Dr. Martin's notes

Tuesday January 31, 2017

Transcutaneous electrical nerve stimulation (TENS):

The use of electrical current to block the sensation of pain to a given area of the body.

This modality is used primarily for pain control. Electrodes are placed on the skin, over the painful area to block the sensation of chronic or acute pain. The use of transcutaneous electrical nerve stimulation (TENS) causes a muscle contraction, so this modality must be used with caution if it is applied immediately after an injury. (TENS does not have to be administered continually to be effective. Often, a 30-minute to one-hour application will relieve pain for hours after the treatment. However, stimulation of the muscle must be controlled or it will cause undesired tension. The use of TENS therapy may allow a patient to perform therapeutic exercise without pain. The TENS electrodes must not be placed over the carotid arteries, metal implants, high fluid areas, the abdomen of a pregnant woman, or where there is a pacemaker. Additional contraindications include undiagnosed pain, hypertension, diabetes, or an allergic reaction to the tape, gel, or electrodes.

TENS by definition covers the complete range of transcutaneously applied currents although the term is often used with a more restrictive intent, namely to describe the kind of pulses produced by portable stimulators used to treat pain. The unit is usually connected to the skin using two or more electrodes.

TENS is a non-invasive, safe nerve stimulation intended to reduce pain, both acute and chronic. While controversy exists as to its effectiveness in the treatment of chronic pain, a number of systematic reviews or meta-analyses have confirmed its effectiveness for postoperative pain, osteoarthritis, and chronic musculoskeletal pain.

Scientific studies show that high and low frequency TENS produce their effects by activation of opioid receptors in the central nervous system. Specifically, high frequency TENS activates delta-opioid receptors both in the spinal cord and supraspinally (in the medulla) while low frequency TENS activates beta-opioid receptors both in the spinal cord and supraspinally. Further high frequency TENS reduces excitation of central neurons that transmit nociceptive information, reduces release of excitatory neurotransmitters (glutamate) and increases the release of inhibitory neurotransmitters (GABA) in the spinal cord, and activates muscarinic receptors centrally to produce analgesia (in effect, temporarily blocking the pain gate.