At some point or another, we all experience the sensation of pain. Pain is part of being a human and while it is unpleasant, it does give our bodies some useful information. It lets us know when we are injured and what our body’s limitations are. Sometimes though, after an injury, large or small, the pain just does not go away. It can, persist for months, and even for years. This type of pain is frustrating because no matter what you do, the pain just stays and eventually leads to functional impairments and disability. What can be even more frustrating is when you seek treatment for this pain, nothing seems to help. Even more frustrating is when the doctor orders tests and imaging (x-rays and MRIs) which do not show any tissue damage!
So what causes this type of pain when there is no more discernible injury? This is a question that has confounded the medical community for decades, but research done in recent years has shed some light on this phenomenon, which we are now calling Central Sensitization. To explain it, it helps to know a little of the anatomy and physiology involved in the sensation of pain.
All throughout the body we have nerve cells called nociceptors which measure excessive pressure, temperature, or other stimuli which could cause or suggest tissue damage such as inflammation. These nociceptors send electrical impulses up to your central nervous system (e.g. your brain) which then gets interpreted as pain. Specific areas of your brain that are activated include: your parietal lobes (where most of your sensory nerve cells are located), amygdala (a big connection area of your brain that impacts emotional responses such as fear), and hippocampus (another large connection area of your brain which helps with memory and other emotional responses). These areas activate so you know where the pain is, have an idea what may have caused it, and try to avoid doing the painful movement again. Normally, once the painful stimulus is removed, these areas deactivate and once any tissues that were damaged are healed, you do not feel pain anymore.
If you or someone you know are having problems with chronic pain, see your doctor for a Physical Therapy referral.
In Part 2 we’ll discuss how Central Sensitization plays its part in chronic pain and what one should do about it?