I first came across the idea of neural tension while at dinner with the late David Lamb, one of the original architects of manual therapy education in Canada . He asked me if I’d ever heard of the work of Alf Breig, a Swedish neurosurgeon who had written a book several years earlier about his experience using surgery to resolve neurogenic pain. Breig proposed that many chronically painful conditions were due to the presence of mechanical tension within the neural structures, not compression. As it turns out, he was right. This concept of dysfunction remains largely unknown to the vast majority of physicians and therapists currently involved in the management of chronic pain but the reasons for that are best left to another essay. Here I want to talk about the sort of creative leap Breig had made and how this sort of thinking often leads to true advancement in science.
Deduction and Induction
Like any detective, scientists reason in various ways in an effort to move closer to the truth. Any therapist allied to science as a discipline (in my experience, not all are) is probably familiar with the two classical forms of reasoning; deduction and induction. Deduction is a form of reasoning that makes specific predictions from general premises while induction goes in what might be called the opposite direction-it moves from particular facts to general statements. Knowing the tolerance of connective tissue to mechanical stress we can say that it will fail in certain ways-this is deduction. Seeing a pattern of callous formation on the hand we can safely assume that repetitive stress is placed upon the limb-this is induction.
Appropriate therapeutic intervention is dependent upon the use of both induction and deduction and I’m sure you can see this if you think about what you’re doing to the patient and why. I’m going to leave these two now and focus on a third less well known form of reasoning.
Abduction
The following section was inspired by Burton S. Guttman’s essay “The Real Method of Scientific Discovery” (Skeptical Inquirer January/February 2004).
In the early 80s a resident physician in Australia named Barry Marshall drank a vial of water containing about a billion helicobacter pylori (H. pylori) bacteria. He felt certain that this would lead to gastritis, and it did. He also felt that the subsequent ingestion of an antibiotic would establish a connection between peptic ulcers and infectious disease that had never before been seen and hardly considered. Marshall ’s theory has been proven correct; this doctor’s preliminary investigation establishing the presence of H. pylori in the work that involved both deduction and induction-preceded what is known as abduction or retroduction (these terms are synonymous but I prefer the former).
Abductive reasoning follows the following pattern:
Some phenomena P is observed.
P would be explicable if H were true.
Hence there is reason to think that H is true.
In other words, the scientist confronts puzzles that arise naturally during the course of their work, thinking about them in light of their intimate knowledge of the system and then they make a creative leap of the imagination to say, “This would all make sense if H were true.” I find it interesting that this sort of reasoning is both very familiar and entirely absent from the various discussions about evidence based
practice.
I imagine Marshall saying, “If peptic ulcers are the result of an infectious disease process and H. pylori is the bacteria involved then a specific antibiotic would resolve the problem.” He proceeded to act upon that insight and moved the practice of gastroenterology in a direction it had resisted for many years. Marshall assumed that two things were connected that had not before been considered related, and his experiment consisting of creating an infection in his own system with the ingestion of bacteria (rather than with stress induced acidity). He then treated it successfully. This is an act of abduction and requires the investigator to imagine the world in a new way, thus the creative quality of the process. Like any creative act, it also requires some courage. Coincidentally, abduction is defined in the medical dictionary as “a movement away from the median.” Abductive reasoning invariably moves us away from the norm.
Abduction and Neurogenic Pain-The Problem of “Like Goes With Like”
The patient says, “I know it’s the muscle because I can feel it.” Those of us familiar with abnormal neurodynamics know full well that this complaint is due to a nervous irritation and that the muscular nociceptors aren’t significantly involved. We also know that our efforts to change this thinking and get the patient to understand and pursue treatment designed to restore normal neurodynamics may prove rather difficult. This isn’t because our idea isn’t plausible or too complicated. It’s just new, and because the meme of muscular pain is fighting for space in the patient’s brain and is already entrenched there, there’s no guarantee that our idea will win this battle. It may help to throw all of our authority and clinical skills into the fray, but success is never assured.
The root of this problem is explained by Gilovich and Savitsky in a brilliant article titled “Like Goes With Like: The Role of Representativeness in Erroneous and Pseudoscientific Beliefs” (Skeptical Inquirer March/April 1996). The authors describe the use of heuristics, “judgmental shortcuts that generally get us where we need to go-and quickly-but at the cost of occasionally sending us off course” to make connections that appear logical but are untrue. (See “The Fatal Heuristic” elsewhere on this site. Also, read the book “Blink:The Power of Thinking Without Thinking” by Malcolm Gladwell) They use the supposed similarity between the sensation produced by stress in the gut and that produced by a peptic ulcer as an example of a heuristic that led physicians to believe that stomach acid produced ulcers. They were wrong of course, but the doctor’s personal, visceral experience hooked that meme powerfully into their consciousness and dislodging it in favor of Marshall ’s alternative explanation became an enormous
task.
Similarly, the traditional ideas concerning the presence of “musculoskeletal” pain and the role of the contractile tissue as weak or short or lengthened or injured or in spasm or palpably sore is entrenched and encouraged by many wonderful and effective clinicians. It’s been my experience that teaching an alternative to this thinking that includes the latest studies in neurobiology has little effect on their theory or practice. Acceptance of the concept of abnormal neurodynamics as the primary reason for chronic discomfort requires that therapists shift the meme of muscular pain from its central role, and this will be allowed only after a major battle; a battle the idea of abnormal neurodynamics may not win.
So how did Breig do it? And, how did those of us who have revised our thinking about chronic pain relinquish the memes imbedded in our brains concerning the traditional attitudes about musculoskeletal pain and replace them with the concepts of neurodynamics and the consequences of its abnormality? I’m proposing that we have engaged in abduction. We have listened to countless patients describe sensations that cannot be explained using the paradigm offered us in school and one day said instead, “If abnormal neurodynamics were present that would account for the patient’s complaint-it would explain their story in a way that doesn’t violate what we now know to be true about the nervous system.”
This sort of reasoning is neither common nor easily done. It requires study, creativity and, most of all,
courage.
Do it anyway.