What is pain?
Have you ever thought about it? I ask many patients this question and most everyone tells me, “Um… well it hurts,” or, “it’s unpleasant,” or better yet, “Well, um… pain is…it’s painful?” In fact most people have trouble defining what pain is, without using the word pain or a similar word.
To many, pain is…just pain.
Many people think of pain as a basic concept, defined by an unpleasant sensation. When this definition is used, the treatment of pain becomes obvious: remove the source of unpleasantness, and the pain will go away. In certain situations this may work very well. For example, if you step on a thorn it will likely be painful, and if you pull the thorn out of your foot, your pain will probably go away. However, there are many examples when this definition pain does not adequately describe the experience, or provide a framework for proper treatment of pain.
Take the above scenario with the thorn. Imagine that your job requires you to be on your feet most of the time, and that several days after stepping on the thorn you contract a bacterial infection in the wound. The infection is successfully treated but you still have a great deal of pain in your foot. Every health professional you consult assures you that there is no further infection, and that your foot has fully healed. Yet you continue to experience severe pain that prevents you from doing your job, keeps you from sleeping at night, and frequently hinders your family and social life. In this situation, there is a persistent unpleasant sensation in the foot, but no clearly identifiable source or cause. This begs the question, is our previous definition of pain correct? The truth is:
Pain is a protective mechanism, generated in response to threat appraisal, in the brain.
Let’s break down some facts about this definition:
· Pain’s purpose is to protect you
· It is a response to threat
· Threats are appraised in the brain
· The brain generates the pain response when the threat is sufficient to warrant action
With this definition of pain, we are able to better understand what is actually occurring when we experience pain. Whether we are talking about acute pain (as in the first example of the thorn), or chronic pain (as in the second example) the process occurs in mostly the same manner. Let’s outline both scenarios with the thorn below, as they occur physiologically.
Scenario 1 (Step on thorn-pain-remove thorn-pain goes away)
Scenario 2 (Step on thorn-remove thorn-infection-infection treated-chronic pain)
In the first scenario, the thorn pierces the foot, and nociception is generated. It is important to recognize that nociception is not the same thing as a pain signal. In fact, there are no such things as pain signals. Nociception would be better defined as a danger signal, thus its purpose being to alert the brain of potential danger. Once the brain is aware of this danger, it performs threat appraisal. This involves multiple areas of the brain including memory, thought, sensory integration, and recognition of any other threats that may be present. If threat is perceived, the brain will generate pain, and will modify the intensity of this pain according to the level of threat. The brain generates pain as a part of a protective mechanism. In other words, the brain is motivating you to take action to survive. In the first scenario, once the thorn is removed, the brain is satisfied with the action taken and ceases pain generation.
In the second scenario, there are multiple sources of threat (thorn in the foot, infection) thus the threat appraisal is now increased. In this situation, even though the thorn has been removed, and the infection cured, the threat appraisal continues to generate a need for pain generation and protective response. To understand why this occurs it useful to take a closer look at the threat appraisal itself.
A typical threat appraisal in the brain may look something like this:
· Do we know where we are right now?
· Are we safe?
· Have we felt this before?
· Are there other threats to our system right now?
· How does this affect my ability to work or survive?
· Am I under stress?
· Does the injury seem bad?
There are certainly other questions and appraisals which may occur, but let’s use these to better understand the second scenario. Do we know where we are right now? We are in an area with thorns. Are we safe? No, there is danger in our foot, as well as infection. Have we felt this before? Yes, it was painful, and it caused damage to the skin of our foot. Infections give us fevers, and threaten our whole system. Are there any other threats to our system right now? Infection, danger in the foot. How does this affect my ability to work or survive? I must be on my feet all day at work, this damages my feet, this could be very harmful. Am I under stress? I have all my normal stresses of life (mortgage, work, family, etc.). Does the injury seem bad? Yes, the combination of blood, broken skin, and infection make me wonder if something very serious is wrong.
The combination of all these questions creates an enduring pain experience that is now no longer dependent on the presence of a physical threat. Even after the infection is cured, and the wounds are healed, the initial threats to occupation and perception of severity make it very possible for this pain to persist in the absence of any physical problem. While the first scenario also undergoes the same threat appraisal process, different levels of threat, and different perceptions greatly alter the pain experience.
All pain is in the brain.
However, this does not mean that it is not real. It also does not mean that it is a psychological problem. Threat appraisal often takes place without conscious awareness. While psychology and thought can affect threat appraisal they are only one piece of the puzzle.
This is the first post of many on pain. In subsequent posts we will discuss more in-depth different diagnoses and conditions that are associated with chronic neuropathic pain, as well as recognition of these conditions, and their treatment. Stay posted and also check out our corresponding videos.