London Press Service
Informs
HOW VIRTUAL REALITY RELIEVES
PHANTOM PAIN
For most people, just the thought of losing a limb through injury or illness brings a shudder of revulsion. But for the people who experience an amputation, the distress of the loss is often made much worse by a little-understood and highly painful after-effect that can cause severe suffering for the rest of their lives.
Doctors call this problem phantom limb pain and it affects at least four out of five people who lose an arm or a leg or a part of one. For some it brings annoying discomfort; for others, bouts of crippling pain and life-degrading anguish.
The worse the pain, the harder the sufferer finds it to learn to live without the missing limb – and the less likely the sufferers are to use an artificial limb, restricting their well-being still further and leading to higher levels of depression.
This extraordinary after-effect of amputation can respond to drugs such as painkillers or even, in extreme cases, major surgery such as deep-brain stimulation that links a chest-implanted electronic control box to an electrode in the area of the brain thought to be responding to phantom pain. But the success of these methods is often limited and short term.
Now, a team of scientists in the United Kingdom has achieved what could be a crucial step towards finding a way to alleviate phantom limb pain (or PLP) widely, affordably and perhaps even permanently.
In a trial pilot study involving five sufferers, researchers at the University of Manchester linked patients to a virtual-reality imaging system that gave the sufferers scope to “see” their missing limb again. The positive reactions and results they experienced, sometimes almost immediately, startled the scientists and delighted the people involved, one of whom has suffered from PLP for 40 years.
So phantom limb pain is a significant cause of distress for a very large number of people, very often people whose quality of life is already at a low ebb for various reasons.
Dr. Pettifer and his colleagues use their remaining physical limb to control the apparent movements of a computer-generated “virtual” limb that appears in 3D computer-generated images to take the place of their amputated limb. They can use their left leg, for example, to control the movement of their virtual right leg – complete with its virtual right foot.
Peace of mind: Peter is one amputee taking part in a pilot study to find a new way to ease the anguish of phantom limb pain. He reported a big reduction of pain after using this Manchester University computer-generated imaging system that enables him to “see” and “move” his missing arm. Spurred on by this success, the UK scientists will begin a wider trial of the technology later this year.
Earlier research by scientists using a mirror-box had shown that pain could decrease when the brain of a PLP sufferer is tricked into believing it can see and move a phantom limb. By taking the functions of a mirror-box to a new higher computer-generated level, the work of Dr. Pettifer and his colleagues is attracting scientific interest across the world.
Scientists in this field have long studied the causes and effects of PLP without effectively being able to achieve any long-term easing of the problem that can affect amputees of both sexes and all ages and regardless of the limb they have lost. No-one fully understands what causes these mysterious sensations, although latest evidence suggests they are psychological or neurological in origin, rather than physiologically triggered as believed earlier.
Each person in the trial used the system between seven and 10 times over the course of two to three months. The sessions lasted about 30 minutes and involved wearing a special headset. Upper-limb amputees were fitted with a special data glove and had sensors attached to their elbow and wrist joints, while scientists monitored their head and arm movements. The group included three arm amputees and two leg amputees who had lost their limbs between one and 40 years ago.
In their tests the amputees used their phantom limb to undertake simple tasks such as tapping a touch-pad, gently striking a VR airborne table-tennis ball or following a floating ball with a finger-tip. Batting the ball proved their overall favourite task, rapidly easing the pain felt by several in the trial.
Encouraging though these initial results are, Dr. Pettifer and his research colleague and project leader Dr. Craig Murray of Manchester University’s School of Psychological Studies acknowledge they are still very much at the basic stage of their work.
“There are so many types of PLP that we need to do much more research into the effectiveness of virtual reality systems,” admits Dr. Pettifer. “Although our research is extremely encouraging, there is still a vast amount we do not know, for example about the effectiveness of different virtual graphics for different people, or whether the benefits of VR will be felt long-term, or indeed whether certain VR environments could actually make the problem worse.
“It would be valuable also to be able to gain a more objective measure than just the perception of pain. For example, we could map the response to brain function by using MRI (magnetic resonance imaging) techniques before and after each treatment.
“But if further tests prove this is a successful technology, it could be used widely in hospitals or by people in their own homes, because normal PlayStation-type equipment can easily run the software,” he added.
Such easy accessibility to pain-easing therapy could one day lighten the lives of PLP sufferers everywhere and give them more confidence to use artificial limbs to help themselves return to near-normal lives.
By John Hutchinson
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