Losing a limb is a traumatic event in and of itself, but what if that limb haunted you for the rest your life?
In the sensory cortex of the brain, there is a map of the body. Each body part has its own designation in the brain where signals are sent when that particular body part experiences something sensory.
Consider that time you were walking through your living room barefoot and stepped on a Lego. Worst pain ever, right? Those signals travel at unthinkable speeds through your nerves, up the spinal cord, where they bounce around from various parts of your brain until they hit the “foot” region of the somatosensory map.
The more the touch receptors in the skin, the bigger the area allotted in the brain. These sections of the brain cross over each other, but usually don’t intersect. This very part of the brain is how you can tell what you’re touching, how painful something is, or even your orientation in space.
However, your brain can be fooled. Optical illusions can prove that. But what about physical illusions?
Amputee patients commonly experience a phenomenon called “phantom limb.” Basically, they can still feel, touch, and gesture (or feel like they’re gesturing) with an amputated limb. When told to grasp a mug, a patient with an amputated forearm was able to feel the mug underneath is missing fingers.  This particular patient, described in a Discover Magazine article, had lost the lower half of his right arm in a boating accident. Because he was a tennis player, he was able to switch to his left arm to play, but had trouble serving because “his ghostly right arm insists on holding the racket, too.”
When a limb, say an arm, is removed, the areas in the brain dedicated to that arm no longer get neural signals. But your brain doesn’t abandon that arm all together. In fact, the brain doesn’t even realize it’s missing after a while. This is because the areas around the “arm” region, in this case the “face” region, just spread out to encompass both regions. So when neurologist Vilayanur Subramanian was testing this theory, he touched amputee patients’ faces with a Q-tip, and they reported feeling the touch on their missing fingers. When he accidentally spilled a drop of water down the collar of one of the patients, the patient reported he felt water pouring down his arm.
Sometimes the patients feel unquenchable itchiness on their missing limb, or unbearable pain. Unfortunately, these discomforts can rarely be relieved because in the case, it really is all in their mind.
Part of the reasons these issues arise is because the brain has a hard time reconciling visual data with sensory data. While the map on your brain clearly has an arm on it, your eyes are seeing something much different. An original hypothesis was that the severed nerves at the end of an amputee’s stump just continuously sent pain signals to the brain, but removing the ends of those nerves didn’t help any.
I’ve read differing opinions on treatments or possible cures for phantom pain. If you watch House, MD, you’re probably remembering that episode where House cures his grouchy old neighbor’s phantom pain by placing his healthy arm in front of a mirror. While this is incredibly exaggerated (as many things on House are) there is still some truth to the treatment. Research suggests that you can fool your brain into thinking everything is normal with mirror therapy. Since your brain is only getting signals that scream CATASTROPHE! from a stump, some neurologists believe you can relieve the pain by putting the other, complete limb in front of a mirror to trick you brain into thinking everything’s dandy.
However, other research suggests that is complete bs, and it’s not that simple.
Neurologists aren’t even completely certain what causes the phantom limb phenomenon, or even how to help those patients who do suffer from it. Patients will just have to live with the ghosts in their brain for a little while longer.