New virtual reality tech eases phantom limb pain

Scientists have developed a new virtual reality (VR) technology that can relieve the sensation of phantom limb pain by tricking the brain into thinking that it is still in control of a missing limb.
If a hand, an arm or a leg is amputated due to accident or disease, eight out of ten amputees experience a feeling of discomfort in the limb that is no longer there. The phenomenon is called phantom limb pain.
"The tactile representation of different body parts are arranged in the brain in a sort of map," said Bo Geng, from the Aalborg University in Denmark.

"If the brain no longer receives feedback from an area, it tries to reprogramme its signal reception map. That is the most common conception of how phantom limb pain occurs," Geng said.
Tests have shown that phantom limb pain can be relieved if the brain is tricked into thinking that the amputated limb is still attached to the body.
By placing a mirror at an angle in front of the chest you can create the visual illusion that the body is symmetrical.

If you then pretend to do the same movements simultaneously with both hands, the brain in many cases can be convinced that it is in contact with an amputated hand.

The method has proven effective in a number of amputees and is the foundation for the new VR technology.
By using VR it is possible to create an experience of being present in a three dimensional world where you can move around freely, grab things and interact with them, researchers said.
"The mirror therapy has some limitations because you have to physically sit down in front of a mirror, do the same movement in a confined space with both hands at the same time and keep your eyes on the mirror. The illusion can easily be broken," Geng said.
"With virtual reality there is a much better chance of creating a convincing alternative reality," she said.

In the new method the patients have to put on VR goggles and a glove. At the same time, small electrodes are placed on the residual limb, known as the stump.
By stimulating the stump with tiny electrical impulses, researchers try to recreate the sensation of the phantom hand.
The amputee plays a number of different VR games that involve doing the same thing with both hands such as grabbing a pole that has to be twisted into different shapes or pushing different virtual buttons.
In the virtual reality it feels exactly as if you were using both hands, researchers said.

"Even though a person who has had a hand amputated can no longer see it, in many cases he or she can still feel it. This sensory conflict may be interpreted by the brain as pain," Geng said.
"With this new method we try to overcome that conflict by providing an artificial visual and tactile feedback and in that way suppress the pain," she said.
The new approach underwent its first clinical test at the China Rehabilitation Research in Beijing last year.
Two out of three amputees felt their phantom limb pain ease whereas the third one experienced a decrease in the frequency of phantom limb pain attacks.