Retrained Brain Eases Phantom Pain
Shock therapy helps amputees with mysterious discomfort
THURSDAY, May 31, 2001 (HealthDayNews) -- Retraining the brain may drive away the phantom limb pain that haunts many amputees, new research shows.
A small pilot study by German researchers has found that a brief regimen of painless shocks can spur the sensory cortex to reorganize itself into a more normal pattern, quelling the fake limb pain better than conventional therapy.
Army Lt. Col. (Ret.) Richard A. Sherman, a leading expert in the field of phantom pain who is familiar with the German work, says sensory reprogramming could be an "excellent way to augment" biofeedback therapy that also has shown promise in helping restore normal sensation to amputees.
"But people have to be able and willing to learn, and most Americans would rather take a pill," says Sherman, a psychologist at the Madigan Army Medical Center in Tacoma, Wash. "Yet other than the behavioral treatments, there are very few medical treatments that have any degree of effectiveness at all. The behavioral treatments right now are the best available."
A report on the German study appears as a research letter in the June 2 issue of The Lancet.
Up to 80 percent of amputees complain of occasionally debilitating discomfort seeming to radiate from their missing body parts. The sensations can show up as burning or tingling, cramping or twisting and shocking, and each form is believed to be caused by different nerve problems.
Mounting evidence also points to post-amputation changes in the brain area called the primary somatosensory cortex. The region contains a map of neurons corresponding to clusters of nerve endings throughout the body. When your fingertips brush against a hot stove, for instance, nerves in the hand region of the map "light up." When a kiss grazes your lips, those that belong to the face activate.
After an amputation, or when nerves are severed by trauma, the cortical map gets scrambled. How the disruption contributes to phantom pain is not clear, but unwanted nerve signals seem to increase.
In the German study, a research team led by Herta Flor of the Central Institute of Mental Health in Mannheim tried to reorganize the cortical map by coaching nerves in the stumps of amputees. The researchers used a technique called sensory discrimination therapy, which tries to build nerve sensitivity the way lifting weights adds muscle.
Flor compared sensory discrimination therapy to conventional treatment, including painkillers, physical therapy and nerve stimulation, in 10 patients who'd lost limbs.
Over two weeks, five amputees received 10 rounds, each lasting 90 minutes, of high-intensity but painless electrical stimulation at the stump. As the study progressed, the amputees grew increasingly adept at pinpointing both the location and the frequency of the electrical stimuli, demonstrating that their stump nerves were becoming more responsive, the researchers say.
What's more, they reported less phantom limb pain at the end of the two weeks and at three month follow-up exams, while amputees receiving conventional treatment showed no improvement.
Looking at cortical reorganization with brain imaging techniques, researchers say that sensory discrimination produced marked changes in the region while conventional therapy did not.
"The alteration of cortical reorganization by behavioral means might be an effective treatment for phantom limb pain," write the researchers, who call for more studies using the same approach.
Neeraj Jain, a Vanderbilt University psychologist who studies phantom pain, says the German research "has a great potential to be used as therapy" for amputees and other patients with the syndrome.
One hurdle, however, is that "we really don't understand what are the mechanisms of brain organization," Jain says. "We know it happens, and increasingly it's becoming clear that this is the cause of the phantom pain." But without a fuller understanding of the way the nerves work, Jain says, "It will be hard to have a long-term cure for the phantom sensations."
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