Easing Phantom Pain By Letting Missing Limbs Move

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Easing Phantom Pain By Letting Missing Limbs Move
October 10, 2016

Virtual reality, more often than not, is touted as a feature of state-of-the-art video games with headsets that allow players to see all around them, beyond the boundaries of their monitors.
 
But the technology’s potential extends beyond games. A team led by Masahiko Sumitani, head of the department of pain and palliative medicine at the University of Tokyo Hospital, has succeeded in using VR to treat phantom limb pain, a condition in which amputees or people with damaged nerves still feel pain from body parts that no longer exist.
 
Other researchers have tried to use virtual reality to treat phantom limb pain but none has produced a study explaining how it works — until now, according to Sumitani.
 
“We’ve found a mechanism through which pain can be reduced when patients are able to get an image of moving (their absent limbs) in their minds. This is something new,” Sumitani said. VR technology allows amputees to see and manipulate virtual images of their lost limbs. The virtual limbs move accordingly with the intact parts of the arm, allowing the images to take root in patients’ minds.
 
The team tried the treatment on eight patients who experience phantom limb pain in their lost arms. Six became capable of manipulating the virtual limbs in their minds, eventually relieving the pain.
 
The therapy lasted about 20 minutes each time, with the eight patients trying it for two to six months.

According to Sumitani, about 60 to 70 percent of people who have either amputated or lost feeling in their arms or legs suffer from the phantom limb pain. The sensations can range from something akin to a burn, a cut or being hit by lightning.
 
Sumitani said there are various causes of phantom limb pain, but the outcome of the VR therapy has identified one mechanism, in particular, that activates a distress signal from the brain.
 
“Human arms are originally designed to move, so when they don’t move, it is an unusual situation for the brain,” he said. “By sending the pain signal, we think the brain may be trying to say it is unusual.”
 
By allowing patients to realistically imagine moving their phantom arms or legs, they can thus feel a decrease in pain, he said. Sumitani also employed a method to gauge whether patients are able to create a mental image of moving their lost arms. They were asked to draw a continuous vertical straight line on a tablet with their intact fingers while trying to imagine drawing a continuous circle with the fingers of their absent arms.
 
If they are successful in creating a mental image of drawing a circle with their absent limbs, the image distracts the movement of the intact fingers, letting them get closer to the actual movement of their missing limbs drawing the circle. But if the movement of the patients’ intact fingers is not distracted, this signals that they are unable to move their lost limbs in their minds.
 
This method, Sumitani said, has helped a number of patients create mental images of absent limbs that they can move to relieve phantom pain. Alternative treatments such as taking medication, including tricyclic antidepressants and morphine, have not been nearly as successful despite improvements in quality, Sumitani said.
 
But aside from cutting-edge technology, Sumitani has also used simple items such as mirrors to help treat phantom pain. Called “mirror therapy,” this treatment involves placing a mirror beside the amputated arm or leg to help patients envision moving the absent body parts in their minds by viewing a reflection of the remaining limb’s movement.
 
Sumitani has been treating patients with mirror therapy since around 2005. When Yasuo Kuniyoshi, an engineering professor, at the university heard about it, he suggested that VR could be used as well.
 
After collaborating with Kuniyoshi, Sumitani’s hospital team kicked off VR therapy in 2013. The results so far show that VR is more effective than mirror therapy. “Patients can be more convinced with VR that their virtual limb is really part of their body,” he said, noting that some of the six patients who benefited made no gains under mirror therapy.
 
Still, virtual reality remains far from a perfect treatment. While it alleviated pain, the period of effectiveness varied among patients. For some, pain resumed after a few days; for others, it returned after several months.
 
And the degree of pain alleviation also differs between patients, he said. Another thing that needs improvement is the quality of the virtual limbs, which would make it easier for patients to immerse themselves in the experience of moving the imaginary phantom arm or leg.
 
Still, he sees great potential in the technology. First and foremost it’s not costly, unlike other high-tech medical treatments. Asked when the therapy would likely enter practical use, Sumitani said it could be as soon as two to three years.
 
And as the headsets become more commonly used, VR treatment won’t necessarily need to be done under formal medical direction, he said. Noting that patients should use it under a doctor’s guidance, Sumitani said the technology could provide a breakthrough in treating phantom pain.
 
“We hope that patients will be able to use it casually in their daily lives — like playing video games,” he said.

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