ineffective to control pain symptoms. Similarly, patients who have become tolerant to morphine are not likely to find much relief after TENS.
- Pain, tingling, or burning at the electrode site: In some cases, it is possible to feel some pain, tingling or burning sensation in the skin at the site of electrode placement. This effect is often reported right after TENS session, and it is self-limited.
- Some people may not tolerate TENS: In some studies, patients were unable to tolerate TENS and reported discomfort during electrical stimulation. This is not common and was only reported in 2 out of 48 participants in one study and 1 out of 13 participants in a second study.
Transcutaneous Electrical Nerve Stimulation (TENS) remains a safe and effective way to improve the symptoms in patients with joint, chronic back pain, and even periodontal and other types of pain. It is considered by a recent Cochrane review as a potential treatment option, and it is marked as a safe alternative that’s inexpensive and readily available as an over-the-counter measure.
Johnson, M. I., Paley, C. A., Howe, T. E., & Sluka, K. A. (2015). Transcutaneous electrical nerve stimulation for acute pain. Cochrane database of systematic reviews, (6).
Murina, F., & Di Francesco, S. (2015). Transcutaneous Electrical Nerve Stimulation. In Electrical Stimulation for Pelvic Floor Disorders (pp. 105-117). Springer, Cham.
Sluka, K. A., & Walsh, D. (2003). Transcutaneous electrical nerve stimulation: basic science mechanisms and clinical effectiveness. The Journal of pain, 4(3), 109-121.