A History of Pain Science

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History is not only about the study of the past, it can also be a lesson for the future. For example, NFL footballs team have won the Superbowl based on studying the film of the first half of the game in order to make adjustments in the second half. Politicians can deal with the economy  based on historical situations. The stock market has historical patterns of bull and bear market patterns that may help predict future trends.

How is learning the history of pain science important?

It is important to review the history of medicine and pain science to understand that what we know as truths can change with research. Have you heard in the past that eggs are not good for you? Then reports indicated that eggs were not as bad as we thought? You can find an argument for both sides. The same is true for pain science. We need to study the past as well as newer research to optimize our treatment to make sure we are practicing using proven methods and that we are not harming patients. As clinicians, we must be sure that the theories of treatment that we use are correct.

There are many theories involved with the treatment of pain. Unfortunately, some treatment theories have become part of a belief system which becomes very difficult to challenge and question. But we must! For clinicians viewing this website, please understand that treatment philosophies should not be based on beliefs, but should be based on sound research that we should freely be able to challenge and deconstruct. Additionally, we shouldn’t take it personal if someone disagrees with our explanations of treatment.

What I find interesting is that I often hear that many clinicians do things because their treatments work without trying to understand why it works. This can lead to problems. Here are some examples in general medicine:

In the past, one of the first treatments for fever was bloodletting, which is to simply let the person bleed. We now know that that bloodletting a person would reduce a fever because someone who is bleeding can go into shock and one sign of sock is cold clammy skin.

Heroin was regularly used in cough syrups and we now know that heroin is a very addictive drug.

Frontal lobotomies (removal of parts of the brain) were performed in the 1940s and 1950s for people with psychological disorders. We now know that destroying parts of the brain is detrimental to function.

Now diet pills are its own entity. There is no FDA regulation with diet pills, vitamins, and herbal remedies. How many diet pills have been on the market, and how many have been removed? How many are questionable? No one really knows except for the companies that manufactures them.

Now for pain science history:

One of the first pain theories involved Homer (8th century BC) who described pain as “arrows shot by Gods”. Aristotle (384 BC – 322 BC) stated that Pain was due to evil spirits and that the gods entered the body during injury. The brain was not believed to have any direct influence and for years the liver or heart was considered to be the center for pain control. Many cultures and societies have developed their own theories regarding pain, including causations from deities, energy fields, the moon, and the stars.

Rene Decartes (1596 – 1650),  the father of the Cartesian Model of Pain described pain as a stimulus created by the tissues as the origin of pain and the tissues send pain messages to the brain. The mind and the body were not considered to be connected to process pain. If you hit your foot with a 10 pound hammer, the brain will sense 10 pounds of pain. Based on the Cartesian Model, pain in the foot means that pain comes from the foot all the time. Examples of treatments that are based on the Cartesian Model of pain include epidurals, other types of nerve blocks, and cortisone injections.

We now know that this theory is not complete. If pain always originates from the body part that is injured, these treatments just mentioned should always work.  The lack of success is due in part because the Cartesian Model does not consider that pain can also be due to protective mechanisms, emotions, or sensitivity of the nervous system.

In 1965, Ronald Melzack and Patrick Wall (1925-2001) created the Gate Control Theory of Pain. They understood that the Cartesian Model of Pain was not complete so they created a new theory.  In this theory, the spinal cord is the gate that sends noxious messages  and non-noxious messages to the brain. (A noxious message is defined as a stimulus that is damaging or threatens damage to normal tissues. Remember that pain can increase due to actual or potential tissue damage. You can review the definition of pain here). If there is a noxious stimulus such as getting your knee hit by a 10 pound hammer, the brain will receive that stimulus. If you rub your knee, the spinal cord will receive this as a positive (non-noxious) stimulus, which will block some of the noxious stimulus that may be effecting pain. Another example of this is a child falling down and crying, when we kiss his or her knee, it feels better. Electrical stimulation or TENS units were created based on the Gate Theory of Pain. Pain may decrease while the stimulation was on, but would often return after the effects of the stimulation decreased.

Ronald Melzack knew that the Gate Control Theory was not complete because it does not explain various conditions including phantom limb pain. (WebMD has information about phantom limb pain here.)  How is it possible to experience pain in the leg even after it is amputated? One explanation involves the memory of pain that is stored in the brain. This memory can involve emotions, movements, even the time of year to trigger a painful response.

In 2001 Ronald Melzack described the Neuromatrix Model of Pain, which was updated together with Joel Katz in 2013. The Neuromatrix Model of Pain is an attempt to include all concepts of pain found in current research. Please check the the definition of pain and stories and metaphors sections to review what we discussed during your treatment. The neuromatrix model of pain is the most scientific and up to date explanation of pain. The stories and metaphors in a previous section is a way to use real life examples to help understand pain to take control of it. The Neuromatrix Model of Pain incorporates all of these concepts.

Here is a diagram of the Neuromatrix Model of Pain

The three items below play a role into the nervous system when there is an injury or potential injury.

1. Cognition: memories of past experiences, attention, meaning of pain, anxiety

2. Sensory System:  input into the body from the skin and within the body (joints, internal organs, etc)

3. Emotion: stress mechanisms,  blood pressure, and other automatic processes

The entire body consists of the pain neuromatrix, which is a “body-self matrix” that analyzes cognition, the sensory system and emotional components to create an output to parts of the brain to create pain perception, an action plan or pattern to respond to pain, and changes in stress regulation.

Lets use the same example that Lorimer Moseley uses in his book Painful Yarns that I shared in the Stories and Metaphors section.

The first time he felt a scratch on his leg, previous memories of getting his leg scratched were not significant. There was minimal cognitive attention  and anxiety or emotional connection to the scratch. Nerves on the skin sends the message of the scratch to the spinal cord then up to the brain. There was minimal pain because in prior experience, simple scratches are not significant injuries. There is minimal change in stress, blood pressure or other automatic processes.

The second time he felt that same exact scratch on his leg, the input to the brain triggered the memory of the previous incident and the meaning of the scratch is completely different. His brain associated the scratch with potential injury which can increase anxiety. There was increased stress, blood pressure and automatic processes to turn on protective mechanisms within the body. Pain is then created as an output of the brain with an action involving falling to the ground and taking a look at his ankle. There is increased stress response to force him to deal with the scratch.

So, by understanding that there are many components that contribute to the pain process, we can look at each possible factor. What this means is that the low back pain that many may experience for years may not be only due to a back problem, it may be more related to other components of the neuromatrix.

There are many in depth articles about the neuromatrix model of pain. Just do an online search. Here are a couple of sites in case you are interested in more reading:

Diane Jacobs, a physical therapist and educator practicing in Canada has written detailed explanations of the neuromatrix model on her blog.

Laurence Bradley, a professor of medicine at the University of Alabama has written an article about the neuromatrix model for the Journal of Rheumatology.

Joseph Brence a physical therapist and research has written about the neuromatrix model on his blog as well. He has won an award for best research blog for physical therapists in 2014!

What this means is that the body and the mind cannot be separated when treating a person experiencing pain. This can also be described as the Biopsychosical Model that was introduced by Dr. George Engel in the 1970s. You must give yourself the opportunity to treat or improve every aspect of the pain process. So ask yourself these questions:

Is your pain experience a direct result from an injury? yes it can be

Is your pain experience due to changes in the nervous system? Yes, without nerves, there would be no pain.

Is your pain modulated by brain (central nervous system)? yes, your brain creates an output of pain.

This does not mean the pain is in your head. It is real. Pain is always real, it is the mechanism of pain that researchers are slowly figuring out. So let’s be positive and continue movement exercises to give your body and brain the opportunity to change for the better.

Here is the most important question in this section: How does all of this information apply to you? If you experience pain in any part of your body, you now know that the pain can be influenced by an unlimited number of sources; it can be due to the injured site, the nerves, the brain, stress, worry, protective mechanisms and etc.

For clinicians reading this site, the reason your patient or client is experiencing pain may not be what you think. Also, the reason your patient improves following your treatment interventions may not be what you think. Just think about the bloodletting or frontal lobotomy examples. Those medical professionals were completely incorrect as to the reasoning for improvement of symptoms.

So if someone experiences knee pain, there are two main scenarios.

1. We tell them the problem is the knee. This can lead to catastrophization (stress and worry) that there is a problem with the knee which can lead to more pain.

2. We can educate our patients and clients that pain can increase due to the numerous possible factors that have the potential to improve. This may decrease catastrophization and promote a positive outcome. This is explained in the following sections and here is a preview:

Findings from X-rays, MRIs and CT scans will find problems in the body, but they do not tell you what is causing your pain.

Stress and worrying about pain can increase and magnify pain.

Pain can increase due to the trigger of the memory of pain.

As clinicians we must keep up the good work we are currently doing by helping our patients and clients understand and take control of their painful experiences to regain function. Let’s improve our explanatory model of why our patients improve to further enhance our patient’s progress.

I hope you enjoy reading the upcoming sections and please understand that your feedback is more than welcome.

References:

Engel GL. The need for a new medical model: a challenge for biomedicine. Science. 1977 Apr 8;196(4286):129-36. PubMed PMID: 847460

Forrest CB, Shi L, von Schrader S, Ng J. Managed care, primary care, and the patient-practitioner relationship. J Gen Intern Med. 2002 Apr;17(4):270-7.

Pettman E. A history of manipulative therapy. J Man Manip Ther. 2007;15(3):165-74. PubMed PMID: 19066664; PubMed Central PMCID: PMC2565620. Free full text

Woolf CR, Rosenberg A. The cough suppressant effect of heroin and codeine: a controlled clinical study. Can Med Assoc J. 1962 May 5;86:810-2. PubMed PMID: 14008278; PubMed Central PMCID: PMC1849153. Free full text

Braslow J. Therapeutic effectiveness and social context: the case of lobotomy in a California state hospital, 1947-1954. West J Med. 1999 May;170(5):293-6. Review. PubMed PMID: 10379224; PubMed Central PMCID: PMC1305592.Free full text

Lindau ST, Laumann EO, Levinson W, Waite LJ. Synthesis of scientific disciplines in pursuit of health: the Interactive Biopsychosocial Model. Perspect Biol Med. 2003 Summer;46(3 Suppl):S74-86. Review. PubMed PMID: 14563076; PubMed Central PMCID: PMC1201376. Free full text

Melzack R & Wall PD. Pain mechanisms: a new theory. Science. 1965 Nov 19;150(3699):971-9. Review. PubMed PMID: 5320816

Melzack R. Pain and the neuromatrix in the brain. J Dent Educ. 2001 Dec;65(12):1378-82. PubMed PMID: 11780656

Melzack R & Katz J. Pain. WIREs Cogn Sci 2013, 4:1–15.

Vetter TR, McGwin G Jr, Bridgewater CL, Madan-Swain A, Ascherman LI. Validation and clinical application of a biopsychosocial model of pain intensity and functional disability in patients with a pediatric chronic pain condition referred to a subspecialty clinic. Pain Res Treat. 2013;2013:143292. doi: 10.1155/2013/143292. Epub 2013 Oct 22. PubMed PMID: 24251035; PubMed Central PMCID: PMC3819919. Free full text

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