rTMS and chronic pain: Our two penny’s worth

Some of you might have heard of repetitive transcranial magnetic stimulation (rTMS) and its use in chronic pain. Basically rTMS uses magnetic fields to generate electrical currents within the brain. This is a direct way of altering neuronal firing or excitability in the brain and a number of research groups have been investigating whether it might be used to treat chronic pain by altering pain processing in the brain. To get an idea of what it’s all about check out this section of the BBC’s Horizon programme “The Secret World of Pain”.

While that video is emotionally compelling and at face value looks really promising, I lost count of the number of ways in which the placebo effect might be being ramped up in that interaction. In fact I personally felt that the programme did not really offer the viewer enough balance or caveats there. So what does the best evidence tell us about the efficacy of this technique? For a change we get to talk about our own research because after carrying out a Cochrane review on this very topic we have just written a commentary in the journal PAIN® that discusses the current state of the evidence for rTMS in chronic pain management.

Our review found a bunch (19) of small studies of rTMS. Overall the data was quite varied but when pooled it suggested a small effect. When we broke the data into pre-planned subgroups we found a small short-term effect on pain of single doses of high frequency rTMS applied to the motor cortex. Great news – it seemed to work better than sham (placebo) stimulation. But as usual there were reasons to be a tad less cheerful. The effect was small and while it tickled the feet of clinical importance it didn’t clearly hit that target. There were also problems with risk of bias, particularly the tricky challenge of effectively blinding the studies, and we know that these issues tend to exaggerate effect sizes.

In fairness to rTMS these were single-dose one-off treatment studies. Maybe more doses would be more effective. Also they almost all recruited patients with severe neuropathic pain that didn’t respond to anything else either, so not the easiest pain to influence. When we looked the few studies that delivered multiple doses the results were conflicting and inconsistent and there really aren’t enough of them to make a confident judgement.

The point that we make in our commentary is that the evidence does suggest that rTMS might modulate pain, but this data has its problems, the studies are small and the evidence is a mixed bag of quality. There are more small, exploratory studies being published regularly, all justified by and based upon the initial promise of the earlier work but what is really needed is for researchers to take a nice big sample, deliver a good robust course of rTMS treatment using the parameters that look most promising right now (high frequency stimulation to the motor cortex), measure their outcomes over a decent time span, and all of this with good tight methods and better blinding. Sounds easy (but of course it never is)! But without this effort the next time we update our Cochrane review we might still only be able to say “maybe, maybe not”.

Neil O’Connell

Neil OConnell 150 rTMS and chronic pain: Our two penny’s worthAs well as writing for Body in Mind, Neil O’Connell is a researcher in the Centre for Research in Rehabilitation, Brunel University, West London, UK. He divides his time between research and training new physiotherapists and previously worked extensively as a musculoskeletal physiotherapist. He also tweets! @NeilOConnell

He is currently fighting his way through a PhD investigating chronic low back pain and cortically directed treatment approaches. He is particularly interested in low back pain, pain generally and the rigorous testing of treatments.

About Ben

BWand 120x150 rTMS and chronic pain: Our two penny’s worthBen Wand is currently the coordinator of musculoskeletal studies for the Physiotherapy program at the University of Notre Dame Australia. He completed his original physiotherapy degree, as well as post graduate qualifications in sports science and manipulative physiotherapy in Sydney. He undertook his PhD at Brunel University in London on physiotherapy management of acute low back pain. His current research interests include the role of central nervous system dysfunction in chronic low back pain and physiotherapy management of chronic spinal pain.

References

rb2 large gray rTMS and chronic pain: Our two penny’s worth

O’Connell N, Wand B, Marston L, Spencer S, & Desouza L (2011). Non-invasive brain stimulation techniques for chronic pain. A report of a Cochrane systematic review and meta-analysis. European journal of physical and rehabilitation medicine, 47 (2), 309-26 PMID: 21494222

O’Connell NE, & Wand BM (2011). Repetitive transcranial magnetic stimulation for chronic pain: Time to evolve from exploration to confirmation? Pain PMID: 21703764

Comments

  1. Hi Neil,
    I was in your talk at the WCPT conference in Amsterdam. I had read some papers about the effects of rTMS and I was interested in knowing it was evidence based. Your talk and now your post is veru clarifing. There are always someone trying to send as miracoluus devices to terat chronic pain
    Thanks for your systematic review

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  2. Neil O'Connell says:

    Thanks Rafael, although I should stress that I am not suggesting that these researchers are trying to peddle a fake treatment or that it doesn’t work, just that the current evidence is not strong. Bias in research is separate from fraud and much of the risk of bias in these studies was inavoidable at the time that the studies were performed. Time will tell

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  3. Lynley Bradnam says:

    Hi Neil,
    Met with Lorimer today and he altered me to this blog (yes I’m in Adelaide now). Always good to get your take on these things. I’m taking it home to read tonight. Be good to chat some more, Say hi to everyone at Brunel,

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    Neil O'Connell Reply:

    Hey Lynley! Good to see you here, you might like some of the posts on acupuncture….

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  4. Tim Vaughan says:

    hey:

    did you folks (Ben and Neil) get my diatribe about researchers who criticize criticize criticize?

    timv

    [Reply]

    Neil O'Connell Reply:

    Hi Tim,

    I don’t think I have seen that diatribe. If you have concerns regarding this post I would be happy to hear which points you feel are unnecessarily critical or one sided.

    [Reply]

  5. Tim Vaughan says:

    Here’s the diatribe!
    Neil:
    Get ready for a little rambling criticism. I’m a long-term chronic pain patient. Maybe you don’t realize that this blog is read by patients — but it is.

    “Publish or Perish” research scientists often make me laugh. You’re so into criticizing. I know in your profession, it is part of what you guys do, but as a patient and applied scientist (with degrees in the sciences and engineering ), it often bugs me.

    I’ll have to say that’s one of the many things I like about Lorimer — he keeps the criticizing to a minimum – a rare, positive research scientists who is definitely into problem solving and thinking out of the box.

    Personally, I found the video to be invaluable to show to the general public, family, friends. There’s also a recent TED talk which I also use to show to people who are clueless about the reality of nasty chronic pain like CRPS.

    I suspect wanted to blog on your rTms research review paper, and the BBC video gave you a opportunity. But, I want you to consider — did the BBC video present itself as a scientific research paper? Of course not. To my recollection, the video did not say that rTms was a solution, rather said it was a emerging research area that was promising, not unlike mirror therapy a decade ago (still?). It was a rare video made for mass consumption highlighting the existence and misery of very serious chronic pain syndromes and research being done to try to help these patients. I suggest praising this video — it helps inform the public! — and inform the people that hold the purse strings for research!

    I watched the entire and found it to be quite moving. It also put me into full mode trying to do some research on TMS/rTMS. I found what you found — it was obvious that researchers are still trying to get down what & where & how to use rTMS on chronic pain, but that’s the scientific process isn’t it (as is scientific criticism)? However, in a blog, consider a different approach. Maybe explore the different ways that other researchers are using rTMS and suggest different options that might be tried in future research.

    As far as the woman in the video — has anybody followed up with her to see how she has done? I’d love to know about that. What a great subject for a blog. The visual image of her having even a short temporary relief from the pain in her arm is riveting and put tears in my eyes.

    Respectfully submitted,
    Timv
    Tim Vaughan
    Fort Collins Colorado.

    [Reply]

    Neil O'Connell Reply:

    Hi Tim,

    I’m pleased to see patients reading the blog, and in many ways I feel that that justifies what I have written a little more. To be clear I was invited to write this blog post and the actual editorial we discuss, I don’t normally blog about my own research and it wasn’t an exercise in “publish or perish”, in fact I am of the opinion that systematic reviews are amongst the most important research approaches we have rather than an exercise in publishing for the sake of it.

    I’m glad that you found the video helpful. I take your point that criticism can sometimes appear arbitrary and unnecessary but I beg to differ. You see in health research it is very difficult to get close to the truth, particularly in terms of the effiacy of a treatment, and particularly in a condition as hard to pin down and measure as pain. The aim of a Cochrane review is to give as balanced a view as possible of the evidence base of a given treatment, and I feel that that is what we have done.

    I did not suggest that the video aimed to be a scientific paper, although it is part of BBC’s flagship science programme. All I wanted to see was the hope on display tempered by a little more caveat. I happen to think, as a clinician as well as a researcher that false hope is counterproductive and that given the state of the therapy market in pain we need to be very cautious in how optimistically we push new approaches ahead of quality data. But that is just my view.

    You might notice that we do indeed offer a suggestion for what the research priorities should be in rTMS pain research now. We do not suggest that it does not work, or that further rresearch should not continue. We feel that this way researchers and patients alike could be best informed about whether this will be a good option, and we also feel that until this is done we simply won’t know. I do not think that this represents unconstructive critique.

    As a scientist yourself you know that science thrives on critique. What I try to do in my blogs is to present a balanced view of the evidence, but of course balance can be a matter of judgement.

    [Reply]

  6. Anything which raises awareness of CRPS and other chronic pain conditions is surely a positive step in the right direction.

    [Reply]

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