Transcutaneous electrical nerve stimulation

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.{{cite journal | pmc=8841820 | date=2022 | last1=Huang | first1=J. | last2=Yang | first2=C. | last3=Zhao | first3=K. | last4=Zhao | first4=Z. | last5=Chen | first5=Y. | last6=Wang | first6=T. | last7=Qu | first7=Y. | title=Transcutaneous Electrical Nerve Stimulation in Rodent Models of Neuropathic Pain: A Meta-Analysis | journal=Frontiers in Neuroscience | volume=16 | doi=10.3389/fnins.2022.831413 | doi-access=free | pmid=35173577 }} 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.{{cite journal | vauthors = Johnson MI, Paley CA, Howe TE, Sluka KA | title = Transcutaneous electrical nerve stimulation for acute pain | journal = The Cochrane Database of Systematic Reviews | volume = 2021 | issue = 6 | pages = CD006142 | date = June 2015 | pmid = 26075732 | pmc = 8094447 | doi = 10.1002/14651858.CD006142.pub3 }}{{cite journal | vauthors = Gibson W, Wand BM, Meads C, Catley MJ, O'Connell NE | title = Transcutaneous electrical nerve stimulation (TENS) for chronic pain - an overview of Cochrane Reviews | journal = The Cochrane Database of Systematic Reviews | volume = 4 | pages = CD011890 | date = April 2019 | issue = 4 | pmid = 30941745 | pmc = 6446021 | doi = 10.1002/14651858.CD011890.pub3 }} Potential benefits of TENS treatment include its safety profile, relative affordability, ease of self-administration, and availability over-the-counter without a prescription. In principle, an adequate intensity of stimulation is necessary to achieve pain relief with TENS.{{cite journal | vauthors = Bjordal JM, Johnson MI, Ljunggreen AE | title = Transcutaneous electrical nerve stimulation (TENS) can reduce postoperative analgesic consumption. A meta-analysis with assessment of optimal treatment parameters for postoperative pain | journal = European Journal of Pain | volume = 7 | issue = 2 | pages = 181–188 | year = 2003 | pmid = 12600800 | doi = 10.1016/S1090-3801(02)00098-8 | s2cid = 24737458 }}{{cite journal | vauthors = Rakel B, Frantz R | title = Effectiveness of transcutaneous electrical nerve stimulation on postoperative pain with movement | journal = The Journal of Pain | volume = 4 | issue = 8 | pages = 455–464 | date = October 2003 | pmid = 14622666 | doi = 10.1067/S1526-5900(03)00780-6 }} 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.{{cite journal | vauthors = Bennett MI, Hughes N, Johnson MI | title = Methodological quality in randomised controlled trials of transcutaneous electric nerve stimulation for pain: low fidelity may explain negative findings | journal = Pain | volume = 152 | issue = 6 | pages = 1226–1232 | date = June 2011 | pmid = 21435786 | doi = 10.1016/j.pain.2010.12.009 | s2cid = 25712472 }}

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.

There is some evidence to support a benefit of using TENS in chronic musculoskeletal pain.{{cite journal | vauthors = Johnson M, Martinson M | title = Efficacy of electrical nerve stimulation for chronic musculoskeletal pain: a meta-analysis of randomized controlled trials | journal = Pain | volume = 130 | issue = 1–2 | pages = 157–165 | date = July 2007 | pmid = 17383095 | doi = 10.1016/j.pain.2007.02.007 | s2cid = 26643050 }} 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.{{cite journal | vauthors = Dubinsky RM, Miyasaki J | title = Assessment: efficacy of transcutaneous electric nerve stimulation in the treatment of pain in neurologic disorders (an evidence-based review): report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology | journal = Neurology | volume = 74 | issue = 2 | pages = 173–176 | date = January 2010 | pmid = 20042705 | doi = 10.1212/WNL.0b013e3181c918fc | doi-access = free }}{{cite journal | vauthors = Khadilkar A, Odebiyi DO, Brosseau L, Wells GA | title = Transcutaneous electrical nerve stimulation (TENS) versus placebo for chronic low-back pain | journal = The Cochrane Database of Systematic Reviews | issue = 4 | pages = CD003008 | date = October 2008 | volume = 2008 | pmid = 18843638 | pmc = 7138213 | doi = 10.1002/14651858.CD003008.pub3 | veditors = Brosseau L }}

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.{{cite journal | vauthors = Maheu E, Soriot-Thomas S, Noel E, Ganry H, Lespessailles E, Cortet B | title = Wearable transcutaneous electrical nerve stimulation (actiTENS®) is effective and safe for the treatment of knee osteoarthritis pain: a randomized controlled trial versus weak opioids | journal = Therapeutic Advances in Musculoskeletal Disease | volume = 14 | issue = | pages = 1759720X211066233 | date = 2022 | pmid = 35069809 | pmc = 8777341 | doi = 10.1177/1759720X211066233 }}

There is tentative evidence that TENS may be useful for painful diabetic neuropathy. As of 2015, the efficacy of TENS for phantom limb pain is unknown; no randomized controlled trials have been performed.{{cite journal | vauthors = Johnson MI, Mulvey MR, Bagnall AM | title = Transcutaneous electrical nerve stimulation (TENS) for phantom pain and stump pain following amputation in adults | journal = The Cochrane Database of Systematic Reviews | volume = 8 | issue = 4 | pages = CD007264 | date = August 2015 | pmid = 26284511 | pmc = 7209768 | doi = 10.1002/14651858.CD007264.pub3 }}

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.{{cite journal | vauthors = Ellrich J, Lamp S | title = Peripheral nerve stimulation inhibits nociceptive processing: an electrophysiological study in healthy volunteers | journal = Neuromodulation | volume = 8 | issue = 4 | pages = 225–232 | date = October 2005 | pmid = 22151549 | doi = 10.1111/j.1525-1403.2005.00029.x | s2cid = 22850373 }} 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,{{cite journal | vauthors = Kara M, Ozçakar L, Gökçay D, Ozçelik E, Yörübulut M, Güneri S, Kaymak B, Akinci A, Cetin A | display-authors = 6 | title = Quantification of the effects of transcutaneous electrical nerve stimulation with functional magnetic resonance imaging: a double-blind randomized placebo-controlled study | journal = Archives of Physical Medicine and Rehabilitation | volume = 91 | issue = 8 | pages = 1160–1165 | date = August 2010 | pmid = 20684895 | doi = 10.1016/j.apmr.2010.04.023 | hdl = 11511/57499 | hdl-access = free }} while the other showed that low-frequency TENS decreased shoulder impingement pain and modulated pain-induced activation in the brain.{{cite journal | vauthors = Kocyigit F, Akalin E, Gezer NS, Orbay O, Kocyigit A, Ada E | title = Functional magnetic resonance imaging of the effects of low-frequency transcutaneous electrical nerve stimulation on central pain modulation: a double-blind, placebo-controlled trial | journal = The Clinical Journal of Pain | volume = 28 | issue = 7 | pages = 581–588 | date = September 2012 | pmid = 22699130 | doi = 10.1097/AJP.0b013e31823c2bd7 | s2cid = 22274615 }}

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.{{cite journal | vauthors = McQuay HJ, Moore RA, Eccleston C, Morley S, Williams AC | title = Systematic review of outpatient services for chronic pain control | journal = Health Technology Assessment | volume = 1 | issue = 6 | pages = i–iv, 1–135 | date = July 1997 | pmid = 9483161 | doi = 10.3310/hta1060 | doi-access = free }}{{cite journal | vauthors = van der Spank JT, Cambier DC, De Paepe HM, Danneels LA, Witvrouw EE, Beerens L | title = Pain relief in labour by transcutaneous electrical nerve stimulation (TENS) | journal = Archives of Gynecology and Obstetrics | volume = 264 | issue = 3 | pages = 131–136 | date = November 2000 | pmid = 11129512 | doi = 10.1007/s004040000099 | s2cid = 1076157 }} However, more recent studies have shown that TENS was "effective for relieving labour pain, and they are well considered by pregnant participants."{{cite journal | vauthors = Báez-Suárez A, Martín-Castillo E, García-Andújar J, García-Hernández JÁ, Quintana-Montesdeoca MP, Loro-Ferrer JF | title = Evaluation of different doses of transcutaneous nerve stimulation for pain relief during labour: a randomized controlled trial | journal = Trials | volume = 19 | issue = 1 | pages = 652 | date = November 2018 | pmid = 30477529 | pmc = 6258317 | doi = 10.1186/s13063-018-3036-2 | doi-access = free }} 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.{{cite journal | vauthors = Santana LS, Gallo RB, Ferreira CH, Duarte G, Quintana SM, Marcolin AC | title = Transcutaneous electrical nerve stimulation (TENS) reduces pain and postpones the need for pharmacological analgesia during labour: a randomised trial | journal = Journal of Physiotherapy | volume = 62 | issue = 1 | pages = 29–34 | date = January 2016 | pmid = 26701166 | doi = 10.1016/j.jphys.2015.11.002 | doi-access = free }} There is tentative evidence that TENS may be helpful for treating pain from dysmenorrhoea, however further research is required.{{cite journal | vauthors = Igwea SE, Tabansi-Ochuogu CS, Abaraogu UO | title = TENS and heat therapy for pain relief and quality of life improvement in individuals with primary dysmenorrhea: A systematic review | journal = Complementary Therapies in Clinical Practice | volume = 24 | pages = 86–91 | date = August 2016 | pmid = 27502806 | doi = 10.1016/j.ctcp.2016.05.001 }}{{cite journal | vauthors = Arik MI, Kiloatar H, Aslan B, Icelli M | title = The effect of TENS for pain relief in women with primary dysmenorrhea: A systematic review and meta-analysis | journal = Explore | volume = 18 | issue = 1 | pages = 108–113 | date = 2020-08-29 | pmid = 32917532 | doi = 10.1016/j.explore.2020.08.005 | s2cid = 221637541 }}

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.{{cite journal | vauthors = Hurlow A, Bennett MI, Robb KA, Johnson MI, Simpson KH, Oxberry SG | title = Transcutaneous electric nerve stimulation (TENS) for cancer pain in adults | journal = The Cochrane Database of Systematic Reviews | issue = 3 | pages = CD006276 | date = March 2012 | volume = 2012 | pmid = 22419313 | pmc = 6669272 | doi = 10.1002/14651858.CD006276.pub3 }}{{cite journal | vauthors = Eccleston C, Fisher E, Thomas KH, Hearn L, Derry S, Stannard C, Knaggs R, Moore RA | display-authors = 6 | title = Interventions for the reduction of prescribed opioid use in chronic non-cancer pain | journal = The Cochrane Database of Systematic Reviews | volume = 11 | issue = 5 | pages = CD010323 | date = November 2017 | pmid = 29130474 | pmc = 6486018 | doi = 10.1002/14651858.CD010323.pub3 }}

Percutaneous and transcutaneous electrical nerve stimulation in the tibial nerve have been used in the treatment of overactive bladder and urinary retention.{{cite journal | vauthors = Agost-González A, Escobio-Prieto I, Pareja-Leal AM, Casuso-Holgado MJ, Blanco-Diaz M, Albornoz-Cabello M | title = Percutaneous versus Transcutaneous Electrical Stimulation of the Posterior Tibial Nerve in Idiopathic Overactive Bladder Syndrome with Urinary Incontinence in Adults: A Systematic Review | journal = Healthcare | volume = 9 | issue = 7 | pages = 879 | date = July 2021 | pmid = 34356261 | pmc = 8306496 | doi = 10.3390/healthcare9070879 | doi-access = free }}{{cite journal | vauthors = Coolen RL, Groen J, Scheepe JR, Blok BF | title = Transcutaneous Electrical Nerve Stimulation and Percutaneous Tibial Nerve Stimulation to Treat Idiopathic Nonobstructive Urinary Retention: A Systematic Review | journal = European Urology Focus | volume = 7 | issue = 5 | pages = 1184–1194 | date = September 2021 | pmid = 33268327 | doi = 10.1016/j.euf.2020.09.019 | s2cid = 226342032 | doi-access = free }} Sometimes it is also done in the sacrum.{{cite journal | vauthors = Booth J, Connelly L, Dickson S, Duncan F, Lawrence M | title = The effectiveness of transcutaneous tibial nerve stimulation (TTNS) for adults with overactive bladder syndrome: A systematic review | journal = Neurourology and Urodynamics | volume = 37 | issue = 2 | pages = 528–541 | date = February 2018 | pmid = 28731583 | doi = 10.1002/nau.23351 | s2cid = 206304402 | url = https://researchonline.gcu.ac.uk/ws/files/25192405/Booth_AcceptedPaper_Jul17_2_.pdf }} Systematic review studies have shown limited evidence on the effectiveness, and more quality research is needed.{{cite journal | vauthors = Ghavidel-Sardsahra A, Ghojazadeh M, Rahnama'I MS, Naseri A, Yazdandoost S, Khezerloo T, Seyedi-Sahebari S, Hosseinifard H, Vahed N, Mostafaei H, Salehi-Pourmehr H, Hajebrahimi S | display-authors = 6 | title = Efficacy of percutaneous and transcutaneous posterior tibial nerve stimulation on idiopathic overactive bladder and interstitial cystitis/painful bladder syndrome: A systematic review and meta-analysis | journal = Neurourology and Urodynamics | volume = 41 | issue = 2 | pages = 539–551 | date = February 2022 | pmid = 35032328 | doi = 10.1002/nau.24864 | s2cid = 247170572 }}{{cite journal | vauthors = Yang DY, Zhao LN, Qiu MX | title = Treatment for overactive bladder: A meta-analysis of transcutaneous tibial nerve stimulation versus percutaneous tibial nerve stimulation | journal = Medicine | volume = 100 | issue = 20 | pages = e25941 | date = May 2021 | pmid = 34011072 | pmc = 8137095 | doi = 10.1097/MD.0000000000025941 }} A major trial found that in a care home context transcutaneous posterior tibial nerve stimulation did not improve urinary incontinence.{{cite journal | vauthors = Booth J, Aucott L, Cotton S, Davis B, Fenocchi L, Goodman C, Hagen S, Harari D, Lawrence M, Lowndes A, Macaulay L, MacLennan G, Mason H, McClurg D, Norrie J, Norton C, O'Dolan C, Skelton D, Surr C, Treweek S | display-authors = 6 | title = Tibial nerve stimulation compared with sham to reduce incontinence in care home residents: Electric RCT | journal = Health Technology Assessment | volume = 25 | issue = 41 | pages = 1–110 | date = June 2021 | pmid = 34167637 | pmc = 8273680 | doi = 10.3310/hta25410 }}

TENS has been extensively used in non-odontogenic orofacial pain relief.{{cite journal | vauthors = Chipaila N, Sgolastra F, Spadaro A, Pietropaoli D, Masci C, Cattaneo R, Monaco A | title = The effects of ULF-TENS stimulation on gnathology: the state of the art | journal = Cranio | volume = 32 | issue = 2 | pages = 118–130 | date = April 2014 | pmid = 24839723 | doi = 10.1179/0886963413Z.00000000018 | s2cid = 22320755 }} In addition, TENS and ultra low frequency-TENS (ULF-TENS) are commonly employed in diagnosis and treatment of temporomandibular joint dysfunction (TMD). Further clinical studies are required to determine its efficacy.

A wearable neuromodulation device that delivers electrical stimulation to nerves in the wrist is now available by prescription. Worn around the wrist, it acts as a non-invasive treatment for those living with essential tremor.{{Cite web| title = De Novo Classification Request for Cala One | publisher = U.S. Food and Drug Administration |url=https://www.accessdata.fda.gov/cdrh_docs/reviews/DEN170028.pdf }} 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.{{cite journal | vauthors = Pahwa R, Dhall R, Ostrem J, Gwinn R, Lyons K, Ro S, Dietiker C, Luthra N, Chidester P, Hamner S, Ross E, Delp S | display-authors = 6 | title = An Acute Randomized Controlled Trial of Noninvasive Peripheral Nerve Stimulation in Essential Tremor | journal = Neuromodulation | volume = 22 | issue = 5 | pages = 537–545 | date = July 2019 | pmid = 30701655 | pmc = 6766922 | doi = 10.1111/ner.12930 }} In clinical trials reductions in hand tremors were reported following noninvasive median and radial nerve stimulation.{{cite journal | vauthors = Lin PT, Ross EK, Chidester P, Rosenbluth KH, Hamner SR, Wong SH, Sanger TD, Hallett M, Delp SL | display-authors = 6 | title = Noninvasive neuromodulation in essential tremor demonstrates relief in a sham-controlled pilot trial | journal = Movement Disorders | volume = 33 | issue = 7 | pages = 1182–1183 | date = July 2018 | pmid = 29663525 | pmc = 6174932 | doi = 10.1002/mds.27350 | doi-access = free }}

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.{{Cite web|title=De Novo Classification Request for Cala One|url=https://www.accessdata.fda.gov/cdrh_docs/reviews/DEN170028.pdf|archive-url=https://web.archive.org/web/20210117012552/https://www.accessdata.fda.gov/cdrh_docs/reviews/DEN170028.pdf|url-status=dead|archive-date=January 17, 2021|website=FDA}}

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.

People who have implanted electronic medical devices including pacemakers and cardiodefibrillators are not suggested to use TENS. 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. The use of TENS is likely to be less effective on areas of numb skin or decreased sensation due to nerve damage. It may also cause skin irritation due to the inability to feel currents until they are too high. There is an unknown level of risk when placing electrodes over an infection (possible spreading due to muscle contractions), but cross contamination with the electrodes themselves is of greater concern.Robertson, [https://books.google.com/books?id=XBUEfp5ZfcgC&pg=PA160 p. 160]

There are several anatomical locations where TENS electrodes are contraindicated:

• Over the eyes due to the risk of increasing intraocular pressureWatson, [https://books.google.com/books?id=1IPj7rYI2u0C&pg=PA266 p. 266]
• Transcerebrally{{cite book |url=https://books.google.com/books?id=aOjp8mbRTn4C&pg=PA232 |title=Physical Agent Modalities: Theory and Application for the Occupational Therapist |vauthors=Bracciano AG |publisher=Slack Incorporated |year=2008 |isbn=978-1556426490 |edition=2 |page=232}}
• On the front of the neck due to the risk of an acute hypotension (through a vasovagal response) or even a laryngospasmRobertson, [https://books.google.com/books?id=XBUEfp5ZfcgC&pg=PA159 p. 159]
• Through the chest using anterior and posterior electrode positions, or other transthoracic applications understood as "across a thoracic diameter"; this does not preclude coplanar applications
• Internally, except for specific applications of dental, vaginal, and anal stimulation that employ specialized TENS units
• On broken skin areas or wounds, although it can be placed around wounds
• Over a tumor or malignancy, based on in vitro experiments where electricity promotes cell growth
• Directly over the spinal column{{Citation needed|date=October 2020}}

TENS used across an artificial cardiac pacemaker or other indwelling stimulator, including across its leads, may cause interference and failure of the implanted device. Serious accidents have been recorded in cases when this principle was not observed. A 2009 review in this area suggests that electrotherapy, including TENS, is "best avoided" in patients with pacemakers or implantable cardioverter-defibrillators (ICDs). 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. The review found several reports of ICDs administering inappropriate treatment due to interference with TENS devices, but notes that the reports on pacemakers are mixed: some non-programmable pacemakers were inhibited by TENS, but others were unaffected or auto-reprogrammed.{{cite journal |display-authors=6 |vauthors=Digby GC, Daubney ME, Baggs J, Campbell D, Simpson CS, Redfearn DP, Brennan FJ, Abdollah H, Baranchuk A |date=July 2009 |title=Physiotherapy and cardiac rhythm devices: a review of the current scope of practice |journal=Europace |volume=11 |issue=7 |pages=850–859 |doi=10.1093/europace/eup102 |pmid=19411677 |doi-access=free}}

TENS should be used with caution on people with epilepsy or on pregnant people; do not use over area of the uterus, as the effects of electrical stimulation on the developing fetus are not known.Watson, [https://books.google.com/books?id=1IPj7rYI2u0C&pg=PA265 p. 265]

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.

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.{{Cite book| vauthors = Hall JE, Guyton AC |title=Guyton and Hall textbook of medical physiology|url=https://www.worldcat.org/oclc/434319356|access-date=29 March 2021|via=Worldcat|oclc=434319356}} The mechanism that will be used varies with the type of device.{{Citation needed|date=March 2022}}

The table below lists the types of devices:

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.{{cite journal | vauthors = Jensen JE, Conn RR, Hazelrigg G, Hewett JE | title = The use of transcutaneous neural stimulation and isokinetic testing in arthroscopic knee surgery | journal = The American Journal of Sports Medicine | volume = 13 | issue = 1 | pages = 27–33 | year = 1985 | pmid = 3872082 | doi = 10.1177/036354658501300105 | s2cid = 19217534 }} 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.{{Cite web |url=http://www.medicinenet.com/transcutaneous_electrical_nerve_stimulation/article.htm |title=Transcutaneous Electrical Nerve Stimulation: Side Effects & Uses}} 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.{{Citation needed|date=July 2022}} Development of the modern TENS unit is generally credited to C. Norman Shealy.Dac Teoli, Jason An (2019). [https://www.ncbi.nlm.nih.gov/books/NBK537188/ Transcutaneous Electrical Nerve Stimulation (TENS)]. StatPearls. {{PMID|30725873}}.

The first modern, patient-wearable TENS was patented in the United States in 1974.Maurer, D "Transcutaneous stimulator and stimulation method" {{US patent|3817254}}, Publication date June 18, 1974 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.{{cite journal | vauthors = Burton C | title = Instrumentation for dorsal column stimulator implantation | journal = Surgical Neurology | volume = 2 | issue = 1 | pages = 39–40 | date = January 1974 | pmid = 4810453 }} 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.{{Citation needed|date=March 2022}}

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|date=January 2021}}

Today many 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.{{Citation needed|date=January 2021}}

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.https://lethealth.us/about-us/history/

As reported, TENS has different effects on the brain. 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).{{cite journal | vauthors = Monaco A, Cattaneo R, Ortu E, Constantinescu MV, Pietropaoli D | title = Sensory trigeminal ULF-TENS stimulation reduces HRV response to experimentally induced arithmetic stress: A randomized clinical trial | journal = Physiology & Behavior | volume = 173 | pages = 209–215 | date = May 2017 | pmid = 28213205 | doi = 10.1016/j.physbeh.2017.02.014 | s2cid = 1816117 }} Further high quality studies are required to determine the effectiveness of TENS for treating dementia.{{cite journal | vauthors = Cameron M, Lonergan E, Lee H | title = Transcutaneous electrical nerve stimulation (TENS) for dementia | journal = The Cochrane Database of Systematic Reviews | volume = 2003 | issue = 3 | pages = CD004032 | date = 2003-07-21 | pmid = 12917999 | pmc = 6768999 | doi = 10.1002/14651858.CD004032 }}{{cite journal | vauthors = Abraha I, Rimland JM, Trotta FM, Dell'Aquila G, Cruz-Jentoft A, Petrovic M, Gudmundsson A, Soiza R, O'Mahony D, Guaita A, Cherubini A | display-authors = 6 | title = Systematic review of systematic reviews of non-pharmacological interventions to treat behavioural disturbances in older patients with dementia. The SENATOR-OnTop series | journal = BMJ Open | volume = 7 | issue = 3 | pages = e012759 | date = March 2017 | pmid = 28302633 | pmc = 5372076 | doi = 10.1136/bmjopen-2016-012759 }}

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.{{cite journal | vauthors = Schoenen J, Vandersmissen B, Jeangette S, Herroelen L, Vandenheede M, Gérard P, Magis D | title = Migraine prevention with a supraorbital transcutaneous stimulator: a randomized controlled trial | journal = Neurology | volume = 80 | issue = 8 | pages = 697–704 | date = February 2013 | pmid = 23390177 | doi = 10.1212/WNL.0b013e3182825055 | s2cid = 38716692 | hdl = 2268/216189 | hdl-access = free }} This was the first TENS device the FDA approved for pain prevention, as opposed to pain suppression.{{cite web|title=FDA allows marketing of first medical device to prevent migraine headaches|url=https://www.fda.gov/newsevents/newsroom/pressannouncements/ucm388765.htm|archive-url=https://web.archive.org/web/20140314213907/http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm388765.htm|url-status=dead|archive-date=March 14, 2014|work=fda.gov}}

A study performed on healthy human subjects demonstrates that repeated application of TENS can generate analgesic tolerance within five days, reducing its efficacy.{{cite journal | vauthors = Liebano RE, Rakel B, Vance CG, Walsh DM, Sluka KA | title = An investigation of the development of analgesic tolerance to TENS in humans | journal = Pain | volume = 152 | issue = 2 | pages = 335–342 | date = February 2011 | pmid = 21144659 | pmc = 3027071 | doi = 10.1016/j.pain.2010.10.040 }} The study noted that TENS causes the release of endogenous opioids, and that the analgesia is likely due to opioid tolerance mechanisms.

The pain reduction ability of TENS is unconfirmed by sufficient randomized controlled trials so far. One meta-analysis of several hundred TENS studies concluded that there was a significant overall reduction of pain intensity due to TENS, but there were too few participants and controls to be entirely certain of their validity. Therefore, the authors downgraded their confidence in the results by two levels, to low-certainty.{{cite journal | vauthors = Johnson MI, Paley CA, Jones G, Mulvey MR, Wittkopf PG | title = Efficacy and safety of transcutaneous electrical nerve stimulation (TENS) for acute and chronic pain in adults: a systematic review and meta-analysis of 381 studies (the meta-TENS study) | journal = BMJ Open | volume = 12 | issue = 2 | pages = e051073 | date = February 2022 | pmid = 35144946 | pmc = 8845179 | doi = 10.1136/bmjopen-2021-051073 }}

• Electroacupuncture
• Electrical muscle stimulation
• Erotic electrostimulation—For sexual uses of TENS devices
• Microcurrent electrical neuromuscular stimulator

{{Reflist|32em}}

• {{Cite book |vauthors=Robertson VJ, Ward A, Low J, Reed A |year=2006 |title=Electrotherapy Explained: Principles and Practice |edition=4th |publisher=Butterworth-Heinemann (Elsevier) |isbn=978-0750688437 |ref=Robertson}}
• {{Cite book |vauthors=Watson T |year=2008 |title=Electrotherapy: Evidence-based Practice |edition=12th |publisher=Elsevier Health Sciences |isbn=978-0443101793 |ref=Watson}}

• {{Cite journal |vauthors=Cekmen N, Salman B, Keles Z, Aslan M, Akcabay M |title=Transcutaneous electrical nerve stimulation in the prevention of postoperative nausea and vomiting after elective laparoscopic cholecystectomy |journal=Journal of Clinical Anesthesia |volume=19 |issue=1 |pages=49–52 |date=February 2007 |pmid=17321927 |doi=10.1016/j.jclinane.2006.05.025 }}
• {{Cite journal |vauthors=Gan LS, Prochazka A, Bornes TD, Denington AA, Chan KM |title=A new means of transcutaneous coupling for neural prostheses |journal=IEEE Transactions on Bio-Medical Engineering |volume=54 |issue=3 |pages=509–517 |date=March 2007 |pmid=17355064 |doi=10.1109/TBME.2006.886664 |s2cid=9568471 }}
• {{Cite journal |vauthors=Ozawa M, Tsuchiyama K, Gomi R, Kurosaki F, Kawamoto Y, Aiba S |title=Neuroselective transcutaneous electric stimulation reveals body area-specific differences in itch perception |journal=Journal of the American Academy of Dermatology |volume=55 |issue=6 |pages=996–1002 |date=December 2006 |pmid=17097397 |doi=10.1016/j.jaad.2006.08.032 }}
• {{Cite book |vauthors=Vrbová G, Hudlicka O, Schaefer Centofanti K |title=Application of Muscle/Nerve Stimulation in Health and Disease |publisher=Springer |year=2008 |isbn=978-1402082320}}

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Category:Pain management