What is Pain?


By Wil Forbis
July 1, 2015

The Our Wacky Brain collection:
Standard caveat: I'm not a doctor. My credentials in the fields of brains, pain and science are exactly zero. This article is simply food for thought for people interested in the subject. 

As usual with these wacky brain articles, I'm starting by biting off more than I can chew. Am I really going to offer a complete explanation of the mysterious sensation of pain, a torment that has plagued humans and other living creatures since the dawn of conscious species? Even a cursory review of the literature on the topic should make it clear that much of modern science is still vague about the subject. As this blurb on the work of pain researcher Fernando Cervero states...

...pain is the most common reason for people to seek medical attention, but...it remains a biological enigma. It is protective, but not always. Its effects are not only sensory but also emotional. There is no way to measure it objectively, no test that comes back positive for pain; the only way a medical professional can gauge pain is by listening to the patient’s description of it. 
However, there is a general model of pain that most people agree on and this is that pain is a kind of alert system for the body. If something is going wrong, if there is some structural damage, pain alerts us to tend to it. You reach out and touch a hot stove and retract your hand quickly as the burning sensation engulfs your nerves. (My first word as a child was "hot" after this very experience.) You break a bone in your body and the accompanying  swelling and throbbing is a sharp agony. You're attacked by a swarm of flesh eating ants and your body erupts in pain as the millions of tiny nibbles destroy the integrity of your flesh. 

You get the picture.

But the connection between pain and structural damage isn't always there. Some people feel fine and go into the doctor to discover they have a giant tumor growing inside them. Other people experience grievous wounds that cause blood to pour out of their bodies yet they don't feel much pain. Even more confusing are people who have a limb removed and continue to feel phantom pain in a part of their body that doesn't even exist! As a warning system, pain is not perfect, sometimes too quiet, sometimes too loud.

So what is pain?

It is worth taking a paragraph to discuss the basic mechanisms of how pain is felt in the body. As you likely know, your entire body is covered with sensory nerves that provide you with the sense we call touch. One particular type of these nerves is called a nociceptor. Different types of nociceptors fire up at different kinds of stimulus, primarily mechanical stimulus (like a piano falling on your leg), temperature stimulus (like a hot stove) and chemical stimulus (like acid.) Upon activation, these nerves send signals up the spinal cord and into the brain. The brain then interprets these signals as pain, similar to the way that it interprets the activation of light receptors in your eyes as a visual experience. To employ an oft-used phrase: the bane of pain is plainly in the brain.

I've certainly had my experiences with pain. As frequent readers know, I dealt with nagging chronic pain in my hands and arms for years. The first stabs of it occurred in the late 1990s when I became employed as a web developer and toiled over a computer keyboard all day (while playing guitar during much of my evenings.) The pain was then only in my right forearm; it came and went for years, slowly becoming harder to ignore. Eventually I tried to offload a lot of my typing and mousing chores to my left hand and it spread there as well.

The pain was never sharp or agonizing, but rather a constant dull-to-medium throb, like a fresh bruise*. (I don't mean to downplay it; it was enough to keep me awake many nights.) Somewhere around 2006 I sought treatment. My GP basically scratched his head, told me to wear an arm brace and prescribed a round of physical therapy. That helped a bit but it didn't last. Soon I was back in physical therapy several times a week. I took time off work and began exploring a variety of treatments including acupuncture, massage, trigger point therapy, hot and cold baths, changing posture, stretching (I used to stretch for an hour daily), a weird orthopedic neck traction device, electrical stimulation, epsom salt baths, Feldenkrais, inversion tables and probably a few more I'm forgetting. I ended having several M.R.I.s and nerve conduction tests that did or did not show abnormalities depending on the doctor who was looking at them.

* This sentence highlights a problem that plagues pain treatment and pain science: how do you describe pain? One person's medium pain might be another person's unending agony. Pain charts often use a one-to-ten pain scale, with level ten being something like "the worst pain you can imagine." But if I've never felt it how can I imagine it? The subjectivity of pain makes it a difficult devil.

During the course of this several year process, I ran out of money (I was only working part time, primarily by using voice dictation) and moved in with my Dad and his wife. My plan was to try and slowly heal by avoiding the activities that had damned me---computing and guitar playing---while regularly stretching and getting trigger point massages (which did seem to temporarily alleviate the symptoms.) And it worked for a while. But somewhere around 2011 I had a relapse. The pain slowly returned to its worst levels. I remember having a constant pain in both arms and thinking how intrusive it was. With that kind of pain, your mind can never truly wander away from it; it's always there. (I came to treasure that brief half-awake period in the morning when it feels like your nerves haven't fully "woken up" and sensation is diminished.)

I had, at this point, read a little bit of the work of Dr. John Sarno, a New York doctor who had seemingly cured back pain for many people (including celebrities like Howard Stern and John Stossel.) As I understood it, his view of chronic pain was radically different. Instead of being caused by a structural issue like a nerve compression, tight fascia or scar tissue, Sarno argued that much pain was caused by the mysterious entity we call the mind. He argued that by tending to the mind one could defeat his or her pain.

 
The Sarno Controversy
It should be noted that the Sarno approach is deeply rooted in the theories of Freud and thus controversial. What I mainly got out of Sarno and his fellows is that pain can have non-structural causes and can be treated with non-structural solutions. I leave it to others to vigorously debate the specifics of his ideas.
 

So I tried Sarno's approach* and, in a nutshell, it worked. It wasn't an overnight process as many of Sarno's success stories are. I read all of his books and several more by people advocating variations of his approach. (For those exploring the Sarno approach, I recommend his books plus Fred Amir's "Rapid Recovery From Back and Neck Pain",  Scott Brady's "Pain Free for Life" and the web site TMSwiki.) I did my best to quiet my mind, to reinterpret the experience of life in a less anxious way. I attempted some basics of meditation and, while I never got far with it, I feel it was beneficial. Mainly, I just took it easy. I would go to the park and take in the air and scenery. I went on long hikes and let my mind drift. The pain left in fits and starts; it would rescind, then return, then fade. Mostly what changed was my attitude towards the pain. It became less something to fear and more akin to an annoying child, a voice that could be tolerated with a certain bemusement.

* I should mention, none of the doctors, physical therapist or other members of the "official" medical establishment ever mentioned Sarno or anything like his approach. They were, at the time, thoroughly invested in structural explanations for pain. My sense is that this is beginning to change.

 

At the time I was a member of an Internet mail list called Sorehand, a discussion for people with, you got it, sore hands. I started to notice something about the people on the list who would report progress or cures. They were primarily the ones using techniques that calmed the nervous system: yoga, meditation and Sarno's ideas*. And so I started to rethink my ideas of what pain is and what caused it. I moved away from the structural "alert system" view taken by most doctors, physical therapists and so on, and more towards the idea that pain is complex and multi-faceted and interacts with our nervous system (which consists of the brain, spinal cord and nerves and could be said to be the biological correlate of the mind.) 

As I kept reading on the subject of pain, various anecdotes jumped out at me. It became clear that the structural abnormalities often found on M.R.I.s of patients didn't always correlate to actual pain. As the NY Times reported...

The problem, say researchers, is that back scans can turn up physical changes in the back that aren’t really causing any problem. One well known study from The New England Journal of Medicine put 98 people with no back pain into a magnetic resonance imaging scan. Even though all of them had healthy backs, two out of three of them came back with M.R.I. reports that showed disk problems.
Or, as this Times article on sports injuries stated .
Dr. James Andrews, a widely known sports medicine orthopedist in Gulf Breeze, Fla., wanted to test his suspicion that M.R.I.’s, the scans given to almost every injured athlete or casual exerciser, might be a bit misleading. So he scanned the shoulders of 31 perfectly healthy professional baseball pitchers. The pitchers were not injured and had no pain. But the M.R.I.’s found abnormal shoulder cartilage in 90 percent of them and abnormal rotator cuff tendons in 87 percent. “If you want an excuse to operate on a pitcher’s throwing shoulder, just get an M.R.I.,” Dr. Andrews says.
You may recall the following internet meme that circulated a few years ago. Wall Street Journal: Fake Knee Surgery as Good as Real Procedure, Study Finds.
A fake surgical procedure is just as good as real surgery at reducing pain and other symptoms in some patients suffering from torn knee cartilage, according to a new study that is likely to fuel debate over one of the most common orthopedic operations.

It was becoming clear to me that the structural view of pain, while doubtless correct in many (if not most cases) couldn't account for everything.

I also discovered that theories of pain that go outside the standard "alert system" model have been around for a while. One theory is Central Sensitization which basically argues that as you feel more pain, you get better at feeling pain and thus feel more pain leading to a horrible feedback loop. Another is the Gate-Control Theory that argues that stimulation of non-pain related nerves and brain areas can inhibit the activity of pain-focused nerves. (In a sense, you can distract yourself from the pain, shutting down the alert system.)

 

Beyond that, Australian pain researcher Lorimer Moseley has some interesting thoughts on how our conceptualization of the causes of pain can make us more vulnerable to pain. For example, many people fear the back pain that comes with a slipped disc. There's only one problem: slipped discs don't exist. Mosely posits a process by which thinking we have a slipped disc can make us more prone to back pain. (He uses the term "neurotag" to denote the specific network of cells that activate when a person is thinking about a certain idea or having a certain experience.)

If we have the phrase “slipped disc” in our brain... it has to be held by a network of brain cells (we can call this the “slipped disc” neurotag). And it’s highly likely that there are some brain cells that are members of both the slipped disc neurotag and the back pain neurotag. This means that if we activate the slipped disc neurotag, we slightly increase the likelihood of activating the back pain neurotag.

Using this model, thinking that we have a slipped disc has the potential to increase back pain. But what if this piece of knowledge we have stored is inaccurate, just like our notion of a slipped disc? A disc is so firmly attached to its vertebrae that it can never, ever slip. Despite this, we have the language, and the pictures to go with it, and both strongly suggest it can.

When the brain is using this inaccurate information to evaluate how much danger one’s back is in, we can predict with confidence that, if all other things were equal, thinking you have a slipped disc and picturing one of those horrible clinical models of a slipped disc will increase your back pain.

This struggle of conceptualization, this question of "what is causing my pain?”, was certainly something I wrestled with. An orthopedist would tell me one thing, a physical therapist would tell me another, a book I would read would offer a third answer. I remember having a certain sense of relief when one physical therapist confided to me that there was still a lot of mystery surrounding the topic of pain. I realized it wasn’t simply that I didn't "get it" or was being obstinate; pain IS a mystery. And this may be why Sarno's program works for so many people: it offers a explanation for pain that makes sense and  provides steps that can be taken to fix the problem. 

The vagaries of pain resonate with my general understanding of how the brain creates our sense of reality. We look out at the world, smell it, hear it, touch it, and think we are getting an exact representation of what's out there, yet we know that's not true. We know we only see a certain part of the light spectrum. We know we only sense some air vibrations as sound. We know that hallucinations and distortions of our senses are possible.  Pain, I imagine, is capable of being similarly distorted. It is likely we can have hallucinations of pain, sensory experiences that give the impression that something is there when in fact there is nothing.


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