Phantom Limb Pain
Sometimes people who have lost a limb, or were born without a limb, experience all the sensations of having that limb. This experience is commonly referred to as having phantom limbs, and they have been recorded for over a century. One of the striking features about these Phantom Limbs is that people can experience very real pain from their phantoms. This raises a number of questions about how we experience pain and how we interpret sensory information
Melzack (1992) reviewed the evidence on Phantom Limbs and noted that they have the following remarkable features.
1. Phantom limbs have a vivid sensory quality and precise location in space - at first people sometimes try to walk on a phantom leg because it feels so real.
2. In most cases, a phantom arm will hang down at the side when the person sits or stands, but moves in co-ordination with other limbs when the person is walking.
3. Sometimes it gets stuck in an unusual position - for example, one person had a phantom arm bent behind them, and could not sleep on their back because the limb got in their way.
4. Wearing an artificial arm or leg enhances the phantom, and it often fills the extension like a hand fits a glove.
5. Phantoms have a wide Range of sensations including pressure, warmth, cold, dampness, itchiness and different kinds of pain (around 70% of amputees suffer pain in the phantom).
6. Patients perceive phantoms as an integral part of the body - even when a phantom foot is felt to be dangling in the air several inches below the stump and unconnected to the leg, it is still experienced as part of the body and moves accordingly.
7. Phantoms are also experienced by some people with spinal injuries and some paraplegics complain that their legs make continuous cycling movements producing painful fatigue, even though their actual legs are lying immobilised on the bed.
Melzack gives an explanation for these findings. He suggests that the Brain contains a neuromatrix - or network of neurones. This neuromatrix responds to information from the senses and also generates a characteristic pattern of impulses that indicate that the body is whole and is also your own. He calls this pattern the neurosignature. It is perhaps helpful to think of it as a mental hologram that builds up a picture of your body in the mind. If a limb is removed, the sensations cease from that region but the hologram is still created in the neuromatrix.
