for National Geographic News
For amputees suffering from phantom pain, a computer-generated cure might soon be at hand.
Virtual reality could hold the key to easing the often agonizing sensation of a missing limb that feels as if it is still there, experts say.
"Four of the five patients who used our virtual reality system reported significant reduction in pain," said Steve Pettifer, a computer scientist at the University of Manchester in the United Kingdom.
"If further tests prove this is a successful technology, it could be used in hospitals or by people in their homes."
Pettifer says about 80 percent of all amputees experience some discomfort associated with a phantom limb or limbs—often sensations of shooting pains or electric shocks.
Some people feel as if their limbs are curled up in impossible positions. Others sense their clenched fingers painfully digging into their palms.
(Related: "Feeling No Pain: New Form of Rare Gene Disorder Decoded" [December 13, 2006.)
Physicians have long known about phantom pain. Ambroise Paré, a 16th-century French surgeon, described it in soldiers with amputated limbs and suggested that the pain originated in the brain.
But even today it is not fully clear what causes the mysterious sensations, said Vilayanur Ramachandran, a neurologist at the University of California, San Diego.
"It is an old misconception," he said, that phantom pain is in the sensory nerve endings—the shortened nerves that, before amputation, would have reached all the way to the toes or fingers.
"When you remove the arm, there is a part of the brain that is not getting any [signals]. So sensory input from the face takes over where the arm used to be."
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