Oct 20 2008
Treating Coma with Magnetic Stimulation
There has recently been a number of news reports relating to coma, a fascinating topic and subject of active research, so there is no wonder that the public (and therefore the press) take an interest. Often, mainstream news stories focus on the notion of people “waking” from coma, or recovering from what was thought to be a permanent injury. This tends to hype the important, but subtle, progress that is being made.
The latest such story is of Josh Villa, a 26 year old gentleman who suffered a severe head injury in 2005 from a car accident. The injuries resulted in coma – the inability to be consciously awake – which evolved into a persistent vegetative state (PVS). By description, Josh was able to open his eyes but not respond to any external stimulation or interact with his environment. This meets the clinical definition of PVS.
Transcranial Magnetic Stimulation
His doctor, Theresa Pape, enrolled him is a study of transcranial magnetic stimulation (TMS). TMS uses strong magnetic fields to either induce or inhibit electrical activity in brain neurons. Therefore the technique can be used to turn off part of the brain, or stimulate it to be more active.
In this case TMS was used to stimulate the dorsolateral cortex in Villa – a part of the brain active in arousal. The hope was that by increasing activity in the dorsolateral cortex Villas entire brain would be more active, improving function. After 15 sessions of TMS over 6 weeks Villa was able to turn his head to someone speaking to him. After the treatments he contingued to slowly improve and eventually was able to say simple words like “help” and fragments like “erm”.Villa was then given another round of TMS treatments, but with no further improvement. He has since been stable.
Villa’s current condition is best described as a minimally conscious state, which is one notch above PVS. In fact, patients in a minimally conscious state are not uncommonly misdiagnosed as PVS if subtle signs of activity are missed on exam. The question now is – how to interpret Villa’s improvment?
It is not implausible that TMS can produce the improvements observed in Villa. Essentially what is happening is that a damaged brain, which is close to the line of just barely being able to generate wakefulness, is being stimulated so that it functions a bit more. Specifically, TMS may result in hypersynchronization - neurons firing together, which may reinforce their activity.
Increased activation has been shown before with deep brain stimulation - implanting electrodes in the brain that provide an extra kick to the cortex and make it a bit more active. The brain normally requires such activation to be awake, so such artificial stimulation may be replacing lost activation is some cases, or simply increasing the levels of activation in others.
While useful, such techniques should not be considered “healing” – they are not healing the brain, just squeezing a bit more activity out of it. Can TMS cause actual healing? Villa’s improvement persisted even after the TMS sessions ended (although he did lose a bit of ground, some improvement remained). Therefore his increased function cannot be attributed entirely to active stimulation, although hypersynchronization would endure beyond stimulation.
But an alternate hypothesis is the intriguing possibility that the stimulation increased repair of actual damage, perhaps by stimulating the activity of natural brain stem cells. Right now we have no way of knowing if this occurred.
It is also possible that Villa improved on his own, and would have improved the same amount even without the treatments. He was only a year out from his injury, well within the window where natural repair mechanisms could have produced the observed improvement in function. The TMS may have produced a temporary improvement over the background repair that was happening on its own.
The problem is that this is only one case, and with one case we cannot control for variables. What this study suggests is that there is a possible benefit from TMS and so further research is warranted.
TMS does have stronger evidence for benefit with neurological conditions such as Parkinson’s disease and tremor, but in these cases TMS is being used to inhibit brain activity, not increase it. The basic concept here is that there are systems in the brain where various structures provide feedback activation or inhibition to other structures so that a certain balance is maintained. If one structure is disease and not functioning, this can be partially compensated for by inhibiting another structure to help restore something closer to normal balance. Again – such an application does not “heal” damaged or diseased brain.
Magnetic Healing
I have been careful to discuss the mechanisms by which TMS may have clinical benefit, in patients with coma and other applications, partially because it is helpful to understand how an intervention might work. But also because magnetic therapy is a common type of unscientific or fraudulent treatment being sold to the public. Magnets are sold with a variety of medical claims, such as treating pain or arthritis.
TMS in no way relates to these dubious claims for magnet therapy. There are two primary differences. The first is that TMS uses a magnetic field much more powerful than the typical “refrigerator magnets” found in magnetic insoles or wraps. The plausibility of a biological effect from a magnetic field is directly tied to the strength of the magnet.
The second is that TMS is being used to affect the brain, which is an electromagnetic organ. While all cells have an electrical field potential across their membrane, the brain’s function depends upon cells evolved to use this electrical potential to actually conduct electrical signals. Therefore, the fact that magnetic stimulation can have a functional effect on the brain cannot be extrapolated to other tissues or organs.
Incidentally, the other tissue that uses electrical conduction as a key component of its function is muscle – heart, skeletal, and smooth muscle. The heart can also be treated with electrical stimulation – with a pacemaker or with cardioversion. Muscles can be stimulated electrically also. There is simply no analogy with the liver or pancreas, however. And (although I know many have pointed this out before) the iron in blood is not magnetic and does not respond to a magnetic field.
Details matter, and a therapeutic benefit from TMS of the brain for any specific indication should not be used to support TMS for other indications, or for magnetic therapy is general.
Conclusion
TMS is an interesting tool to explore brain function, and may have a therapeutic role as a means of providing stimulation to damaged brains to improve function. However, the data so far is preliminary. Further, there is no evidence to suggest that TMS actually heals brain damage.
I am intrigued and hopeful about recent research into treating coma victims, but results so far (from various forms of brain stimulation) have been modest. Generally speaking, patients improve one or two notches in brain function, and this may take them over a threshold where they can communicate better, but they remain profoundly neurologically damaged. It remains to be seen what the limits of brain stimulation as a therapeutic approach to coma are.
13 Responses to “Treating Coma with Magnetic Stimulation”
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jonny – yeah, I just decided to ignore the whole double-entendres while talking about “stimulation” and “arousal”.
In the realm of rampant speculation, would it be worth trying TMS with drugs that have been reported as possibly producing neuron generation such as Prozac.
Steven,
I was wondering: why/how does a severe head injury cause loss of consciousness? I can understand if maybe parts of the brain are literally not there because of the accident, or have been damaged severely and are thus “broken”.
The reason I ask, is because it appears as if the basic bodily functions that are regulated by the brain, are still pretty much intact during a coma (this is probably not true for all cases). I can also extend the question to being knocked out. Is the brain shutting down certain functions for protection of some kind? I assume Josh didn’t open his eyes because of a conscious choice. Is it just a reflex reaction?
Then a thought about TMS. Could running a current (whether electrical or magnetic) through someone’s brain cause them to think a specific thing? If we were to somehow stimulate the exact pathways needed, could we change/control what/how a person thinks? I’m thinking applications like rehabilitating criminals by “reprogramming” their brain or helping people with addictions, etc. There would be quite a number of applications for such technology.
TMS also has some promising case reports in chronic pain management but the whole idea seems just a bit too woo for me at the moment. I’m watching the research closely though..
I know when it comes to using magnets to accelerate bone growth, it is the oscillating nate of the EM field that is thought to help. Is that the same case as here?
[quote]I know when it comes to using magnets to accelerate bone growth, it is the oscillating nate of the EM field that is thought to help. Is that the same case as here?[/quote]
Yes. Or to be more exact it is the rate of change of the magnetic field that is important. The induced electric field is proportional to dB/dt.
If you move your head rapidly in a static magnetic field you can experience magnetophosphenes from the induced electrical fields stimulating the optic nerves.
Thank’s chris. I think that is an additional explanation for why fridge style magnets won’t work in this case.
Chris Noble: “If you move your head rapidly in a static magnetic field you can experience magnetophosphenes from the induced electrical fields stimulating the optic nerves.”
And if you drop some acid immediately before, you experience God.
@ superdave: To put it simply, and oscillating magnetic field creates an electric field, and a oscillating electric field creates a magnetic field. In this case they are basically using an oscillating magnetic field to create electric current deep in the brain (or other part of the body). In others words it is a non-invasive way to shock a specific part of the brain. It isn’t the magnet itself that is important, it is the electric current the magnet creates.
The physics behind it is no different than the magnets used to generate power in a copper wire in the turbines in your local power station (assuming you use anything other than solar power). Magnetic stimulation just generates the electricity directly where it is needed instead of having to send it over wires. Of course that is only the basic physics, in practice there are major differences due to the different properties of the magnetic field and different properties of the conductor (the brain), different shielding effects, and lots of other details that make the whole thing very messy in practice. But the basic principles remain the same.
Blackcat, thanks for the post. My point was though, that magnet pseudoscience does not involve changing magnetic fields because the magnets are usually fixed. This is in conjunction with the fact that the magnets are also very weak.
@ superdave: I understand, I was just explaining why the oscillation is so important.
Quick correction Steve, the phrase “Electrical field potential”, which I believe I’ve heard you use before, is not correct.
Electric fields and electric potential, although related, are not the same, and can not be mixed and matched. The derivative of the voltage (potential) is the electric field (i.e. E=-dV(x,y,z)/dt). In the same way that the derivative of velocity is acceleration (i.e. a=dV(v,x,y)/dt). So you would say, “the acceleration of the rocket” and not, “the acceleration velocity of the rocket.”
Keep up the great work! I’m actually majoring in Electrical Engineering, but decided to try to get into medical school to become a neurologist. You’ve had a big influence on that and I thank you.