Talk:Transcranial magnetic stimulation

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Contents

[edit] Consumer TMS IS Available

There is an extremely affordable TMS device ("Shakti") available from www.shaktitechnology.com that I recently ran across and ordered for my own experiments. The 4-coil device was only about $100. 2-coil versions are around $60-70 and 8 coil devices are around $200-250. It came with software (since replaced by a much more effective version), and took some time to figure out, but it seems to be producing some interesting results. The device was developed by Todd Murphy, a Behavioral Neuroscientist associated with Dr. Michael Persinger of Laurentian University in Canada. It was created for the purpose of exploring the "spiritual aspects" of neuroscience. It allows one to apply signals derived from the Amygdala, Hippocamus, and other limbic-system modules of the brain, which can then be applied to a number of areas of the cortex, such as the temporals, parietals, pre-frontal, etc. My first experience was from applying an Amygdaloid signal to the left temporals. I noticed afterward a fairly pronounced feeling of well-being. I then applied the same signal to both the left and right pre-frontal cortex, followed by a Hippocampal signal to the same region. I actually exceeded the recommended session parameters but following this approach, but did not wish to wait the suggested 72 hours between sessions. The most interesting thing that I noticed after the sessions was that, in addition to feeling quite upbeat, I started to immediately try to complete tasks I had been putting off for weeks. I almost felt obsessive about doing these tasks. I also noticed that I had an unending stream of ideas flowing through my head which continued for several days straight. It was like a miniature personal renaissance. I will wait until the 72 hours is up before trying any more experiments, but I think this is quite promising.

NOTE: Shakti is NOT TMS. Shakti uses different principles and magnetic fields much fainter than the ones used in TMS. TMS uses simple signals (Pulses) while Shakti uses "complex" magnetic signals.


—Preceding unsigned comment added by 66.26.245.206 (talk) 11:22, 24 November 2007 (UTC)

[edit] Outside Opinion

I am a patient who has been receiving rTMS treatments for severe depression since 1998. It's been my salvation - the only treatment that has worked for me. If you have any questions from a patient's point of view, my email is joan.miller AT comcast.net.

[edit] Question

Does anyone know the resolution of this technique (i.e. how small an area of the brain may be targeted)? Eldereft 05:28, 3 November 2005 (UTC)

The interesting thing is that literature on this subject measures the affected brain in cm^2. Typical value is approximately 1-2cm^2. I don't know how deep it goes, but I'm guessing around 1cm. So around 2cm^3 of affected volume in the 90% power zone. The technique will never be able to target more locally than this, since there is no such thing as a magnetic monopole. The technique will never be able to locally target an area inside the brain. The closer to the surface of the scalp the focus of the magnetic field is, the higher the resolution can be. If you want to target the center of the brain, you will not be able to do so without also targeting the rest of the brain. Personally, I think this technique will never develop beyong a curiousity, and perhaps zapping people who already have a problem, where "it can't get any worse... so zap away" will take over (as it did for electroshock). —Preceding unsigned comment added by 82.75.128.73 (talk) 14:14, 17 February 2008 (UTC)

[edit] Re-edit Please!

The flow of the page is confusing and it is also accumulating too much references to single studies added by self-publicists (no names) which have not been replicated. ==

  • I plan to reorganise the page into a section on history, how it works (the actual process in the clinic), proposed theories, controversy, and references to similar techniques DontCallMeShirley 15:12, 11 January 2006 (EST)

[edit] Homemade Devices

A while back I stumbled into some sites about homemade TMS devices, I remeber they were basicly a wood rod with magnets on its tips and conected to some sort of bearings in the middle, most were hand cranked. But I seem to be unable to find the said sites, nor any other with instructions on this, does any one knows where I can find something in those lines? TiagoTiago 21:24, 2 June 2006 (UTC)

Forget it. You are talking about a device costing 10s of thousands of dollars. The magnetic field strength needed to have any effect on the cortex requires 1000s of amps - not something involving 'a wood rod with magnets on its tips'. Sorry.
This is a sham, and would be something like going to a do-it-yourself ECT operator. Though it is more or less a noninvasive procedure, it is certianly not something people want to be fooling around with items "built" from componenents ordered from the Web or the back of a magazine. And as FDA approval becomes more and more imminent -- Neuronetics' TMS device may receive FDA approval by the end of October '06 -- and it becomes more of an acknowledged mode of treatment, regulations will come into place. --Markt3 05:41, 26 September 2006 (UTC)

[edit] Consumer availability

Are there any rTMS devices on the market for purchase by consumers? (if so, at what prices?) Anarchist42 23:28, 19 January 2006 (UTC)

No. TMS is a medical device and can only be used by a qualified physician.

  • This is flase. You do not need to be a physician to use a TMS device; they are allowed in research settings by trained users as well. Often you are required to have CPR certification as well, however. Semiconscious • talk 17:47, 24 January 2006 (UTC)
In other words it is not really available as a treatment for depression (a shame, it would be easier than pouring cold water into my ear). Anarchist42 19:41, 24 January 2006 (UTC)
  • Well, no quite true either. Using TMS to treat depression is valid in theory, and there is some good evidence supporting this, but it's still in the experimental phase right now. You could always volunteer for a research study at a local university or something if they're conducting anything. However expect to wait a while before you can go into any doctor's office and get TMS for depression. Semiconscious • talk 21:21, 24 January 2006 (UTC)
Actually there are a small but growing number of sites that offer TMS in a clinical outpatient settings. It is done as an off-label procedure, which means that insurance will not cover it, and it tends to be pricey (e.g. $250 - 350 per session for a two or three-week induction period. It it proves successful in a given patient, an ongoing maintenance regimen would be worked out (similarly to ECT), with patients receiving regular treatments on an indefinitely basis. Pricey, but cheaper than ECT, in that patient does not need to be admitted, no ansthesia is required, etc.--Markt3 05:36, 26 September 2006 (UTC)
I've read the studies, and it seem clear to me that TMS should indeed be a very effective (and non-pharmaceutical) treatment option. Since TMS puts no money into the coffers of pharmaceutical corporations, I doubt it will ever be approved. Anarchist42 21:39, 24 January 2006 (UTC)
  • It's not as simple as you may think. Just because it seems clear to you doesn't mean it is an approved treatment option. People still don't know what TMS does to the brain over prolonged usage. The neural effects are being researched right now. People also don't know what's going on in the brain to alleviate symptoms of depression. A lot of research is being done on this. Making the assumption that the pharmaceutical industry is somehow supressing the treatment is rather broad; there are a lot of people working on this field of research right now, and a lot of people stand to make money off of it. The FDA needs to be shown that it is more safe and effective over other treatments that carry less risk (i.e., seizure). Semiconscious • talk 21:57, 24 January 2006 (UTC)
I'd had enough experience with (sometimes bogus) "approved treatment options", as well as (sometimes effective) "non-approved treatment options" to be less interested in "official approval" than in actual efficacy. Anarchist42 22:52, 24 January 2006 (UTC)
I'm sorry to hear that. Unfortunately we as individuals can't judge efficacy right now. Semiconscious • talk 23:10, 24 January 2006 (UTC)
Perhaps many individuals can't, but I'm quite capable of understanding research studies and filtering out bias and statistical flaws - my experience with psychiatrists is that they tend not to be so capable. Anarchist42 23:59, 24 January 2006 (UTC)

There is a new product that is in for FDA appoval please see link. http://www.neuralieve.com/

[edit] Anonymous Comment

Since the TMS is essentialy inducing electrical signals in the brain through the use of powerful magnetic fields, could it theoretically restart the brain of a patient who has died and is now otherwise in good condition?

Like say a heart attack. Could they keep the patient on ice and a machine that keeps the blood flowing and oxygenated and then use TMS to restart the brain? - June 9th 2006

[edit] transcranial direct current stimulation

New Scientist Article

[edit] TMS as an interrogation/control

enhancing geek brains is one thing, directly controlling human value judgements to gain a military/police advantage is quite another: Scientific American article on the first success in magnetic mind control

[edit] Massimini reference

I removed this at the end of TMS in Research section (add back if you can add the suitable connection to TMS):

Massimini et al. (Science, 2005)(Massimini M, Ferrarelli F, Huber R, Esser SK, Singh H, Tononi G. Breakdown of cortical effective connectivity during sleep. Science. 2005 Sep 30;309(5744):2228-32.) used EEG to show that during sleep, brain areas do not pass signals to other brain areas as effectively as during wakefulness.

[edit] References from Brain-computer interface page

I had archieved the references below from the Brain-computer interface page as they were off topic. Reviewing them now, they mostly seem to relate to magnetic stimluation of the brain and are published in scholarly journals so I'm posting them here in case they help. Cheers--Saganaki- 03:08, 12 October 2006 (UTC)

  • Arber, S.L., J.C. Lin, Microwave Effects on Helix Asperse Neurons, Fourth Ann. Mtg. Bioelectromagnetics Soc., Los Angeles, CA, June 1982.
  • Arber, S.L. and J.C. Lin, Role of External Calcium in Microwave-Induced Snail Neuron Response, Fifth Ann. Scientific Session Bioelectromagnetic Soc., Boulder, CO, June 1983.
  • Caldwell, L.R., J.C. Lin and A.W. Guy, Behavioral Changes of Rats Exposed to Microwave Radiation, IEEE S-MTT International Symp., Atlanta, GA, June 1974.
  • Dalecki,D., Child, S.Z., Raemanand, C.H. and Carlstensen, E.: Tactile perception of ultrasound, Journal of acoustical society of America, pp3165-3170,1995.
  • J.Edrich and T.Zhang: Ultrasonically Focused Neuromagnetic Stimulation, Proceeding of the Annual Conference on Engineering in Medicine and Biology, v15. pt3, pp.1253-1254,1993.
  • Fetz E.E., Baker M.A. (1973) Operantly conditioned patterns on precentral unit activity and correlated responses in adjacent cells and contralateral muscles. J Neurophysiol. Mar;36(2):179-204.
  • Gavrilov, L.R., Tsirulnikov, E.M., and Davies, I.：Application of Focused Ultrasound for The Stimulation of Neural Structures, Ultrasound in Medicine & Biology,Vol.22,No2, pp.179-192,1996
  • Ginsburg, K., J.C. Lin and W.D. O'Neill, Microwave Effects on Spiking Statistics of Single Neurons, BEMS Ninth Annual Meeting Program, Portland, Oregon, June 1987.
  • Ginsberg, K.S., J.C. Lin, S. Murphy, and M.F. Lin, Microwave Effect On Input Resistance And Action Potential Firing Of Snail Neurons, IEEE Trans. Biomed. Eng., Vol. 39, pp. 1011-1021, 1992.
  • Guy, A.W. and J.C. Lin and F.A. Harris, The Effect of Microwave Radiation on Evoked Tactile and Auditory CNS Responses in Cats, International Microwave Symp., Ottawa, Canada, May 1972.
  • Guy, A.W., E.M. Taylor, B. Ashleman and J.C. Lin, Microwave Interaction with the Auditory Systems of Humans and Cats, IEEE G-MTT Int. Microwave Symp., Univ. of Colo., Boulder, CO, June 1973.
  • Guy, A.W., C.K. Chou, J.C. Lin and D. Christensen, Microwave Induced Acoustic Effects in Mammalian Auditory Systems and Physical Materials, N.Y. Acad. Sci. Conf. Biol. Effects of Nonionizing Radiation, New York, Feb. 1974.
  • Lin, J.C. and J. Salinger, Microwave Measurement of Respiration, IEEE S-MTT International Microwave Symp., Palo Alto, CA, May 1975.
  • Lin, J.C. and C.K. Lam, A Theoretical Study of Microwave Generated Auditory Phenomena in Mammalian Cranial Structures, USNC/URSI - Biological Effects Series, Boulder, CO, Oct. 1975.
  • Lin, J.C., Predicted Frequency and Threshold of Microwave-Induced Auditory Sensation, USNC/URSI - Biological Effects Series, Amherst, MA, Oct. 1976.
  • Lin, J.C., E. Dawe and J. Majcherek, A Noninvasive Microwave Apnea Detector, San Diego Biomedical Symp., San Diego, CA, Feb 1977.
  • Lin, J.C., R.J. Meltzer and F.K. Redding, Microwave Evoked Potentials in Cats, San Diego Biomedical Symposium, San Diego, CA, Feb. 1978.
  • Lin, J.C., R.J. Meltzer and F.K. Redding, Characteristics of Microwave Auditory Effects: Theory and Experiments, URSI Open Symp. on Biological Effects of Electromagnetic Waves, Helsinki, Finland, August 1978.
  • Lin, J.C., S.L. Arber, Response of Snail Nerve Cells to Noise Modulated Microwave Field, Fourth Ann. Mtg. Bioelectromagnetic Soc., Los Angeles, CA, 1982.
  • Lin, J.C. and Charles C. Thomas, Microwave Auditory Effects And Applications, Publisher, Springfield, IL 1978, 221 pp.
  • Lin, J.C., Electromagnetic Interaction with Nervous System Structure and Function, IEEE Engg. in Biology Conf., Chicago, IL, September 1985.
  • Lin, J.C., J.L. Su and Y. Wang, Measurement of Microwave-Induced Thermoelastic Pressure Wave Propagation in Cat Brains, Ann. Meeting of the Bioelectromagnetic Society, Madison, WI June 1986.
  • Lin, J.C. W.D. O'Neill, A. Field and K. Ginsburg, Pulsed High Power Microwave Effects on Spontaneous Firing Activities of Snail Neurons, BEMS Ninth Annual Meeting, Portland, Oregon, June 1987.
  • Ma, Y.C., J.C. Lin, W.D. O'Neill and S. Arber, Real Time Processing of Neuronal Response to Microwave, IEEE Engg. Medicine Biol. Conf., Los Angeles, CA, September 1984.
  • R.T.Mihran, F.S.Barnes, H.Wachtel: Temporally-Specific Modification of Myelinated Axon Excitability in vitro Following A Single Ultrasound Pulse, Ultrasound in Medicine & Biology, Vol.16, No.3, pp.297-309, 1990
  • Nefcy, P.M. and J.C. Lin, A Model for Auditory Evoked Potentials, Annual Conf. on Engg. in Medicine and Biology, Atlanta, Georgia, Oct. 1978.
  • Neilly, J.P., V. Kriho, S.L. Arber and J.C. Lin, Ultrastructural Studies of Microwave Irradiated Snail Nerve Cells, Fifth Ann. Scientific Session Bioelectromagnetics Soc., Boulder, CO, June 1983.
  • Popovic, M.A., K.H. Chan and J.C. Lin, Microprocessor Based Non-Contact Heart Rate/Respiration Monitor, IEEE Eng. Medicine Biol. Conf., Los Angeles, CA, September 1984.
  • Taylor, E.M., A.W. Guy, B. Ashleman and J.C. Lin, Microwave Effects on Central Nervous System Attributed to Thermal Factors, IEEE G-MTT Int. Microwave Symp., Univ. of Colo., Boulder, CO, June 1973.
  • Wu, C.L. and J.C. Lin, Interaction of Modulated Electromagnetic Fields with Nervous Structures, USNC/URSI - Biological Effects Series, Boulder, CO, Oct. 1975.

[edit] Side effects

There are prominent side effects associated with ECT. Does TMS have none?--Loodog 03:56, 20 July 2007 (UTC)

As a patient of right-side 1 Hz. TMS since 1998 (for depression at Beth Israel Deaconess with Dr. Alvaro Pascual-Leone), it does give me migraines, but I know that I am an extreme case. That is not true for most patients. (I am prone to migraines.) I do feel my facial muscles twitch during treatments, but that isn't at all painful. No memory problems whatsoever. The risk of seizure has been exagerated due to researchers using the equipment inappropriately. From what I've been told, no patient has ever experienced a seizure. —Preceding unsigned comment added by 66.30.42.7 (talk) 00:04, 16 January 2008 (UTC)

As far as I know, TMS doesn't have the memory disturbance associated with ECT. However, I believe there is a risk of seizure as well as temporary language switching in bilingual people. Beyond that I'm not sure. Nathanaver 04:13, 20 July 2007 (UTC)

According to the Elata Foundation, there are not substantial side effects beyond headache and a very small risk of seizure.--Gloriamarie 23:40, 31 July 2007 (UTC)

TMS can cause facial muscles to twitch, and if the machine is used at high power this can be painful. Frontal stimulation sites (as used to treat depression) tend to be most painful. Can't find a reference immediately but I've experienced it myself. AFdeCH 21:37, 10 August 2007 (UTC)

I am rewriting the page as it is almost totally incomprehensible now with people adding every single minor trial into it. I have removed most of the trials and just given a cursory overview of the trials. I have re-ordered some of the headings and added a few more bits of technical information. This is what I have...
Give me some feedback

--Grushnik 12:42, 15 August 2007 (UTC)



Transcranial magnetic stimulation
Transcranial magnetic stimulation (TMS) is a noninvasive method to excite neurons in the brain. The excitation is caused by weak electric currents induced in the tissue by rapidly changing magnetic fields (electromagnetic induction). This way, brain activity can be triggered or modulated without the need for surgery or external electrodes. This is used to study the circuitry and connectivity of the brain.
Repetitive transcranial magnetic stimulation is known as rTMS and can produce longer lasting changes. Numerous small-scale pilot studies have studies have shown it could be a treatment tool for various neurological conditions (e.g. migraine, stroke, dystonia), but as yet no large scale trial has been done, the therapeutic potential of rTMS should not be considered proven.

Contents
1. Background
2. How TMS affects the brain
3. Technical information on TMS
4. TMS and rTMS in research
5. TMS and rTMS techniques in research
6. Risks of TMS and rTMS
7. Clinical uses of TMS and rTMS
8. TMS equipment
9. Technical information on TMS
10. References
11. See also
12. External links

Background
The principle of inductive brain stimulation with eddy currents has been noted since the 19th century. The first successful TMS study was performed by Anthony Barker et al.[2] in Sheffield, England. Its earliest application was in the demonstration of conduction of nerve impulses from the motor cortex to the spinal cord. This had been done with transcranial electrical stimulation a few years earlier, but use of this technique is limited by severe discomfort. By stimulating different points of the cortex and recording responses, e.g., from muscles, one may obtain maps of functional brain areas. By measuring EEG, information may be obtained about the healthiness of the cortex (its reaction to TMS) and about area-to-area connections.
It is also important to distinguish TMS from repetitive TMS (rTMS) as they are used in different ways for different purposes.

How TMS affects the brain
The exact details of how TMS functions are still being explored. The effects of TMS can be divided into two types depending on the mode of stimulation:
• Single or paired pulse TMS. The pulse(s) causes a population of neurons in the neocortex to depolarise and discharge an action potential. If used in the primary motor cortex, it produces a motor-evoked potential (MEP) which can be recorded on electromyography (EMG). If used on the occipital cortex, phosphenes (flashes of light) might be detected by the subject. In most other areas of the cortex, the participant does not consciously experience any effect, but his or her behaviour may be slightly altered (e.g. slower reaction time on a cognitive task), or changes in brain activity may be detected using Positron Emission Tomography or fMRI. These effects do not outlast the period of stimulation. A review of TMS can be found in the Handbook of Transcranial Magnetic Stimulation.[4]
• Repetitive TMS (rTMS) produces effects which last longer than the period of stimulation. rTMS can increase or decrease the excitability of corticospinal or corticocortical pathways depending on the intensity of stimulation, coil orientation and frequency of stimulation. The mechanisms of these effects are not clear although it is widely believed to reflect changes in synaptic efficacy akin to long-term potentiation (LTP) and long-term depression (LTD). A recent review of rTMS can be found in Fitzgerald et al, 2006.[5]

TMS and rTMS in research
Pioneers in the use of TMS in neuroscience research include Anthony Barker, Vahe Amassian, John Rothwell of the Institute of Neurology, Queen Square, London, Mark S. George, MD of the Medical University of South Carolina, David H. Avery, MD of the University of Washington at Seattle, Charles M. Epstein of Emory University, Drs. Mark Hallett, Leonardo G. Cohen, and Eric M. Wassermann of the National Institutes of Health, and Alvaro Pascual-Leone of Harvard Medical School. Currently, thousands of TMS stimulators are in use. More than 3000 scientific publications have been published describing scientific, diagnostic, and therapeutic trials.

TMS and rTMS techniques in research
One reason TMS is important in neuroscience is that it can demonstrate causality. A noninvasive mapping technique such as fMRI allows researchers to see what regions of the brain are activated when a subject performs a certain task, but this is not proof that those regions are actually used for the task; it merely shows that a region is associated with a task. If activity in the associated region is suppressed (‘knocked out’ or ‘lesioned’) with TMS stimulation and a subject then performs worse on a task, this is much stronger evidence that the region is used in performing the task.
For example: subjects asked to memorize and repeat a stream of numbers would likely show, via fMRI, activation in the prefrontal cortex (PFC), which seems to be important in short-term memory. If the researcher then interfered with the PFC via TMS, the subjects' ability to remember numbers would decline, and the researcher would have evidence that the PFC is important for short-term memory, because reducing subjects' PFC capability led to reduced short-term memory.
 This ‘knock-out’ technique can be done in two ways:
 1. Online TMS: where subjects perform the task and at a specific timepoint (usually in the order of 1-200ms) of the task, a TMS pulse is given to a particular part of the brain. This should affect the performance of the task specifically, and thus demonstrate that this task involves this part of the brain at this particular time point. The advantage of this technique is that any positive result can provide a lot of information about how and when the brain processes a task, and there is no time for a placebo effect or other brain areas to compensate. The disadvantages of this technique is that one has to know roughly when the part of the brain is responsible for the task so lack of effect is not conclusive.
2. Offline repetitive TMS: where performance at a task is measured initially and then repetitive TMS is given over a few minutes, and the performance is measured again. This technique has the advantage of not requiring knowledge of the timescale of how the brain processes. However repetitive TMS is very susceptible to the placebo effect. Additionally, the effects of repetitive TMS are variable between subjects and also for the same subject.
A variant of this technique is the ‘enhancement’ technique, where repetitive TMS is delivered to enhance performance. This is even harder to achieve than the ‘knock-out’ technique.

Risks of TMS and rTMS
As it induces an electrical current in the human brain, TMS and rTMS can produce a seizure. The risk is very low with TMS except in patients with epilepsy and patients on medications. The risk is significantly higher in rTMS especially when given at rates >5Hz at high intensity.
The only other effects of TMS which are reported in most subjects are:
• discomfort/ pain from the stimulation of the scalp and associated nerves on the overlying skin
• hearing from the loud click made by the TMS pulse

Clinical uses of TMS and rTMS
The uses of TMS and rTMS can be divided into:
• Diagnostic
• Therapeutic

TMS for diagnosis
TMS is used currently clinically to measure activity and function of specific brain circuits in humans. The most robust and widely-accepted use is in measuring the connection between the primary motor cortex and a muscle (i.e. MEP amplitude, MEP latency, central motor conduction time). This is most useful in stroke, spinal cord injury, multiple sclerosis and motor neuron disease. There are numerous other measures which have been shown to be abnormal in various diseases but few are validated or reproduced and more importantly, no one knows the significance of it. The most famous is short-interval intracortical inhibition (SICI) which measures the internal circuitry (intracortical circuits) of the motor cortex (Kujirai et al., 1993).
Plasticity of the human brain can also be measured now with repetitive TMS (and variants of the technique, e.g. theta-burst stimulation, paired associative stimulation) and it has been suggested that this is the primary abnormality in a number of conditions.

TMS for therapy
It is important to stress that there is no strong evidence for the use of TMS for therapy of any condition. A large number of studies with TMS and repetitive TMS has been conducted for a variety of neurological and psychiatric conditions but few have been confirmed and most show very modest effects if any. Some conditions which have been reported (but not proven) to be responsive to TMS-based therapy are:
• Stroke
• Tinnitus
• Parkinson’s Disease
• Dystonia
• Epilepsy
• Migraine
• Dysphasia
• Neglect
• Chronic pain
• Depression
It is important to stress that in a vast majority of these studies, no adequate control of placebo effect was possible and thus it is tempting to wonder if this effect is placebo.

Technical information on TMS
TMS is simply the application of the principle of induction to get electrical current across the insulating tissues of the scalp and skull without discomfort. A coil of wire, encased in plastic, is held to the head. When the coil is energized by the rapid discharge of a large capacitor, a rapidly changing current flows in its windings. This produces a magnetic field oriented orthogonally to the plane of the coil. The magnetic field passes unimpeded through the skin and skull, inducing an oppositely directed current in the brain that flows tangentially with respect to skull. The current induced in the structure of the brain activates nearby nerve cells in much the same way as currents applied directly to the cortical surface. The path of this current is complex to model because the brain is a non-uniform conductor with an irregular shape. With stereotactic, MRI-based control the precision of targeting TMS can be approximated to a few millimeters (Hannula et al., Human Brain Mapping 2005).

Typical data:
Magnetic field: often about 2 tesla on the coil surface and 0.5 T in the cortex
Current rise time: zero to peak, often around 70-100 microseconds
Waveform: monophasic or biphasic

TMS equipment
The major manufacturers for general purpose TMS and repetitive TMS equipment are:
• The Magstim Company, UK
• Medtronics, USA
• Cadwell, USA
• Dantec, Denmark
• Schwarzer, Germany
Several TMS/rTMS devices are approved by the US Food and Drug Administration (FDA) for stimulation of peripheral nerve and, therefore, can be used "off label" by individual physicians to treat brain disorders, essentially in any way they believe appropriate, analogous to the off label use of medications. However, most legitimate use of TMS in the US and elsewhere is currently being done under research protocols approved by hospital ethics boards and, in the US, often under Investigational Device Exemption from the FDA. The requirement for FDA approval for research use of TMS is determined by the degree of risk as assessed by the investigators, the FDA, and the local ethics authority. An application for clearance of TMS Therapy as a treatment for depression was submitted to the FDA in 2006. The FDA convened its Neurological Devices Panel on January 26, 2007 to review the TMS Therapy application. The results of this panel meeting were mixed with no concerns regarding the safety of this treatment, however, there was clear questioning of the efficacy of this treatment [7]. A final decision from the FDA in regard to approving TMS as a treatment for depression is expected in the first half of 2007. As regulated medical devices, TMS devices are not sold to the general public. They are also expensive (US$25,000-100,000; together with state-of-the-art targeting and recording instruments, up to about US$500,000). In Europe, TMS devices that have been manufactured according to the Medical Device Directive have been granted the CE mark and can thus be freely marketed within the EU.

References
[1] Ebmeier and Hermann (December 2006). "Factors Modifying the Efficacy of Transcranial Magnetic Stimulation in the Treatment of Depression: A Review". Journal of CLinical Psychiatry.
[2] Barker AT, Jalinous R, Freeston IL. (1985). "Non-invasive magnetic stimulation of human motor cortex.". Lancet 1: 1106-1107.
[3] (May 22, 2007) "NeuroStar(R) TMS Therapy Improved Quality Of Life In Patients With Major Depression In Clinical Trials".
[4] Pascual-Leone A, Davey N, Rothwell JC, Wassermann EM, Puri BK (2002). Handbook of Transcranial Magnetic Stimulation.
[5] Fitzgerald PB, Fountain S, Daskalakis ZJ (2006). "A comprehensive review of the effects of rTMS on motor cortical excitability and inhibition". Clinical Neurophysiology.
[6] "TMS terminology", BioMag Laboratory at Helsinki University Central Hospital
[7] Bridges, Andrew (January 2007). "Panel questions magnet therapy results".

See also
• Cranial Electrotherapy Stimulation (CES)
• Transcranial direct current stimulation (tDCS)
• Electroconvulsive therapy (ECT)

External links
• CIMIT - Center For Integration Of Medicine And Innovative Technology
• Recording of EEG response due to TMS
• Transcranial magnetic stimulation in psychiatry
• BioMag Laboratory, Helsinki
• OpenStim: The Open Noninvasive Brain Stimulator
• MagVenture: Magnetic Stimulation - Principles
• Magnets may make the brain grow stronger
• Elata Foundation non-profit for TMS development and education

[edit] Different View Point

From what I have read on this subject, which is admittedly very little, all those experimenting with this theory are from the medical background. Is there any research that include Electrodynamicists or at least Electrical Engineers or Physicists with a background in electromagnetics? I have yet to see any reference to either near field strength, frenel zones, or Fraunhofer region power densities. To be very honest, it seems that medical industry is once again not practicing the scientific method and only testing outcome without defining variables. If anyone has any reference to in-depth electromagnetic modeling (yes it can be done with programs like HFSS, FEKO, or WIPL-D depending on what method you prefer on very customized clusters or high end computers), it would be very interesting to read. If one could understand the entire body as a system, and its associated subsystems in a meaningful way by defining it within the boundaries (used loosely here) of electromagnetics, then they would open a whole line in treatments and would most likely have less side affects than current pharmaceuticals solutions. Again, any references to well defined research from the electrodynamics view point would be very helpful. —Preceding unsigned comment added by Cwru53 (talk • contribs) 02:26, 11 November 2007 (UTC)

[edit] TMS research is multi-disciplinary

Of course, physicists and engineers are involved in TMS research. In my lab, medics collaborate with engineers, neuroscientists, psychologists, medical physicists and mathematicians. Modelling papers on TMS fields are published in engineering and medical journals (just look up Pubmed), and the companies building these devices are engineers too trying to improve their product line.

[edit] Why is rTMS knockout research suseptible to the placebo effect?

The section TMS and rTMS techniques in research, and bullet point Offline repetitive TMS contains the statement, "However repetitive TMS is very susceptible to the placebo effect." Unfortunately this statement is unreferenced. I'm wondering why the statement should be so. Couldn't you preform sham rTMS treatments on the subjects, including simulated noises? If the subject can detect the actual treatment it would be more difficult; you would have to knockout another portion of the brain you're reasonably certain how no relationship to the task you are studying. Does anyone have a reference supporting this statement? --Lostart (talk) 19:20, 26 December 2007 (UTC)

Firstly, simulated noises have been used in sham coils, but these do not provide the tactile scalp sensation of rTMS. I believe Prof Lisanby has produced a sham coil which also attempts to deliver a tactile scalp sensation by also electrically stimulating the scalp nerves to mimic the sensation. This coil is not widely available however. Also suprathreshold stimulation is very difficult to sham particularly if they involve the motor cortex as these forms of real stimulation produce very obvious arm or leg twitches. One could argue that a patient blind to real rTMS would not know what real rTMS feels like; this is a valid argument only in experiments which ensure that patients are blind to real rTMS and are assessed for blinding.

Also, see this reference which directly addresses why the placebo effect is very relevant when talking about rTMS:

Strafella AP, Ko JH, Monchi O. Therapeutic application of transcranial magnetic stimulation in Parkinson's disease: the contribution of expectation. Neuroimage. 2006 Jul 15;31(4):1666-72. Epub 2006 Mar 20.
Repetitive transcranial magnetic stimulation (rTMS) is a valuable probe of brain function. Ever since its adoption as a research tool, there has been great interest regarding its potential clinical role. Presently, it is unclear whether rTMS will have some role as an alternative treatment for neuropsychiatric and neurological disorders such as Parkinson's disease (PD). To date, studies addressing the contribution of placebo during rTMS are missing. The placebo effect has been shown to be associated either with release of dopamine in the striatum or with changes in brain glucose metabolism. The main objective of this study was to test whether, in patients with PD, the expectation of therapeutic benefit from rTMS, which actually was delivered only as sham rTMS (placebo-rTMS) induced changes in striatal [11C] raclopride binding potentials (BP) as measured with positron emission tomography (PET). Placebo-rTMS induced a significant bilateral reduction in [11C] raclopride BP in dorsal and ventral striatum as compared to the baseline condition. This reduction BP is indicative of an increase in dopamine neurotransmission. The changes in [11C] raclopride binding were more evident in the hemisphere contralateral to the more affected side supporting the hypothesis that the more severe the symptoms, the greater the drive for symptom relief, and therefore the placebo response. This is the first study addressing the placebo contribution during rTMS. While our results seem to confirm earlier evidence that expectation induces dopaminergic placebo effects, they also suggest the importance of placebo-controlled studies for future clinical trials involving brain stimulation techniques.


Regards. --Grushnik —Preceding comment was added at 13:12, 28 January 2008 (UTC)