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The Cure For Phantom Limb Might Involve Playing Trackmania

The phantom limb effect - and the pain and discomfort often associated with it - is, for the most part, still a mystery to the medical community. No one's quite sure what sort of misfiring neurons cause the effect, nor are they entirely certain what to do about it. Unpleasant news for amputees, who often have to deal with searing pain, stabbing muscle cramps, and itches that are impossible to scratch.

Although we're not getting much closer to understanding the cause of phantom pain, one Swedish researcher believes he may be close to discovering a cure - and it involves video games. Chalmers University of Technology PhD candidate Max Ortiz-Catalan has developed an experimental muscle mapping treatment which uses augmented reality and video games to basically trick the brain into thinking its missing arm is back. The technology makes use of probes that detect muscle movements at the point where an amputees arm is removed, at which point those movements are deciphered into a computer-generated image of the missing limb. 

In the first phase of treatment, carried out in weekly two-hour stints, Ortiz-Catalan has the patient 'move' their missing limb. While they do this, they're shown a video which shows the reattached arm moving in realtime and responding to their actions. The next phase has Ortiz-Catalan attaching the same electrodes, at which point the patient is instructed to steer a car in Trackmania using their missing arm.

So...wait, this treatment basically fools the brain into thinking it's still got all four limbs? Wouldn't that just exacerbate things? How could that possibly work? 

We're...actually not entirely sure how it works, but for some reason, it does. The patient in the technology's first clinical trial was a young man who'd spent decades dealing with constant, burning phantom pain on his missing limb. Within weeks of starting the treatment, the pain lessened considerably, and the phantom limb - which to the patient, felt like he was clenching his fist - gradually relaxed to match the computer image he saw on the screen of an arm with an open hand. 

Like I said, we've no idea how this could possible work - but Ortiz-Catalan has a theory. 

"When you have a part of your body amputated, it doesn't matter if it's a limb, a nose or a breast, some people have sensations of still having that part of the body, phantom sensations," he explained to Polygon. "When people perceive pain in that part of the body it's called phantom limb pain. It feels like burning or stabbing, or maybe like the wrist is extremely bent back. Nobody knows the underlying mechanism of phantom pain."

"One theory is that it has to do with the cortical map, which has a representation of every part of your body for motor control and sensation. What researchers have found when people are missing a part of the body, that part of the body stops being used for motor control and there is a reorganization in that cortical area, and something happens in that reorganization that causes pain. We think the pain is related to the cortical reorganization."

Ortiz-Catalan's treatment has its roots in something called mirror therapy, which made use of a mirror box that allowed a patient to 'see' a reflection of their missing limb. 

"The visual feedback and the motor execution helped to restore the cortical map, which gets rid of the pain," said Ortiz-Catalan. The problem with mirror therapy, he continued - adding that this problem isn't present in the AR treatment - is that it doesn't really work that well for patients with missing legs. 

"In ours you don't need to have your other limb because the movement comes from signals from the stump," he said, adding that, "You need to work out the muscles in the stump to make it work. With augmented reality, you see yourself and we put the limb where the limb is missing." 

In addition, Ortiz-Catalan's treatment allows him to map the impulses in a patient's limb. This allows him to check what they feel they've control of in the missing limb. Some patients are able to only move their little finger or their wrist; others have control over their whole arm. Every patient, he explained, has a different sensation. By asking them to run through different motions, he can see both how much control they have and how accurate his algorithms are at predicting signals. 

Only once those signals are correctly mapped are the patients instructed to play Trackmania

"We ask them to play games using the missing limb," he said. "At the end of the day, making them use that brain area, which they are not used to using, potentially helps to restore the brain map." 

While Ortiz-Catalan admits that he could design a system to allow his patients to play more complex games like Call of Duty, he feels it wouldn't be as beneficial. According to him, racing games are ideal because they generally involve full motion of the wrist and arm. Not really the sort of experience you'd get from a more traditional game.

In the long-term, Ortiz-Catalan hopes to get his technology into hospitals around the world, and perhaps even into people's homes to allow them to carry out the treatment on their own. He also notes that he could see his methods being used for other conditions, such as strokes or spinal cord injuries. He'd be perfectly willing to collaborate with international researchers to make this happen. 

"It's a rehabilitation tool for neuromuscular rehabilitation," he said. "It makes movement fun to do. If you have an injury and they tell you to move the shoulder 20 times, you may not do that. But what if instead of that you could hook up this system, and every time you do your rehabilitation you're driving a car? It now is very common that patients try to recover with video games, but they're more focused on achieving the goals of the game and not the rehab."

Although we're not really any closer to understanding how phantom limb pain actually works, with technologies like Ortiz-Catalan's, we could very well end up that much closer to ensuring it'll no longer be a problem. And people say video games don't do any good. 

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Nicholas Greene
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