Transcutaneous Electrical Nerve Stimulation (TENS)

Transcutaneous Electrical Nerve Stimulation (TENS)

Transcutaneous electrical nerve stimulation (TENS) involves utilizing electric current generated by a device to activate nerves for therapeutic aims. TENS encompasses the entire spectrum of currents applied transcutaneously for nerve stimulation, though the term is often employed in a narrower sense to describe the pulses generated by portable stimulators for pain management. Typically, the device is affixed to the skin using two or more electrodes.

A standard battery-operated TENS unit can adjust pulse width, frequency, and intensity. Generally, TENS is administered at high frequency (>50 Hz) with an intensity below that causing muscle contraction (sensory level) or at low frequency (<10 Hz) with an intensity resulting in muscle contraction. The efficacy of TENS for pain relief is a subject of debate.

TENS is a non-invasive, low-risk nerve stimulation technique aimed at alleviating both acute and chronic pain. Disagreement persists regarding its effectiveness in treating chronic pain.

Scientific research indicates that both high and low frequency TENS exert their effects by activating opioid receptors in the central nervous system. Specifically, high frequency TENS activates delta-opioid receptors in the spinal cord and supraspinally (in the medulla), while low frequency TENS activates beta-opioid receptors in the spinal cord and supraspinally.

Moreover, high frequency TENS reduces the excitation of central neurons transmitting pain signals, diminishes the release of excitatory neurotransmitters (glutamate), enhances the release of inhibitory neurotransmitters (GABA) in the spinal cord, and centrally activates muscarinic receptors to induce analgesia (essentially blocking the pain signal temporarily). Low frequency TENS also releases serotonin, activates serotonin receptors in the spinal cord, releases GABA, and activates muscarinic receptors to reduce the excitability of pain-transmitting neurons in the spinal cord.

TENS should not be used over an artificial cardiac pacemaker (or other implanted stimulator, including across its leads) due to the risk of interference and malfunction of the implanted device. Incidents of serious accidents have been documented when this precaution was disregarded.

Exercise caution when applying TENS to areas with numbness or reduced sensation, as it may be less effective due to nerve damage. Additionally, it may cause skin irritation because the currents cannot be felt until they reach a high level. Electrodes should not be placed over an infection due to the potential for spreading caused by muscle contractions, and the risk of cross-contamination with the electrodes themselves is of greater concern. TENS should also be used cautiously in individuals with epilepsy or pregnant women; avoid applying it over the area of the uterus, as the effects of electrical stimulation on the developing fetus are unknown.