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== Medical uses ==
[[File:Neuro-ms.png|thumb|285x285px|A magnetic coil is positioned on the patient's head.<ref name=":0" />]]
TMS does not require surgery or electrode implantation.
Its use can be diagnostic and/or therapeutic. Effects vary based on frequency and intensity of the magnetic pulses as well as the length of treatment, which dictates the total number of pulses given.<ref>{{Cite journal|date=2015-09-01|title=Basic principles of transcranial magnetic stimulation (TMS) and repetitive TMS (rTMS)|journal=Annals of Physical and Rehabilitation Medicine|language=en|volume=58|issue=4|pages=208–213|doi=10.1016/j.rehab.2015.05.005|issn=1877-0657|doi-access=free|last1=Klomjai|first1=Wanalee|last2=Katz|first2=Rose|last3=Lackmy-Vallée|first3=Alexandra|pmid=26319963}}</ref> TMS treatments are approved by the FDA in the US and by NICE in the UK for the treatment of depression and are predominantly provided by private clinics. TMS stimulates cortical tissue without the pain sensations produced in [[transcranial direct-current stimulation|transcranial electrical stimulation]].<ref>
=== Diagnosis ===
TMS can be used clinically to measure activity and function of specific brain circuits in humans, most commonly with single or paired magnetic pulses.<ref name=diagnostic1 /> The most widely accepted use is in measuring the connection between the [[primary motor cortex]] of the [[central nervous system]] and the [[peripheral nervous system]] to evaluate damage related to past or progressive neurologic insult.<ref name=diagnostic1 /><ref>{{cite journal | vauthors = Rossini PM, Rossi S | title = Transcranial magnetic stimulation: diagnostic, therapeutic, and research potential | journal = Neurology | volume = 68 | issue = 7 | pages = 484–488 | date = February 2007 | pmid = 17296913 | doi = 10.1212/01.wnl.0000250268.13789.b2 | s2cid = 19629888 }}</ref><ref name="Dimyan">{{cite journal | vauthors = Dimyan MA, Cohen LG | title = Contribution of transcranial magnetic stimulation to the understanding of functional recovery mechanisms after stroke | journal = Neurorehabilitation and Neural Repair | volume = 24 | issue = 2 | pages = 125–135 | date = February 2010 | pmid = 19767591 | pmc = 2945387 | doi = 10.1177/1545968309345270 }}</ref><ref name="Nowak">{{cite journal | vauthors = Nowak DA, Bösl K, Podubeckà J, Carey JR | title = Noninvasive brain stimulation and motor recovery after stroke | journal = Restorative Neurology and Neuroscience | volume = 28 | issue = 4 | pages = 531–544 | year = 2010 | pmid = 20714076 | doi = 10.3233/RNN-2010-0552 }}</ref> TMS has utility as a diagnostic instrument for [[myelopathy]], [[amyotrophic lateral sclerosis]], and [[multiple sclerosis]].<ref name="Chen2008">{{cite journal |last1=Chen |first1=Robert |last2=Cros |first2=Didier |last3=Curra |first3=Antonio |last4=Di Lazzaro |first4=Vincenzo |last5=Lefaucheur |first5=Jean-Pascal |last6=Magistris |first6=Michel R. |last7=Mills |first7=Kerry |last8=Rösler |first8=Kai M. |last9=Triggs |first9=William J. |last10=Ugawa |first10=Yoshikazu |last11=Ziemann |first11=Ulf |title=The clinical diagnostic utility of transcranial magnetic stimulation: Report of an IFCN committee |journal=Clinical Neurophysiology |date=March 2008 |volume=119 |issue=3 |pages=504–532 |doi=10.1016/j.clinph.2007.10.014}}</ref>
=== Treatment ===
{{expand section|date=January 2024}}
Repetitive high frequency TMS (rTMS) has been investigated as a possible treatment option with various degrees of success in conditions including<ref name=Chen2008/><ref>{{Cite journal |last=Lefaucheur |first=Jean-Pascal |last2=André-Obadia |first2=Nathalie |last3=Antal |first3=Andrea |last4=Ayache |first4=Samar S. |last5=Baeken |first5=Chris |last6=Benninger |first6=David H. |last7=Cantello |first7=Roberto M. |last8=Cincotta |first8=Massimo |last9=de Carvalho |first9=Mamede |last10=De Ridder |first10=Dirk |last11=Devanne |first11=Hervé |last12=Di Lazzaro |first12=Vincenzo |last13=Filipović |first13=Saša R. |last14=Hummel |first14=Friedhelm C. |last15=Jääskeläinen |first15=Satu K. |date=November 2014 |title=Evidence-based guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS) |url=https://doi.org/10.1016/j.clinph.2014.05.021 |journal=Clinical Neurophysiology |volume=125 |issue=11 |pages=2150–2206 |doi=10.1016/j.clinph.2014.05.021 |issn=1388-2457}}</ref>
*Chronic [[neuropathic pain]]
*Motor diseases (e.g., [[Parkinson's disease]], [[essential tremor]])
*[[Amyotrophic lateral sclerosis]]
*[[Multiple sclerosis]]
*[[Epilepsy]]
*Disorders of consciousness (e.g., [[vegetative state]] or [[minimally conscious state]])
*[[Alzheimer's disease|Alzheimer’s disease]]
*Psychiatric diseases, such as [[Depression (mood)|depression]],<ref>{{Cite journal |last=Hernández-Sauret |first=Ana |last2=Martin de la Torre |first2=Ona |last3=Redolar-Ripoll |first3=Diego |date=2024-05-21 |title=Use of transcranial magnetic stimulation (TMS) for studying cognitive control in depressed patients: A systematic review |url=https://doi.org/10.3758/s13415-024-01193-w |journal=Cognitive, Affective, & Behavioral Neuroscience |language=en |doi=10.3758/s13415-024-01193-w |issn=1531-135X|doi-access=free }}</ref> [[Obsessive–compulsive disorder|obsessive compulsive disorder]], [[schizophrenia]], [[Anxiety disorder|anxiety]] and [[Tourette syndrome]]
== Adverse effects ==
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The induced electric field inside the brain tissue causes a change in transmembrane potentials resulting in depolarization or hyperpolarization of neurons, causing them to be more or less excitable, respectively.<ref name=Walsh />
TMS usually stimulates to a depth from 2 to 4 cm below the surface, depending on the coil and intensity used. Consequently, only superficial brain areas can be affected.<ref>{{Cite journal |last=Lefaucheur |first=Jean-Pascal |last2=André-Obadia |first2=Nathalie |last3=Antal |first3=Andrea |last4=Ayache |first4=Samar S. |last5=Baeken |first5=Chris |last6=Benninger |first6=David H. |last7=Cantello |first7=Roberto M. |last8=Cincotta |first8=Massimo |last9=de Carvalho |first9=Mamede |last10=De Ridder |first10=Dirk |last11=Devanne |first11=Hervé |last12=Di Lazzaro |first12=Vincenzo |last13=Filipović |first13=Saša R. |last14=Hummel |first14=Friedhelm C. |last15=Jääskeläinen |first15=Satu K. |date=November 2014 |title=Evidence-based guidelines on the therapeutic use of repetitive transcranial magnetic stimulation (rTMS) |url=https://linkinghub.elsevier.com/retrieve/pii/S138824571400296X |journal=Clinical Neurophysiology |language=en |volume=125 |issue=11 |pages=2150–2206 |doi=10.1016/j.clinph.2014.05.021}}</ref> Deep TMS can reach up to 6 cm into the brain to stimulate deeper layers of the [[motor cortex]], such as that which controls leg motion. The path of this current can be difficult to model because the brain is irregularly shaped with variable internal density and water content, leading to a nonuniform magnetic field strength and [[Electrical conduction|conduction]] throughout its tissues.<ref>See:
# {{cite journal | vauthors = Zangen A, Roth Y, Voller B, Hallett M | title = Transcranial magnetic stimulation of deep brain regions: evidence for efficacy of the H-coil | journal = Clinical Neurophysiology | volume = 116 | issue = 4 | pages = 775–779 | date = April 2005 | pmid = 15792886 | doi = 10.1016/j.clinph.2004.11.008 | s2cid = 25101101 }}
# {{cite journal | vauthors = Huang YZ, Sommer M, Thickbroom G, Hamada M, Pascual-Leonne A, Paulus W, Classen J, Peterchev AV, Zangen A, Ugawa Y | display-authors = 6 | title = Consensus: New methodologies for brain stimulation | journal = Brain Stimulation | volume = 2 | issue = 1 | pages = 2–13 | date = January 2009 | pmid = 20633398 | pmc = 5507351 | doi = 10.1016/j.brs.2008.09.007 }}</ref>
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The effects of TMS can be divided based on frequency, duration and intensity (amplitude) of stimulation:<ref>{{cite journal | vauthors = Rubens MT, Zanto TP | title = Parameterization of transcranial magnetic stimulation | journal = Journal of Neurophysiology | volume = 107 | issue = 5 | pages = 1257–1259 | date = March 2012 | pmid = 22072509 | pmc = 3311692 | doi = 10.1152/jn.00716.2011 }}</ref>
* Single or paired pulse TMS causes neurons in the neocortex under the site of stimulation to [[Depolarization|depolarize]] and discharge an [[action potential]]. If used in the [[primary motor cortex]], it produces muscle activity referred to as a [[Evoked potential#Motor evoked potentials|motor evoked potential]] (MEP) which can be recorded on [[electromyography]]. If used on the [[occipital cortex]], '[[phosphene]]s' (flashes of light) might be perceived by the subject. In most other areas of the cortex, there is no conscious effect, but behaviour may be altered (e.g., slower reaction time on a cognitive task), or changes in brain activity may be detected using diagnostic equipment.<ref name="Handbook of Transcranial Magnetic Stimulation">{{cite book | author-link1 = Alvaro Pascual-Leone | vauthors = Pascual-Leone A, Davey N, Rothwell J, Wassermann EM, Puri BK | year = 2002 | title = Handbook of Transcranial Magnetic Stimulation | publisher = Edward Arnold|location=London | isbn = 978-0-340-72009-7 }}</ref>
* Repetitive TMS produces longer-lasting effects which persist past the period of stimulation. rTMS can increase or decrease the excitability of the [[corticospinal tract]] depending on the intensity of stimulation, coil orientation, and frequency. Low frequency rTMS with a stimulus frequency less than 1 Hz is believed to inhibit cortical firing while a stimulus frequency greater than 1 Hz, or high frequency, is believed to provoke it.<ref name="ReferenceA">{{cite journal | vauthors = Cusin C, Dougherty DD | title = Somatic therapies for treatment-resistant depression: ECT, TMS, VNS, DBS | journal = Biology of Mood & Anxiety Disorders | volume = 2 | issue = 1 | pages = 14 | date = August 2012 | pmid = 22901565 | pmc = 3514332 | doi = 10.1186/2045-5380-2-14 | doi-access = free }}</ref> Though its mechanism is not clear, it has been suggested as being due to a change in synaptic efficacy related to [[long-term potentiation]] (LTP) and long-term depression like plasticity (LTD-like plasticity).<ref name=Fitzgerald>{{cite journal | vauthors = Fitzgerald PB, Fountain S, Daskalakis ZJ | title = A comprehensive review of the effects of rTMS on motor cortical excitability and inhibition | journal = Clinical Neurophysiology | volume = 117 | issue = 12 | pages = 2584–2596 | date = December 2006 | pmid = 16890483 | doi = 10.1016/j.clinph.2006.06.712 | s2cid = 31458874 }}
=== Coil types ===
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=== Study blinding ===
Mimicking the physical discomfort of TMS with [[placebo]] to discern its true effect is a challenging issue in research.<ref name=Lefaucher1 /><ref name=Rossi /><ref name=Duecker>{{cite journal | vauthors = Duecker F, Sack AT | title = Rethinking the role of sham TMS | journal = Frontiers in Psychology | volume = 6 | page= 210 | year = 2015 | pmid = 25767458 | pmc = 4341423 | doi = 10.3389/fpsyg.2015.00210 | doi-access = free }}</ref><ref name = Davis>{{cite journal | vauthors = Davis NJ, Gold E, Pascual-Leone A, Bracewell RM | title = Challenges of proper placebo control for non-invasive brain stimulation in clinical and experimental applications | journal = The European Journal of Neuroscience | volume = 38 | issue = 7 | pages = 2973–2977 | date = October 2013 | pmid = 23869660 | doi = 10.1111/ejn.12307 | s2cid = 2152097 | url = https://zenodo.org/record/3436292 }}</ref> It is difficult to establish a convincing [[placebo]] for TMS during [[Scientific control|controlled]] [[Clinical trial|trials]] in [[conscious]] individuals due to the neck pain, headache and twitching in the scalp or upper face associated with the intervention.<ref name=Lefaucher1 /><ref name = Rossi /> In addition, placebo manipulations can affect
A 2011 review found that most studies did not report [[unblinding]]. In the minority that did, participants in real and sham rTMS groups were not significantly different in their ability to correctly guess their therapy, though there was a trend for participants in the real group to more often guess correctly.<ref>{{cite journal | vauthors = Broadbent HJ, van den Eynde F, Guillaume S, Hanif EL, Stahl D, David AS, Campbell IC, Schmidt U | display-authors = 6 | title = Blinding success of rTMS applied to the dorsolateral prefrontal cortex in randomised sham-controlled trials: a systematic review | journal = The World Journal of Biological Psychiatry | volume = 12 | issue = 4 | pages = 240–248 | date = June 2011 | pmid = 21426265 | doi = 10.3109/15622975.2010.541281 | s2cid = 21439740 }}</ref>
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===Depression===
The National Institutes of Health estimates depression medications work for 60 percent to 70 percent of people who take them.<ref>{{cite book | url=https://www.ncbi.nlm.nih.gov/books/NBK20369/|title= Information about Mental Illness and the Brain|year= 2007|publisher= National Institutes of Health (US)}}</ref><ref>
=== Obsessive–compulsive disorder (OCD) ===
In August 2018, the US Food and Drug Administration (US FDA) authorized the use of TMS developed by the [[Israel]]i company [[Brainsway]] in the treatment of [[obsessive–compulsive disorder]] (OCD).<ref>{{cite web |date=2020-02-20 |title=FDA permits marketing of transcranial magnetic stimulation for treatment of obsessive compulsive disorder |url=https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm617244.htm |website=[[Food and Drug Administration]]}}</ref>
In 2020, US FDA authorized the use of TMS developed by the U.S. company MagVenture Inc. in the treatment of OCD.<ref>{{Cite web |title=MagVenture receives FDA clearance for OCD {{!}} Clinical TMS Society |url=https://www.clinicaltmssociety.org/news/2020-08/magventure-receives-fda-clearance-ocd-0 |access-date=2023-10-11 |website=www.clinicaltmssociety.org}}</ref>
In 2023, US FDA authorized the use of TMS developed by the U.S. company Neuronetics Inc. in the treatment of OCD.<ref>{{Cite web |title=FDA clears OCD motor threshold cap for transcranial magnetic stimulation system |url=https://www.healio.com/news/neurology/20230613/fda-clears-ocd-motor-threshold-cap-for-transcranial-magnetic-stimulation-system |access-date=2023-10-11 |website=www.healio.com |language=en}}</ref>
====Other neurological areas====
In the [[European Economic Area]], various versions of
[[Alzheimer's disease]],<ref name=OCD/>
[[autism]],<ref name=OCD/>
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* In August 2012, the jurisdiction covering Arkansas, Louisiana, Mississippi, Colorado, Texas, Oklahoma, and New Mexico determined that there was insufficient evidence to cover the treatment,<ref>{{cite web |author=Novitas Solutions, Inc. |date=2013-12-04 |title=LCD L32752 – Transcranial Magnetic Stimulation for Depression |url=https://hwscenter.com/treatments/#neuropsychology |access-date=2014-02-17 |work=Contractor's Determination Number L32752 |publisher=[[Centers for Medicare and Medicaid Services]]}}</ref> but the same jurisdiction subsequently determined that Medicare would cover TMS for the treatment of depression after December 2013.<ref>{{cite web|url=http://www.cms.gov/medicare-coverage-database/details/lcd-details.aspx?LCDId=33660&ContrId=259&bc=IAAAAAgAAAAAAA%3d%3d&|title=LCD L33660 – Transcranial Magnetic Stimulation (TMS) for the Treatment of Depression|author=Novitas Solutions, Inc.|work=Contractor's Determination Number L33660|publisher= [[Centers for Medicare and Medicaid Services]]|date=2013-12-05|access-date=2014-02-17}}</ref>
* Subsequently,{{when|date=April 2021}} some other Medicare jurisdictions added Medicare coverage for depression.{{citation needed|date=April 2021}}<!-- By mid-2020, it was available in Illinois, to this editor. Acwilson9 -->
== Limitations ==
There are serious concerns about stimulating brain tissue using non-invasive magnetic field methods:
First, the uncertainty in the dose (time and technical field parameters) for correct and healthy stimulation is a complex and challenging issue.<ref>Benussi A, Pascual-Leone A, Borroni B (2020). "Non-Invasive Cerebellar Stimulation in Neurodegenerative Ataxia: A Literature Review". ''International Journal of Molecular Sciences.'' 21 (6): 1948. doi:10.3390/ijms21061948</ref> While neurophysiology lacks knowledge about the nature of such a treatment of nervous diseases at the cellular level,<ref>Rosa, MA; Lisanby, SH (2012). "Somatic treatments for mood disorders". ''Neuropsychopharmacology.'' 37 (1): 102–116. doi:10.1038/npp.2011.225</ref> this method involves excessive exposure of the brain to an intense field, which is several times and even orders of magnitude higher than natural electromagnetic fields in the brain.<ref>Grimaldi G, Argyropoulos GP, Boehringer A, Celnik P, Edwards MJ, Ferrucci R, et al. (2014). "Non-invasive cerebellar stimulation--a consensus paper" (PDF). ''Cerebellum.'' 13 (1): 121–138. doi:10.1007/s12311-013-0514-7</ref><ref>Siebner HR, Hartwigsen G, Kassuba T, Rothwell JC (2009). "How does transcranial magnetic stimulation modify neuronal activity in the brain? Implications for studies of cognition". ''Cortex; A Journal Devoted to the Study of the Nervous System and Behavior.'' 45 (9): 1035–1042. doi:10.1016/j.cortex.2009.02.007</ref>
Second, it is impossible to localize the effect of stimulation on specific neural networks that need to be treated.<ref name="Sparing and Mottaghy_2008">Sparing R, Mottaghy FM (2008). "Noninvasive brain stimulation with transcranial magnetic or direct current stimulation (TMS/tDCS)-From insights into human memory to therapy of its dysfunction". ''Methods.'' 44 (4): 329–337. doi:10.1016/j.ymeth.2007.02.001</ref>
Neuronal activity related to mental processes, neuronal correlates of cognitive functions are still intriguing questions for contemporary research. Non-invasive brain tissue stimulation targets a large area of poorly characterized tissue. An undefined dose and target of radiation can destroy healthy cells during a treatment procedure. Because it is unclear whether magnetic fields reach only those neural structures of the brain that need treatment, this uncertainty challenges the selection of treatment for neurological disorders by magnetic fields. Thus, magnetic field exposure may destroy healthy neuronal structures. The inability to localize the effect of stimulation makes it challenging to target stimulation only to the desired neural networks. <ref name="Sparing and Mottaghy_2008" />
== See also ==
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