Using a mirror to combat phantom pain

CNN has a story about a Navy neurologist who tried using mirrors to help soldiers from Iraq with phantom pain. Phantom pain is pain in amputees that is perceived to originate in the amputated limb. What causes it is not exactly clear although many theories exist. However, it is often refractory to pain medication (this is common in so-called central pain or pain originating in the brain), so it can be really difficult to make these patients feel better.

Dr. Jack Tsao, the Navy neurologist, had the idea that if you used a mirror to show the image of the opposing, intact limb where the missing limb should be, you could trick the brain into believing it was there and end the pain. Turns out it works pretty well:

Dr. Jack Tsao, a Navy neurologist with the Uniform Services University, was looking for ways to help soldiers like Paupore. He remembered reading in graduate school a paper by Dr. V.S. Ramachandran that talked about an unusual treatment for amputees suffering "phantom limb pain," using a simple $20 mirror.

The mirror tricks the brain into "seeing" the amputated leg, overriding mismatched nerve signals.

Here's how it works: The patient sits on a flat surface with his or her remaining leg straight out and then puts a 6-foot mirror lengthwise facing the limb. The patient moves the leg, flexing it, and watches the movement in the mirror. The reflection creates the illusion of two legs moving together.

"I was laying in bed and it just, all of a sudden, it felt like I was getting shocked," he said. "I called the nurse, 'cause I was like, 'What's going on?' " The nurse told him, "This is probably your phantom pain."

Tsao explains it this way: "It's the sensation that the limb is still present, and phantom pain in particular is the sensation that the limb is experiencing pain of some form."

That pain is intense, and often medication brings very little relief. For Paupore [a soldier from Iraq with an amputated leg], it was relentless.

"All of a sudden, it was like someone kept turning on and off the Taser, and my whole leg started twitching. ... I sat up, and I was holding on to my stump, and it just wouldn't stop. At that time, I was hooked up to the Dilaudid [a powerful narcotic], and I was pushing it. But you can push all the medicine in the world, and it won't stop it."

Paupore and 17 other amputees who joined Tsao's mirror therapy trial were randomly assigned to one of three groups. The first group used the mirror to look at their reflected image as they tried to move both legs. The second group used a covered mirror and did the same. And members of the third group were asked to visualize moving their amputated limbs.
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After a month of treatment, all of the patients in the mirror group had significantly less phantom pain. In the covered mirror group, only one patient experienced a decrease in pain, and for half of those patients, the pain worsened. Sixty-seven percent of the patients visualizing their limbs got worse instead of better. The pain decreased in almost 90 percent of the patients who then switched to mirror therapy.

It worked wonders for Paupore, 32. Within five months, he was off painkillers completely. Tsao says the difference is like night and day.

The cause of phantom pain is still under debate. The most current theory suggests that phantom pain is caused by the cortical reorganization. When the limb is amputated sensory information about where the limb is in space -- termed proprioception -- no longer comes into the brain. The brain compensates for this absence of information by reorganizing and in a sense over-representing areas that are intact -- they take over the area of the brain that used to represent the lost part of the body. During this process of reorganization, the patient can feel pain. (The subject is reviewed here.)

Let's speculate about why this mirror thing would work.

I think it is because the brain gets proprioceptive information directly from the limbs through receptors in the skin and muscle, but it also gets information about the limbs through the visual system.

You can prove this to yourself. Try taking a drunk test. Hold out your arms and touch your nose. Pretty easy. (...if you are sober, and consider you are probably reading this at work I sure as hell hope you are.) Now try doing that with your eyes closed. A little bit harder right. Your visual system assists the proprioceptive system in telling your brain where your limbs are in space.

What I think is happening with this mirror thing is that visual system is supplementing the proprioceptive system and tricking the brain into believing the limb is there. This helps alleviate the pain.

It shows that if you understand a system, a very simple solution can often achieve great medical results. Hive five to Dr. Tsao for thinking outside the box.