TENS, by definition, covers the complete range of transcutaneously applied currents used for nerve excitation, but the term is often used with a more restrictive intent, namely, to describe the kind of pulses produced by portable stimulators used to reduce pain.
[2] Transcutaneous electrical nerve stimulation is a commonly used treatment approach to alleviate acute and chronic pain by reducing the sensitization of dorsal horn neurons, elevating levels of gamma-aminobutyric acid and glycine, and inhibiting glial activation.
[3] Many systematic reviews and meta-analyses assessing clinical trials looking at the efficacy of TENS for different sources of pain, however, have been inconclusive due to a lack of high-quality and unbiased evidence.
[4][5] Potential benefits of TENS treatment include its safety profile, relative affordability, ease of self-administration, and availability over-the-counter without a prescription.
[10][11] Another study examining knee osteoarthritis patients found that TENS demonstrated efficacy and a better safety profile relative to weak opiates.
[14] Two other studies used functional magnetic resonance imaging (fMRI): one showed that high-frequency TENS produced a decrease in pain-related cortical activations in patients with carpal tunnel syndrome,[15] while the other showed that low-frequency TENS decreased shoulder impingement pain and modulated pain-induced activation in the brain.
[21][22] Non-pharmacological treatment options for people experiencing pain caused by cancer are much needed, however, it is not clear from the weak studies that have been published if TENS is an effective approach.
[27][28][29] A major trial found that in a care home context transcutaneous posterior tibial nerve stimulation did not improve urinary incontinence.
[31] In addition, TENS and ultra low frequency-TENS (ULF-TENS) are commonly employed in diagnosis and treatment of temporomandibular joint dysfunction (TMD).
[4] In addition, caution should be taken before using TENS in those who are pregnant, have epilepsy, have an active malignancy, have deep vein thrombosis, have skin that is damaged, or are frail.
They add that "there is no consensus and it may be possible to safely deliver these modalities in a proper setting with device and patient monitoring", and recommend further research.
[40] TENS should be used with caution on people with epilepsy or on pregnant women; do not use over area of the uterus, as the effects of electrical stimulation on the developing fetus are not known.
[citation needed] The table below lists the types of devices: Electrical stimulation for pain control was used in ancient Rome, in AD 63.
[49] It was initially used for testing the tolerance of chronic pain patients to electrical stimulation before implantation of electrodes in the spinal cord dorsal column.
[citation needed] A number of companies began manufacturing TENS units after the commercial success of the Medtronic device became known.
The neurological division of Medtronic, founded by Don Maurer, Ed Schuck and Charles Ray, developed a number of applications for implanted electrical stimulation devices for treatment of epilepsy, Parkinson's disease, and other disorders of the nervous system.
[citation needed] Beginning in the late 1970s, in the USSR as part of their space program further research was conducted into electronic pain reduction devices.
[14] A randomized controlled trial in 2017 shown that sensory ULF-TENS applied on the skin proximally to trigeminal nerve, reduced the effect of acute mental stress assessed by heart rate variability (HRV).
[53][54] A head-mounted TENS device called Cefaly was approved by the United States Food and Drug Administration (FDA), in March 2014, for the prevention of migraine attacks.
[56] A study performed on healthy human subjects demonstrates that repeated application of TENS can generate analgesic tolerance within five days, reducing its efficacy.