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Dangers of transcranial magnetic stimulation of the brain

  1. May 24, 2014 #1


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    When transcranial magnetic stimulation (TMS) is applied to certain areas of the brain, once can induce movement of a body part or interfere with speech. This is because the generated electric field influences neurons.

    The use of TMS at the sensorimotor cortex is quite harmless, but what are the dangers when it is applied to the brain stem? That brain region controls vital functions, such as heart rate and breathing. Could TMS be dangerous when improperly applied?
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  3. May 24, 2014 #2

    Simon Bridge

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  4. Jul 18, 2014 #3
    Iv always wondered if the over stimulation of certain areas using this method would lead to depressed function without it. Similar to drugs (stimulants) that it requires a another dose to get back to the "norm".

    I haven't been able to find any literature on it though...

    Unless I'm over looking something (typically the case) I think the long term effects should be researched further before people start trying to enhance their numeracy.

    This mentions some effects of magnets on the brain, it's pretty interesting.
  5. Jul 18, 2014 #4
    Well, of course, anything could be dangerous if improperly applied. But probably not TMS. It doesn't penetrate more than a couple cm below the skull. And I don't know anyone that's trying to target the brainstem. Personally, I don't think the technique is much more than a parlor trick. It's effectively analogous to Wilder Penfiled's mappings of the temporal lobe in the 40's, only non-invasive and less detailed.
  6. Jul 18, 2014 #5
    I looked at this site, and what are you going to say about it? To me it looks like modern-day snake oil salesmanship. An updated, "designer" version of electro convulsive therapy (ECT) from the early days.

    The thing is that ECT works, temporarily... But at what cost long term? TMS is still new and, as with the vapor smokes, are probably pound for pound less harmful. However, history has shown that when you make a drug or "remedy" 50% less harmful, typically you increase the rate of consumption of that remedy by 100+% So, you do the math, its all relative.
  7. Jul 21, 2014 #6
    Last edited by a moderator: May 6, 2017
  8. Jul 21, 2014 #7
    Isn't that what I said in my last post? It does work. In fact, the patients can't wait to get zapped, many love it and line up for it. But it does come at a cost, most notably short term memory loss: http://www.ecttreatment.org/ect-faq.php

    I'm really not so current (pardon the pun) with research into TMS, so maybe I'm not the best guy to ask, but it just seems to me that, whether it's ECT or TMS, bluntly sending current into your brain to cure some ailment should be a last ditch, extreme solution.

    In the old days, R.G. Heath planted self-stimulation electrodes in the septum of humans as an experiment in the treatment of depression. It worked. The humans banged on that button all day, just as the rats do in a Skinner box. Personally, I would rather have an electrode planted in my septum to cure depression than participate in ECT or TMS. It is much more specific and targeted. They call TMS "noninvasive", but if it's sending energy into your brain to depolarize neurons, trust me, it's invasive.

    Incidently, madness, this ECT that you are defending has an ugly cousin called electroconvulsive coma. This is what Walter Freeman used to to do to his patients before he gave them a trans-orbital lobotomy. If you want a demonstration, fast forward to 1:30 into this youtube video. Warning: this is not for the squeamish. I'm not joking, if you don't have the stomach for it, don't watch.

    But it is reality, this did happen in the 40's and 50's, and even 60's. Freeman made it a pilgrimmage of his, driving around in a "loboto-van" from state to state performing the procedures and training local doctors to do the same. I personally know his son, Walter J. Freeman III, who in my mind is the greatest neuroscientist that ever lived, and a mentor of mine. He said that institutions at the time were flooded with people that the admin had absolutely no idea how to treat or care for, and electroconvulsive shock, lobotomy, and Thorazine were really some of the only treatments they had around for the severely troubled patients.

    This is a fascinating story, and if you want read a great book on the subject, pick up "Great and desperate cures" by Elliot Valenstein: https://www.amazon.com/Great-Desperate-Cures-Psychosurgery-Treatments/dp/1452820422

    Several year ago, I was writing a paper for a book chapter and, in the process of doing my research, found out that they are still doing lobotomies in several countries, believe it or not. I have to say I was shocked (again, pardon the pun, not intended). The difference with these contemporary "designer" lobotomies, though, is that they target the orbito-frontal cortex rather than the ventro-lateral and dorso-lateral cortex, which is the frontal-cortical region most specifically involved in higher human cognitive processes. So, although as a general rule I consider psychosurgery "butchery," I am not totally opposed to orbitofrontal resection for extreme cases. It is a procedure that won't leave the patient "zombified." If they do it right.

    So, to bring this back to TMS, I would just say don't be cavalier about it. I know people in the field that have had their motor cortex's TMS'd, again, as much of an adolescent parlor trick, and I guess that's OK. But my guess is that this isn't going to be the miracle remedy for whatever one may want it to be or that many are maybe hoping it will be.
    Last edited by a moderator: May 6, 2017
  9. Jul 21, 2014 #8
    I posted this link (April 23, 2011) on non-invasive direct current cortical stimulation. I haven't looked at any more recent published papers on non-invasive cortical stimulation..

    Last edited: Jul 22, 2014
  10. Jul 22, 2014 #9
    You would rather have an electrode implanted inside your brain than have a magnetic field generated near your head? Are you serious? TMS is performed routinely in psychology experiments on healthy participants, because it is basically harmless when used properly.
  11. Jul 22, 2014 #10
    Yep, that's what I said.
  12. Jul 22, 2014 #11
    Do you feel the same way about magnetic resonance imaging, diffusion tensor imaging etc.? All of these are involve the penetration of magnetic fields into neural tissue.

    I dont think you can reasonably argue that it's safer to open up a persons skull and physically implant an object into the neural tissue than to pass a magnetic field from outside of the skull.
  13. Jul 22, 2014 #12
    I'm not trying to be trite/evasive, madness, but I'll let you in on a little secret... At the end of the day, nothing really matters other than what stimulates your meso-limbic medial forebrain bundle (MFB). That's kind of the ugly truth of life. So if you have an electrode planted in there that you can control, it might be a little less ugly.

    Monique, the OP here, had her initial question relating to the effects of TMS on the brainstem. As I mentioned in a earlier post, I'm not current on this research and I am actually interested. If they can TMS my MFB, I'll show up tomorrow. I don't have the time right now to research it, so if you have some info, please share.
  14. Jul 22, 2014 #13


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    "When used properly" kind of introduces no true scottsman fallacy. The real question is how often it's not used properly (in a way that leads to injury) vs. other methods.

    I don't know one way or another what the safety statistics are for all the different imaging and manipulation techniques, but I think the question of merit is about how things actually work out in practice.

    As to EM fields on the brainstem, the Pre Botzinger complex regulates rhythm in breathing. If EM waves can mess with the firing rate of the PBC, then it's possible they could mess with breathing. However, we can breathe consciously and I don't know how independent that is of the automated brainstem processes. Maybe during TMS to the brainstem, conscious breathing would naturally take over. Or maybe there's other autonomic fail safes.

    I know that in the study of SIDS, there's a model where the serotonin system (in the brainstem) fails, but in SIDS survivors, a GABA system can take its place.
  15. Jul 22, 2014 #14
    This is obviously true, all I was saying is that its unreasonable to claim that intracranial, subdural implants are safer than TMS. Masters students with several days of experience are allowed to practice TMS on willing members of the public. It takes decades of training as a neurosurgeon and a patient with a long history of resistance to other treatments before implants would be considered.
  16. Jul 22, 2014 #15


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    Understandable. Though the comparison is somewhat unfair given the surgical requirement of the implant. Ignoring the surgical part, my assumption is that the implants are more precise and controlled, whereas TMS is more of a random bombardment.
  17. Jul 22, 2014 #16
    I have heard talks at conferences from neurosurgeons who perform deep brain stimulation, from which it would be reasonable to conclude that surgical implants are basically also a "random bombardment". Remember that TMS has millimeter precision, while the level of uncertainty about the correct location to target while performing surgeory is fairly large, and usually boils down to trial and error on any given patient.
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