Why Do Amputees Have Phantom Limb Pain?

Growing up, we had a family friend who had lost a leg. He lost the limb in an accident. From time to time he had terrible pains from the missing leg. How could this happen? Let’s take a look at how people experience pain and see if we can understand this better.

Pain is a weird thing. Why did evolution equip us with the ability to sense pain? If you think about it, it makes perfect sense. An organism that can feel pain would learn to avoid certain things in the environment that could hurt it. Organisms that could not feel pain would be more likely to get themselves hurt. So, once the pain adaptation arrived, those organisms that had it would be more likely to stay alive and pass on the adaption. Here is a good example. Say, you forget that one of the burners on the stove is on and you put your hand on it. What do you do? You withdraw your hand quickly and probably yell (I can only guess what you might say lol). If you didn’t feel the pain of the burner you would risk hurting yourself badly.

What do we know about how we sense pain? Your skin is the biggest organ your body has. There are free nerve endings near the surface of the skin which enable us to sense touch and temperature. These nerves endings are connected to the spinal cord which relays the sense information to the brain. The brain has an area in each parietal lobe that keeps track of touch sensations. This is called the somatosensory cortex. Sensation from the left side of the body is registered in the right somatosensory cortex and vice versa. So, the parietal lobes are wired for us to sense touch. If someone has an accident and loses a limb, the limb is missing but the nerve connections are still present in the brain. It is for this reason that people have phantom limb pains. All the connections are still present to register touch but the limb is gone.

Okay, so is there any way to treat this problem? The neurologist, V. S. Ramachandran has come up with a novel treatment. He devised a mirror box. He would have a patient who lost his hand put his hand in the mirror box. The patient would see the reflection of his hand in the mirror as though his missing hand were still there. Then Ramachandran would have the patient make a fist and extend his fingers over and over with his good hand. The reflection in the mirror would look like the missing hand was doing the exercises, too. After enough practice, the brain gets faked out and thinks the missing hand is still there. Patients who have used the mirror box report decreased phantom limb pain. I haven’t heard that the mirror box has been used with people who lost an entire arm or leg, but if you had a large enough mirror it would probably work, too.