A 7-part Series on Chronic Pain
by Josh Meyers, PT, DPT, OCS
Pain is good. It helps one to avoid danger, survive an injury, and protect oneself when confronted by physical or emotional threats. The problem arises, however, when pain persists after a danger is removed, an injury heals, or a threat is no longer present. Medical providers call this persistent type of pain chronic pain, and it is the leading cause of disability in America.
Hope, however, lies in the fact that chronic pain is treatable. Through this series, readers will learn how chronic pain develops, recognize common symptoms, and understand how chronic pain is treated. Our goal is to empower readers to take action and regain control of their pain. Comments at the end of each post are welcome. Be sure to ask questions and share experience to help others with similar symptoms.
Part 2: The Brain Decides
The last post explained how the body’s nervous system functions as an alarm system and how that system can contribute to chronic pain after an injury or traumatic experience. This post explains how the brain produces pain when the body’s alarm system is activated.
Most people understand that the alarm system activates when a person steps on a nail. What most don’t understand, however, is how this alarm system generates pain. Most would say that pain works like this; one steps on a nail, the foot generates pain, and “pain” nerves relay the message that the foot hurts. The problem with this explanation is that “pain” nerves don’t exist. Stop and think about that. If “pain” nerves don’t exist, how does one experience pain?
Eyes Don’t See, Ears Don’t Hear
Let’s start with a simple analogy. When it comes to vision, people do not “see” with their eyes. Eyes contain light receptors that convert light to electrical signals. The optic nerve carries these signals to the brain, and the visual cortex (the part of the brain that processes visual information) forms an image in the mind. The image a person “sees” is the brain’s interpretation of light input, not the actual image. This is why optical illusions work; the brain ultimately decides what to “see”. 1
In the same way, ears do not “hear”. Ears have vibration receptors that convert vibrations from the air into electrical signals. The auditory nerve carries these signals to the brain, and the auditory cortex (the part of the brain that processes auditory information) forms sound in the mind. What a person “hears” is the brain’s interpretation of auditory input, not the actual sound. Remember the “Yanny” vs. “Laurel” sound bite debate last year? The word one heard was an interpretation of the sound bite. Although both words sounded similar, the brain ultimately decided what to “hear”. 1
Is There a Threat?
Similar to sight and sound, the brain collects nerve input from the body and interprets the significance. This nerve input, or nociception, is information that nerves send to the brain about pressure, temperature, movement, or chemical irritation in tissue – not pain. Interestingly, nociception does not include relevance or importance of these signals, just the fact that they are present. Relevance and importance are left to the interpretation of the brain. As the brain interprets nociceptive input to assign relevance or importance, it considers the full context of the physical environment, beliefs about pain, past pain or injury, and the need for self-preservation. Pain generation is ultimately driven by the answer to one question, “Is there a threat?” 1,2,3
Levels of nociceptive input from nerves do not drive pain, interpretation of perceived threat does. If a person steps on a nail in a safe environment, the nail is the most threatening part of that environment. The brain will likely produce pain (in addition to the increased awareness of the nail in the foot) to notify the person that danger is present. However, if a bear is now chasing that same person when the foot hits the nail, the brain will likely delay a pain experience in order to give the person a chance to run to safety. Same person, same nail, but the presence of the bear causes the brain to interpret the situation differently. 1,2,3
Changes in Perception
For those with chronic pain, changes in interpretation of nociceptive input are the problem. Instead of delaying pain, however, these changes cause hypersensitivity and amplify pain. Movement that was once interpreted as “non-threatening” is now painful because the brain perceives it to be a threat. (“It always hurts when I move.”) Sensitivity to touch produces pain with pressure that once was benign. (“Even small amounts of pressure hurt me a lot.”) Changes in temperature now produce pain. (“My back hurts more when it is cold outside.”)
While chronic pain has a stigma of being a “permanent” condition, research has shown that that these changes with interpretation of “threat” can be reversed. Physical therapists routinely utilize activity, graded exposure, and pain education to desensitize a nervous system, retrain “threat” interpretation, and restore normal sensitivity thresholds in a person’s nervous system. The next post will discuss how these changes occur, but first…
Let’s Hear From You
What are your experiences with pain? Are you surprised that there are no “pain” nerves? Share your experience in the comments below.
If you suffer from chronic pain, there is hope. Call us today to find out how physical therapy can help treat your chronic pain.
- Louw A, Puentedura E. Therapeutic Neuroscience Education: Teaching patients about pain. Minneapolis, MN: OPTP; 2013.
- Moseley, G.L., A pain neuromatrix approach to patients with chronic pain. Man Ther, 2003. 8(3): p. 130-40.
- Melzack, R., Pain and the neuromatrix in the brain Journal of Dental Education, 2001. 65: p. 1378-1382.