"In what sense is it true, that my hand does not feel pain, but I, in my hand? How is it to be decided? ...if someone has a pain in his hand, then the hand does not say so (unless it writes it) and one does not comfort the hand, but the sufferer; one looks into his face." - Ludwig Wittgenstein1
Whether short or long-lived, the odds are you have had a memorable encounter with a patient experiencing pain or with your own experience with pain. As health care providers, we routinely look into the face of someone in pain.
So what is it that we are looking at? What is pain? Sounds like an easy question, however the answer will vary depending on who is asked.
Some are still honoring Descartes and will likely answer that pain is a warning signal that there is tissue damage. If that were true though, how do we explain pain-free major trauma? Another common answer is that pain is the body's way of telling its owner that something is wrong. If so, then how do we understand phantom limb pain? And some will answer that pain comes from flawed or "fragile" anatomy, in some never ending terrible sounding ways - i.e. your spine is "out", your disc has "slipped", etc. (Note: unless fractured, spines do not uncouple themselves "out" of place nor do discs ever slip, anywhere).
The current definition from the world of pain science is that "pain is a multiple system output activated by the brain based on perceived threat."2 Pain is no longer thought of as a measure of tissue damage, commonly referred to as the patho-anatomical or biomedical model of pain. Pain doesn't actually work that way.
Pain is a complex and sophisticated protective mechanism consisting in part of specialized nerves that detect potentially dangerous changes in temperature, chemical balance or pressure. And get ready to tear out several pages of your physiology books! We don't have "pain" receptors. We do, however, have specialized nerves that detect the threats previously mentioned. These threat-detectors are called nociceptors that send alerts, not pain signals, to the brain for assessment.
The experience of pain then is dependent on the brain’s evaluation of a massive amount of informational input, including intel from its threat detection system, other sensory input (vision, smell, etc.), and cognitive data (past pain experiences, previous exposure to others in pain, cultural norms, beliefs, expectations, mood, etc).
In summary, the brain receives inputs that it processes into a soup of current and previous inputs, and then creates an output. And pain is just one output that the brain might use as a protective homeostatic response.
Pain’s complexity makes it more challenging to treat, but it also means that some of its contributors are more manageable than others - but only if we have an understanding of how pain works. Check back next week to learn more about the context of pain.
- Wittgenstein, Ludwig. Philosophical Investigations. Oxford: Blackwell; 1953, #286.
- Moseley, G.L., A pain neuromatrix approach to patients with chronic pain. Man Ther. 2003; 8(3):130-40.