Chronic pain involves many complex physical as well as cognitive aspects, and can be hard to understand. Believe it or not, many of the predictors of who develops chronic back pain are not related to MRI findings but by the cognitive or “central” environment in which those physical findings are found. Many people then think, if my MRI is “normal,” then what is causing my pain? This confusion can cause more uncertainty, which increases a person’s cycle of pain, frustration, and immobility. Central sensitization (or amplification) of chronic pain is a real phenomenon that occurs but is a difficult concept for many to understand. We can explain it like this: your spinal cord has become exceptionally irritable and has “short-circuited.”
Instead of “filtering” normal pain signals, it instead incorrectly “amplifies” them. As peripheral pain signals are sent to the spinal cord, tiny cells determine whether the spinal cord nerve cells should to respond or not. For example, an itchy sensation, or even a sensation of having one’s sock fall down is typically filtered away from the spinal cord as “not critical.” This signal is normally desensitized. When a patient has an irritable spinal cord, even the weight of a bed sheet over their feet can cause extreme pain. When this occurs, we call it “central amplification” of the peripheral pain signal. A weak, stiff, or poorly contracting muscle’s signals can be amplified and then interpreted as pain.
It is important to understand that this central amplification process is not voluntary. You are not doing this yourself! If you were, we would just tell you to stop, and then your pain would completely disappear. Like a teacher whose ears are sensitized by rowdy children scraping their fingernails down a chalkboard, your spinal cord has amplified a particular peripheral pain signal so that it is interpreted as noxious and unbearable.