In the last post, I put Explaining Pain (EP) through its paces on the Burns test of 5 criteria that need to be met if we are to accept a theory of how a treatment works. Well, today I am going to put graded motor imagery (GMI) through the same test, just to give you all an idea on how far we have to go. As we point out in the Graded Motor Imagery handbook (a blatant plug here) the theory behind GMI is that we are re-inhibiting disinhibited neurotags and gradually exposing sensitized neurotags. So, to test this idea, let’s run the Burns test:
1. Change in the proposed mediator correlates with change in the outcome. YES. Although it is difficult to assess, we can use markers of disinhibition and sensitization, which are left/right judgements and pain on imagined movements. In both cases, improvement correlates with pain reduction.
2. Change in the mediator precedes change in outcome. YES. The markers above precede the decrease in pain.
3. Early change in the mediator predicts later change in outcome but not the other way around. YES, but there is much in the decrease in pain that is not predicted by the improvement in those markers.
4. Change in the mediator is specific to the treatment. DON’T KNOW. There are some people in the control group in the clinical trials who improve their performance on left/right judgements but not many and the effect looks small. We need to design better trials to really test this one.
5. The relationship between change in the mediator and change in the outcome is not observed across treatments. DON’T KNOW. We don’t have enough data on this either.
So, unlike Explaining Pain, where we can be confident that changing pain-related biology knowledge contributes to the pain reduction effects of EP, there is not enough evidence to conclude that GMI works by reinhibiting and desensitizing. So, we need to do more research, with multiple measures and a credible control group. Anyone got a spare million dollars?
About Lorimer Moseley
Lorimer is NHMRC Senior Research Fellow with twenty years clinical experience working with people in pain. After spending some time as a Nuffield Medical Research Fellow at Oxford University he returned to Australia in 2009 to take up an NHMRC Senior Research Fellowship at Neuroscience Research Australia (NeuRA). In 2011, he was appointed Professor of Clinical Neurosciences & the Inaugural Chair in Physiotherapy at the University of South Australia, Adelaide. He runs the Body in Mind research groups. He is the only Clinical Scientist to have knocked over a water tank tower in Outback Australia.