Wednesday, 20 January 2016

Phantom Limb Syndrome: Haunted by the Hand that Isn’t There

Your brain and the rest of your body are connected in ways that are sometimes tough to comprehend. It’s not something we think about as we go about our lives, but the sensations we feel in our hands, feet, face, chest, and everywhere else represent a partnership that is kind of amazing. Even as you read this, your brain and the parts of your body in contact with whatever you are sitting, standing, or leaning on are producing a symphony of experiences that ranges from comfortable to horribly painful. But occasionally, even the most practiced of orchestras can slip out of tune. When that happens between the mind and the body, the results can be downright perplexing.

Imagine that you are hard at work on your wheat farm when, all of a sudden, your tractor hits a bump, turns over, and crushes your arm. You are rushed to the hospital by your loyal assistant farmer, where you learn that the damage to your arm is too severe and it will need to be amputated. You are sedated, wheeled into an operating room, and wake up sans limb. The speed with which this can all happen is way beyond what your brain is able to deal with, both emotionally and structurally. The upshot is that for the vast majority of people who lose some part of their body (some doctors estimate up to 80%), the experience of being fully intact does not end with amputation.

Phantom limb syndrome is something people have been dealing with since we began lopping off each other’s arms and legs, and was first described by French surgeon Ambroise Paré in 1552. Paré worked with soldiers who lost limbs in battle, only to complain of sensations ranging from pins and needles to excruciating pain in parts of their body that no longer existed. Over the centuries our understanding of this affliction has evolved, but is still far from complete. What we know is that the problem stems from the way our brains map our bodies.

As we’ve already learned, when a part of your body (ex. your hand) touches something, neurons beginning at the point of contact travel through your body, up your spinal cord, and into your brain. The brain interprets the contact and produces an appropriate feeling (pain, heat, cold, etc.) that you experience at the point of contact, even though it is all going down in your head. There are physical pieces of your brain that correspond to every part of your body, internal and external, and just because you lose one of those parts to a tractor or a lion or whatever, doesn’t mean that the part of your brain that is partnered to it also goes away. As that piece of brain matter tries to make sense of something that doesn’t exist, the confusion results in the feelingof pain.

So how can we treat pain in a non-existent part of the body? The short answer is we basically try everything, giving preference to treatments that don’t involve surgery or causing any more harm. Therapies begin with massaging the area of amputation and extend to the use of painkillers, electric shock therapy, antidepressants, anticonvulsants, and physiotherapy (flex the limb that isn’t there, etc.). Some anaesthetics and hormones, when used prior to amputation, can reduce the likelihood of pain developing, but once it occurs, the best approach will vary from person to person.

Fans of the TV show House M.D. may be familiar with another, extremely clever, treatment that was developed in the 1990’s which involves outsmarting a person’s own brain. The philosophy behind the so-called “mirror box therapy” is that if the brain can trick someone into feeling a limb that isn’t there, it might be possible to use the old double fake-out on a person’s brain and convince it that the limb has actually been there the whole time. The way it works is that you build a box without a ceiling and create two evenly spaced holes on one side of the box to put your limbs (one whole, and one less-than-whole) through. Then, place a mirror down the centre that splits the box into two with a hole for each compartment and the mirror facing the side on which the whole limb will go. When viewed at a certain angle, it looks like the less-than-whole limb is actually a whole one, due to the mirroring of the real whole limb. By visually tricking the brain into thinking the phantom limb is there, a person can learn to control it such that it diminishes or completely eliminates the painful sensations. The process takes times and there hasn’t been a whole lot of research into why it can work, but many patients report long-term improvements… though not as fast as the guy on House.