Practical Science on Movement and Pain
Practical Science on Movement and Pain
If you want to understand how a complex system works, and you don’t have the design specs or the user’s manual, one way to get some insight is to engage in reverse engineering. This often involves breaking one part of the system and then seeing what happens. If you want to apply this technique to understanding the pain system, you can’t really just go and break people, but you can find people who are already broken and try to find out why.
That is why pain scientists are interested in the rare cases where the system appears to have gone totally haywire, such as congenital insensitivity to pain, allodynia, or phantom limb pain. These cases are a rich source of insight.
I recently read about a very bizarre example of pain system brokeness called pain asymbolia. I’m not sure what the takeaway is, but it is definitely thought provoking.
Pain asymbolia patients can feel pain and describe its quality and intensity. But they don’t consider it unpleasant, or feel very motivated to do anything about it! How can pain not be unpleasant? That sounds like a contradiction in terms. Like watching a Twilight movie, but it doesn’t suck. How can pain not hurt?
To understand pain asymbolia, it is useful to contrast it with congenital pain insensitivity. People with this condition were born without functioning nociceptors, and therefore do not receive any warning signals from their bodies at all. Their other sensory signaling is intact, so they can feel a knife cutting through their leg. They just don’t feel any associated pain. So in order to protect themselves from harm, they have to memorize the sensations that occur with tissue damage, and then take immediate action when they sense them. In other words, they have to create their own pain alarm system from scratch.
Pain asymbolia patients have functioning nociceptors, and can therefore experience pain in vivid detail. They can describe the location, intensity and character of a painful stimulus, whether it is strong or weak, burning, stinging, stabbing, etc. They just don’t consider the pain unpleasant and they are not motivated to avoid it. In fact, they may giggle or smile as the stimulus is being applied.
So it appears that pain is like a dish composed of separate ingredients. In pain asymbolia patients, for some reason the “ouchness” is missing. Like a cake that has no sugar, the whole point of the experience is lost. The technical explanation for this omission is that the “sensory-discriminative” dimension of pain is intact, while the “motivational-affective” dimension is missing. Apparently this dimension is provided by the insula and the parietal operculum, because pain asymbolic patients have almost invariably sustained brain damage in these areas.
What about the reverse problem – can we have the motivational-affective part of pain without the sensory- discriminative part? The sugar without the cake? In his book Feeling Pain and Being in Pain, Nicola Grahek discusses some examples that seem to qualify, such as one patient who could not locate or describe the character or intensity of pain caused by a precise laser to his hand. All he knew was that there was some vague undefined badness between his shoulder and hand that he wanted to avoid.
So is any of this knowledge relevant to people without brain damage? I think its useful to know that the unpleasantness of pain can be separate from its character or intensity. My personal experience is that the intensity of pain is in not identical to its unpleasantness. Of course there is a correlation, but there is often an observable disconnect.
For example, I find that I can tolerate a good degree of pain in my knee or foot without getting distracted, but even a slight disturbance in my neck or upper back drives me nuts, and gets all of my attention until the problem is solved. I recall one time when I had some sort of (thankfully temporary) illness that for some reason caused a huge amount of nervy pain to wander around all over my back for a few days. Although it certainly wasn’t any fun, there was definitely something about it that didn’t bother me as much as it should have. And it had a peculiar character as well, I almost felt that it didn’t belong to me, as if there was pain in the air and I just walked into it. Sometimes I would tell my wife: “Wow this really fucking hurts!”, in a voice that sounded more impressed than aggrieved. Of course I did a lot of whining as well.
My clients seem to have quite different attitudes towards pain. Some can go for years with nonstop serious pain and they don’t really seem very bothered by it or motivated to cure it. Dealing with pain is a just low priority in their life. The motivational aspect of pain isn’t as strong for them. Others will go to great lengths to deal with seemingly minor annoyances, such as tightness, asymmetry or just a vague sense of wrongness in certain areas.
I have noticed that some of my clients who suffer the most pain also seem to have the highest pain tolerance. I recall one client who hurt all over. I pressed at one point and said “I’m sorry does that hurt?” She was proud of being tough and said “you can’t hurt me.” I said “no you are incredibly easy to hurt. You just don’t care that much when you do.”
I wouldn’t call her a pain asymbolic, but perhaps we are all on a spectrum, where some of us have brains that tend to add less unpleasantness to the pain recipe than others. Perhaps learning to cope with pain involves developing some ability to modify the recipe.
What do you think? Have any good pain stories? Share in the comments.