Any pain, especially if it is inadequately treated or persists over a long period of time, carries the risk of becoming chronic. This is caused by a change in nerve cells at the level of the spinal cord and brain. Learn more about chronic pain disorders.
Acute pain as a protective reflex
Everyone is familiar with pain, for example, after a cut on the finger or after a bruise. Pain was created by nature as a warning signal: When reaching for a hot stove top, free nerve endings pick up the pain stimuli and transport them in the form of electrical impulses to certain nerve cells in the spinal cord. There, acute pain triggers a protective reflex – the hand is removed from the hot stove top.
From the spinal cord, the stimulus is transmitted to the brain. This is where the actual pain processing takes place. In the thalamus the pain becomes conscious, in the limbic system the affective-emotional component is added, in the cerebral cortex the place of origin of the pain is recognized and the feeling is stored as an experience.
When the cause of the pain is removed, within a short time the information is presumably erased again. The pain has served its purpose, and the organism goes about its business.
Emergence of a pain memory
If the pain-processing nerve cells are exposed to strong stimuli over a long period of time, a pain memory may develop. That is, pain continues to be signaled to the brain even after the actual cause has long since been eliminated.
Eventually, the nerve cells involved become more sensitive and process even mild stimuli or touch as pain or pass on pain impulses without a cause.
A pain memory is not erasable
If pain chronification has already occurred, it is not currently possible to pharmacologically erase a pain memory that has developed.
So-called counterirritation procedures, such as transcutaneous electrical nerve stimulation (TENS) or electro-acupuncture, can in some cases reduce the increased sensitivity of the nervous system in the spinal cord.
Not all pain becomes chronic
Acute pain, especially if inadequately treated, can develop into excruciating chronic pain. But not all acute pain becomes chronic. This suggests endogenous factors that oppose chronification. Such antichronification factors have been little studied.