AUTHOR: Allen MacNeill
SOURCE: Original essay
COMMENTARY: That's up to you...
As some long-time visitors may be aware, I have not been able to update this blog for a long time. While part of this has been due to the press of other business, much of it has been due to two health problems, both of which have at their core what C. S. Lewis referred to as “the problem of pain.” Late last fall, and continuing until after the turn of the year, I suffered from a kidney stone. Then, in mid-January, my wife’s stepmother died of emphysema, and we drove 1,200 miles to be present at her funeral in Michigan. It was a hellish drive, through wind-driven lake-effect snow all the way from Jamestown to Toledo. I gripped the wheel with white knuckles and hunched my shoulders like a linebacker all the way.
The next day I awoke in agonizing pain, similar in quality to that produced by the passage of a kidney stone. But, unlike the kidney stone, the pain did not relent. It is still present, although finally it has begun to subside as the result of intensive physical therapy and the passage of time.
What kind of pain? Well, to be precise, it’s phantom pain. The cause (as far as anyone can figure out) is inflammation of the right lateral cervical nerve passing through a foramen between my sixth and seventh cervical vertebrae. To be precise, I have right lateral radial radiculopathy.
But that doesn’t describe what it feels like. Throughout most of the past two months it has felt like there is a cable of red-hot twisted steel running from the right side of the back of my neck, across the top of my shoulder and down the outside of my right arm to the middle three fingers of my right hand. This pain begins as soon as I wake up, and intensifies throughout the day until, after nightfall, it becomes overwhelming and the only thing I can do is take two oxycodone and lie down and wait for unconsciousness.
I describe all of this, not to elicit your sympathy, but to introduce “the problem of pain” from the standpoint of evolutionary biology. All of the rest of our senses have a physical referent: heat receptors sense heat, cold receptors cold, taste receptors sugars and ions and acids and bases and certain amino acids in our food, rods and cones sense the presence of light photons, etc. But pain receptors do not sense the presence of “pain.” No, “pain” is an “artificial sensation.” What pain receptors are adapted to sensing is cellular damage.
Why does pain exist? From an evolutionary standpoint, pain is “good for us”: in the past, those individuals who could feel pain would stop doing whatever it was they were doing that was causing the cellular damage that was triggering the pain, and therefore survived and reproduced more often than other individuals who did not feel pain so acutely. To be specific, individuals who had the cellular machinery to transform the chemical signs of cellular damage into action potentials in pain dendrites, and whose pain dendrites are connected to their central nervous systems in such a way as to cause changes in their behavior in such a way as to reduce such damage (and therefore reduce the amount of pain such damage causes) passed on to their offspring the genetic and developmental programs that produced the cellular machinery that made such responses possible.
But the problem with pain is that it doesn’t necessarily happen only when avoidable cellular damage is happening as the result of something we are doing. This is most obvious in the case of the two sources of pain that have crippled me for the past few months.
Kidney stone pain is widely recognized as one of the most intense forms of pain that we can experience. I know several women who have had babies and kidney stones, and they all assert that kidney stone pain is much, much worse. I know a couple of men who have had massive heart attacks and kidney stones, and they assert that kidney stone pain is worse (yes, the terror of having a heart attack is horrific as well, but terror is not pain, although the two are evolutionarily related). I have myself suffered various injuries, from chopping a wedge out of my shin with a macheté to breaking a bone to rather serious burns (especially on my fingertips) and none of them comes close to the pain of passing a kidney stone.
Yet, two questions immediately present themselves: why should passing a kidney stone produce pain at all, and why is the pain so intense? It is only via modern medicine that we understand what causes kidney stones; the most common cause is a familial tendency to produce very concentrated urine, combined with a genetically inherited defect in a couple of enzymes that in most people prevent the precipitation of calcium oxalate and/or uric acid crystals in the lumen of the pelvis of the kidney. Furthermore, the behavioral and chemical events that predispose one to forming kidney stones are so “detached” from the process of passing a kidney stone that they almost certainly cannot cause a person to stop doing whatever it was that resulted in the formation of the stones themselves.
Also, it is a general principle of the evolution of sensory systems that if damage to a particular tissue is virtually universally fatal, no pain receptors are present in that tissue. For example, there are no pain receptors in brain tissue; as my friend Will Provine can attest, people can probe around in your exposed brain tissue without causing the slightest amount of pain (he was fully conscious during the surgery in which his brain tumor was removed). You can literally stick an ice pick into a human brain and swish it around, and although it will cause massive neurological deficits, it will not cause any pain (this is how “ice pick” lobotomies used to be performed, generally without anaesthesia).
So why are there so many exquisitely sensitive pain receptors in the lining of our ureters? It would seem to me that damage to something as deeply embedded in the body as a ureter would almost certainly be fatal, and so why are there pain receptors in them? And why is the pain so extravagantly severe?
One possibility is that the pain receptors are there because people who did not have them would contort or twist their bodies so much during vigorous or violent activity that they might rupture or tear their ureters, resulting in their death. However, that doesn’t explain why a kidney stone the size of a grain of sand should cause so much pain passing down a ureter with the inside diameter of a pencil lead.
And so on to my cervical radiculopathy. In the case of my right arm pain (which at times has been nearly as bad as passing a kidney stone), there isn’t any damage happening in my arm at all. Rather, the pain is the result of physical stimulation of the pain fibers in the seventh cervical nerve as it passes through the foramen between the vertebrae. That is, there is absolutely no connection between anything I am doing (or have done) with my right arm that has caused cellular damage in my arm, which has then been transformed into action potentials in the pain dendrites going to my central nervous system.
That this is the case is encapsulated in the term “radiculopathy.” What is causing the pain is cellular damage in the “root” (or “radicle”) of the seventh cervical nerve, rather than cellular damage in my right arm. In the beginning stages, this damage was so severe that I also had fasciculations in my arm, shoulder, pectorals, rhomboid, and trapezious muscles. That is, these muscles twitched and contracted spasmotically and uncontrollably, as “phantom” nerve impulses generated in the inflamed motor neurons of the seventh cervical nerve stimulated those muscles to contract.
And so I had both “phantom” pain and “phantom” muscle twitching, for months. Did any of this convince me that I should no longer drive out to Michigan with my hands clenched to the wheel and my shoulders hunched. You bet it did, but that can’t possibly explain how generations of my ancestors could have evolved an anatomical or physiological arrangement that is so prone to such derangements. For, as it turns out, cervical radiculopathy is one of the two most common forms (the other being lumbar radiculopathy, or “low back pain”, which I – along with nearly all of you – have suffered from repeatedly).
Once again, is there any “reason” for all of this extravagant pain? C. S. Lewis, in The Problem of Pain
, used an analogy with sculpting stone: that each “blow” of the pain we all feel is what “hammers” us into shape as people. That is, God gives us the ability to experience pain as a means of making us better people.
Well, what about “meaningless” pain, such as that which we experience in the case of passing a kidney stone or suffering from cervical radiculopathy? Believe me, I honestly don’t think either of these has made me a “better” person. On the contrary, they have made me a more exhausted, more tentative, more fearful person. Every hint of the return of such pain makes me cringe, and so only if God wants me to be a more exhausted, more tentative, more fearful person who cringes at the slightest hint of a kidney stone or returning arm pain does such an explanation make sense.
What makes more sense to me is that such pain is an unintentional side effect of a system that is otherwise adaptive. In a world in which cellular damage is an ever-present possibility, pain receptors have clear adaptive value. And if, under certain conditions, they produce “unnecessary” pain, that’s the price we pay for being adaptive.
For moral reasons, I tend to favor the evolutionary explanation. That isn’t to say that one can’t use unnecessary pain; I have consciously tied the pain in my arm to an exercise and weight loss program, which seems to be working so far (although I worry about what will happen when and if the pain in my arm finally goes away). But this is the result of a conscious and deliberate process on my part, to harness what would otherwise be a completely meaningless affliction to something I would like to accomplish, but have had difficulty doing in the past. Maybe that’s what Lewis is really saying as well, although I suspect not.
So, does the experience of pain make us “better people?” Only if we make it so, and then it isn’t the pain that is doing it, but rather our own determination to do so, which isn’t “natural” in any way.
Here’s wishing you all a happy (and generally pain free) New Year!
Comments, criticisms, and suggestions are warmly welcomed!
Labels: evolution, kidney stones, neurobiology, neurophysiology, pain, radial radiculopathy