At first, phantom pain was thought to be triggered by crushed or damaged nerves at the amputation site. Now, it is known that the discomfort originates directly in the brain. The part of the brain responsible for the missing limb now has no job, and begins to fire when other parts of the body are stimulated. In some cases, stroking part of a patient’s face will create the sensation of touching a missing limb.
That being the case, doctors have had some success at curing phantom limb pain by using mirror boxes to trick the brain into thinking the limb has been resurrected.
There are a couple of drawbacks to this treatment. For one thing, not all patients respond to the visual cues provided by the mirror. Perhaps more importantly, a person must have one completely sound and functional limb for the mirror to work.
Researchers from Chalmers University of Technology and Sahigrenska University Hospital in Gothenburg, Sweden have been experimenting with virtual and enhanced reality systems to get around both of these drawbacks. They use computer algorithms to turn signals from the muscles left at the amputation site into instructions for moving a virtual limb. Because the signals originate in the amputated limb, rather than the opposite side of the body, the sensation is more vivid. Also, no intact limb is required for the therapy.
Credit: Ortiz-Catalan et al., Frontiers in Neuroscience
So far, the scientists were able to bring relief to one patient who had suffered from phantom limb pain since losing his arm nearly 50 years ago. After working with the system once or twice a week for ten weeks, the patient reported his first moments of being completely pain free:
These pain-free periods are something almost new to me and it is an extremely pleasant sensation.I'm sure it is. And let's hope he and others like him can enjoy many more pain-free moments thanks to this technology.