Transcutaneous electrical nerve stimulation

Pain 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. 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. Potential benefits of TENS treatment include its safety profile, relative affordability, ease of self-administration, and availability over-the-counter without a prescription. An analysis of treatment fidelity—meaning that the delivery of TENS in a trial was in accordance with current clinical advice, such as using "a strong but comfortable sensation" and suitable, frequent treatment durations—showed that higher-fidelity trials tended to have a positive outcome. Repeated use of TENS at the same intensity and frequency settings may lead to analgesic tolerance, this effect may be reduced by varying stimulation frequency or increasing intensity. Recent clinical trials indicate that TENS may only be effective for a subset of patients, with approximately 44% of individuals experience a meaningful reduction in pain. Compared to pharmacological drug treatments, TENS can have a similar effectiveness in some patients while presenting a lower risk of adverse effects. Acute pain For people with recent-onset pain i.e., fewer than three months, such as pain associated with surgery, trauma, and medical procedures, TENS may be better than placebo in some cases. The evidence of benefit is very weak, though. Results from a task force on neck pain in 2008 found no clinically significant benefit of TENS for the treatment of neck pain when compared to placebo. A 2010 review did not find evidence to support the use of TENS for chronic low back pain. Another study examining knee osteoarthritis patients found that TENS demonstrated efficacy and a better safety profile relative to weak opiates. Given the age, comorbidity frequency, tendency toward polypharmacy, and sensitivity to adverse reactions among individuals most frequently reporting osteoarthritis, TENS could be a non-pharmacological alternative to analgesics in the management of knee osteoarthritis pain. Neuropathy and phantom limb pain There is tentative evidence that TENS may be useful for painful diabetic neuropathy. A few studies have shown objective evidence that TENS may modulate or suppress pain signals in the brain. One used evoked cortical potentials to show that electric stimulation of peripheral A-beta sensory fibers reliably suppressed A-delta fiber nociceptive (pain perception) processing. 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, while the other showed that low-frequency TENS decreased shoulder impingement pain and modulated pain-induced activation in the brain. Labor and menstrual pain Early studies found that TENS "has been shown not to be effective in postoperative and labour pain." These studies also had questionable ability to truly blind the patients. However, more recent studies have shown that TENS was "effective for relieving labour pain, and they are well considered by pregnant participants." One study also showed that there was a significant change in laboring individuals' time to request analgesia such as an epidural. The group with the TENS waited five additional hours relative to those without TENS. Both groups were satisfied with the pain relief that they had from their choices. No maternal, infant, or labor problems were noted. There is tentative evidence that TENS may be helpful for treating pain from dysmenorrhoea, however further research is required. Cancer pain 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. Bladder function Percutaneous and transcutaneous electrical nerve stimulation in the tibial nerve have been used in the treatment of overactive bladder and urinary retention. Sometimes it is also done in the sacrum. Systematic review studies have shown limited evidence on the effectiveness, and more quality research is needed. A major trial found that in a care home context transcutaneous posterior tibial nerve stimulation did not improve urinary incontinence. Dentistry TENS has been extensively used in non-odontogenic orofacial pain relief. In addition, TENS and ultra low frequency-TENS (ULF-TENS) are commonly employed in diagnosis and treatment of temporomandibular joint dysfunction (TMD). The stimulator has electrodes that are placed circumferentially around a patient's wrist. Positioning the electrodes on generally opposing sides of the target nerve can result in improved stimulation of the nerve. In clinical trials reductions in hand tremors were reported following noninvasive median and radial nerve stimulation. Transcutaneous afferent patterned stimulation (TAPS) is a tremor-customized therapy, based on the patient's measured tremor frequency, and is delivered transcutaneously to the median and radial nerves of a patient's wrist. The patient specific TAPS stimulation is determined through a calibration process performed by the accelerometer and microprocessor on the device. The Cala ONE delivers TAPS in a wrist-worn device that is calibrated to treat tremor symptoms. Cala ONE received de novo FDA clearance in April 2018 for the transient relief of hand tremors in adults with essential tremor and is currently marketed as Cala Trio. == Contraindications ==

People who have implanted electronic medical devices including pacemakers and cardiodefibrillators are not suggested to use TENS. There are several anatomical locations where TENS electrodes are contraindicated: • Over the eyes due to the risk of increasing intraocular pressure • Transcerebrally • On the front of the neck due to the risk of an acute hypotension (through a vasovagal response) or even a laryngospasm • Through the chest using anterior and posterior electrode positions, Pregnancy TENS should be used with caution on pregnant people; do not use over area of the uterus, as the effects of electrical stimulation on the developing fetus are not known. == Side effects ==

Overall, TENS has been found to be safe compared with pharmaceutical medications for treating pain. Potential side effects include skin itching near the electrodes and mild redness of the skin (erythema). Some people also report that they dislike the sensation associated with TENS. == Device types ==

The TENS device acts to stimulate the sensory nerves and a small portion of the peripheral motor nerves; the stimulation causes multiple mechanisms to trigger and manage the sense of pain in a patient. TENS operates by two main mechanisms: it stimulates competing sensory neurons at the pain perception gate, and it stimulates the opiate response. The mechanism that will be used varies with the type of device. The table below lists the types of devices: ==History==

Electrical stimulation for pain control was used in ancient Rome, in AD 63. It was reported by Scribonius Largus that pain was relieved by standing on an electrical fish at the seashore. In the 16th through the 18th centuries various electrostatic devices were used for headache and other pains. Benjamin Franklin was a proponent of this method for pain relief. In the 19th century a device called the electreat, along with numerous other devices were used for pain control and cancer cures. Only the electreat survived into the 20th century, but was not portable, and had limited control of the stimulus. Modern Development of the modern TENS unit has been credited to C. Norman Shealy, an American neurosurgeon. The practice dates back to earlier work on neurostimulation. Shealy aimed to use it to treat migraines, back pain, and gout. 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. The electrodes were attached to an implanted receiver, which received its power from an antenna worn on the surface of the skin. Although intended only for testing tolerance to electrical stimulation, many of the patients said they received so much relief from the TENS itself that they never returned for the implant. 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. Beginning in the late 1970s, in the USSR as part of their space program further research was conducted into electronic pain reduction devices. Dr. Alexander Karasev developed scenar (or skenar) devices, and later in the early 2000s cosmodic devices. Each of these device types uses the fundamental technique of reading electrical signals in the skin, analyzing the signals, and returning therapeutic electrical pulses into the nerves. He terms the TENS devices first generation electronic pain relief devices, scenar devices second generation devices, cosmodic devices as third generation devices, and the D.O.V.E. (Device Organizing Vital Energy) device as an advanced second generation device which automatically incorporates some cosmodic therapeutic features. == Research ==

As reported, TENS has different effects on the brain. Further high quality studies are required to determine the effectiveness of TENS for treating dementia. 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. The Cefaly device was found effective in preventing migraine attacks in a randomized sham-controlled trial. This was the first TENS device the FDA approved for pain prevention, as opposed to pain suppression. A study performed on healthy human subjects demonstrates that repeated application of TENS can generate analgesic tolerance within five days, reducing its efficacy. The study noted that TENS causes the release of endogenous opioids, and that the analgesia is likely due to opioid tolerance mechanisms. == Related treatments ==

Some people confuse TENS with electrical muscle stimulation (EMS). EMS and TENS devices look similar, with both using long electric lead wires and electrodes. TENS is for blocking pain, where EMS is for stimulating muscles. ==See also==