How pain is cured by looking in a mirror; painting by numbers

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www.TimesOnline.co.uk, originally uploaded by rsdscrpsnews.

How pain is cured by looking in a mirror;
Science Notebook by Anjana Ahuja
I HATE missing a step, and not just intellectually. That stumble at the bottom of the stairs, when the ground beneath one’s feet doesn’t conform to expectations and brain and body are uncoordinated for an instant sends a shiver of surprise through me.

Through a series of ingenious experiments scientists have begun to theorise that pain may be an outward sign of a similar brain-body mismatch. The so-called cortical model would help to explain such enigmas as phantom limb pain, in which an amputee is tormented by aches in a missing limb. It would also illuminate why people frequently report pain in the absence of an obvious clinical cause. Intriguingly, researchers have discovered that the pain can be cured by using mirrors.

Dr Candy McCabe and Professor David Blake, at the University of Bath, enlisted patients with a condition called complex regional pain syndrome. This describes an ache that sets in after nerve injury; it lingers and often escalates long after the break has healed. The agony can be so excruciating that patients request an amputation.

McCabe angled a full-length mirror up against each patient, so that the damaged side was out of view and only the healthy side was reflected. She then asked them to do symmetrical exercises, such as lifting both arms. Half the patients reported a reduction in pain. The effect could not be replicated using a white board — suggesting that relief lay, somehow, with the reflection.

Since the damaged limb is hidden, and replaced by the mirror image of the healthy one, McCabe speculates that the brain is fooled into believing that all the limbs are moving normally. The brain-body mismatch disappears — and the pain with it. “It sounds bizarre until you see it, and then it’s fantastic,” she says. The research, funded by the Arthritis Research Campaign, is published in Clinical Medicine.

McCabe explains that injury disrupts communication between brain and limb — in other words they do not “talk” to each other as they normally do. “Plaster casts also reduce the sensory input from a limb. In some people — we don’t know who or why — the system doesn’t correct itself after healing. We think that pain is the alert mechanism, and it then sets off other alert mechanisms, so the area becomes hypersensitive and even more painful.

“But the mirror gives the brain a normal-looking arm, and gives the patient the feeling that their limb belongs to them again.” The mirror exercises apparently help to repair the broken loop between brain and limb — some patients on this therapy find that their pain disappears permanently.

McCabe has also found that when healthy volunteers carry out asymmetrical mirror exercises — in other words, the hidden limb moves in a way that does not correspond to the reflected one — they sometimes experience aches, numbness, pins and needles and a cold sweat.

The findings have important implications: new plaster casts for old injuries may worsen, rather than ease, discomfort; and patients afflicted by mysterious pains will be relieved to know that, in a manner of speaking, their ailment is not all in the head.

Original Article: http://www.timesonline.co.uk/article/0,,20909-1860449,00.html

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