Phantom pain is the sensation of pain in a part of the body that no longer exists, which often occurs after the loss of a body part, usually in the course of an amputation. Phantom pain usually occurs after the removal of parts of the extremities, but in principle it can occur anywhere where an amputation is performed, for example after a breast removal.
Cause
For a long time it was assumed that the affected persons imagined the phantom pain, later it was assumed that changes in the remaining residual limb would cause this pain. However, it is now known that phantom pain in the brain is caused by a faulty activation of the pain system. Accordingly, phantom pain can be understood as a type of nerve pain.
The basis of the pain sensation is that the pain stimulus is passed on, processed by the brain and finally evaluated. This is also a reason why different stimuli are subjectively judged to be differently painful. On the one hand, the so-called “projected pain” plays a role in the development of phantom pain: A nerve cord is assigned to a certain supply area, so that the brain knows where the stimulus comes from when an impulse is transmitted via this nerve cord.
However, this system can be deceived, for example, if you strike your elbow, you often feel a tingling in your little finger. Therefore the brain “projects” this pain onto the little finger. On the other hand, the strong pain that occurs during and after the loss of a body part leads to changes in the brain.
The sensorimotor cortex is the area of the brain responsible for processing and evaluating sensations, including pain. Every part of the body is represented there, the size of the respective area depends on the amount of sensations coming from there. After the loss of a body part, this body part is further represented in the sensorimotor cortex.
However, this brain region is reorganized: although the brain region assigned to the removed body part no longer receives impulses from its original part, the area is increasingly activated from neighboring areas. The stronger this reorganization is, the stronger the phantom pain felt. A further factor influencing the strength of phantom pain is the intensity of pain prior to amputation of the body part.
Negative sensations, such as strong pain, are stored by the brain in the “pain memory“, changes occur in the brain and the brain can later recall this pain. This can also happen when the actual cause of pain is no longer there, for example after an amputation. It can then happen that the body’s own pain-inhibiting mechanisms are no longer active, but the brain feels exactly the same pain as before.