Reconnecting the Brain with the Body in Chronic Pain Research

Research into pain and the effect it has on the brain has been greatly informative over recent years, and has deepened our understanding of how chronic pain works. While we have gained greater insight into the role the nervous system plays in pain perception, gaps still remain in other areas of understanding. Such gaps include the connection between the central nervous system and peripheral tissue pathology, especially in relation to chronic musculoskeletal pain.

Integration of our current knowledge and findings is the aim of the game here. It is simpler to separate information into different categories and isolate single causes. But if that is all we do, we may fail to understand the body in its integrated, interconnected and complex nature.

A recent article published in the Journal of Pain has focused on the issue of “reconnecting the brain with the rest of the body in musculoskeletal pain research”, calling for a ‘whole of body and brain’ approach to understanding chronic pain. It’s a refreshing look at the pain problem, which was previously looked at the issue through different isolated lenses. This integrated approach that takes brain, body, psychosocial factors and more into consideration will likely be welcomed by chiropractors.

The paper starts by illustrating the way things are usually done when it comes to pain research. In the past, there has been a heavy emphasis on the structural approach from an orthopaedic angle. In recent years, however, there has been a shift toward the neuro-affective components of chronic musculoskeletal pain. Increasingly, research is seeking to understand the brain’s role when it comes to pain sensitisation, pain perception, and pain habituation. Similarly there has been a shift in clinical approach from a biomedical model to a biopsychosocial model, which considers mental and behavioral factors as well as just the biological aspects.

Science now recognises something called “the pain matrix” which includes aspects of chronic pain above the level of the actual “injury.” This pain matrix acknowledges that it is the brain and spinal cord that produce pain, not tissue damage in and of itself. Various parts of the nervous system act together to create it (in order to protect the body from further harm) [2]. The longer a person suffers pain in one area of their body, the more the brain becomes involved in their experience.

What did the recent research paper indicate?

The recent study appearing in the Journal of Pain stated that, “A challenge in understanding chronic musculoskeletal pain is that research is often siloed between neuroscience, physical therapy/rehabilitation, orthopaedics and rheumatology, which focus respectively on 1) neutrally mediated effects on pain processes, 2) behavior and muscle activity, 3) tissue structure and 4) inflammatory processes. Although these disciplines individually study important aspects of pain, there is a need for more cross-disciplinary research that can bridge between them [1].”

This shift in perspective is one that appears to fit neatly within the chiropractic paradigm. We often discuss how dysfunction can exist long before it rises to conscious awareness – that is, it can be subclinical and the person can even be asymptomatic. This dysfunction, called nociception (or aberrant signals from the body to the brain), builds up until the brain recognises it as pain. Thus, pain isn’t the best indicator of illness/wellness.

While the medical world may not necessarily reflect that language, certain medical realities do. For example, medical imaging is no longer recommended for the majority of patients with low back pain as many asymptomatic patients have bulged discs or herniation [1]. Thus aiming to just ‘fix the broken part’ is not the most successful approach to treatment. While we, in the world of chiropractic already understand the importance of having full range of motion and healthy motor control and movement, the study’s author did point out another four critical areas in the comprehensive discussion. The paper indicated that [1]:

• There is great interest in understanding how acute pain transitions to chronic pain. Repeated injury may contribute, and inflammation can sensitise nociceptive neurons; how does this contribute to that transition. Even after pain and inflammation has resolved, scarring and other factors can restrict movement, and these restrictions can accumulate over time. Basically, there are lots of things that can contribute to the transition from acute to chronic pain.
• “There is evidence that body movements influence muscle growth and regeneration as well as connective tissue remodelling. Importantly, the shape of our musculoskeletal tissues reflects the movements that we do, as well as those that we do not do, such that tissues become less mobile in the directions that are not moved habitually due to poor posture and/or sedentary lifestyle. [1]”

•  “Less well-studied techniques and exercises that address whole body posture and movement could be useful in helping patients become aware of, and correct, posture and movement habits that may underlie seemingly “unrelated” musculoskeletal pain in different parts of the body.”
• There is a need for research into conditions that are commonly comorbid with musculoskeletal pain and how different systems within the body interact and contribute/modulate pain.

We know that when looking at a system so complex and intricate as the human body and brain, there is no single experiment that can address all variables. This is why the cross-disciplinary research called for in this paper is crucial, and there is a lot left to be done. The papers author mentioned that, “Some interdisciplinary groups have been working at these interfaces with promising results. Physical therapy, which traditionally had focused on musculoskeletal function, is increasingly bridging to psychological behavior and neuroscience.” This paper essentially called out those knowledge gaps and highlighted the work that is being done to fill them, while calling for more breaking down of the siloes that research can so easily fall into.

How it links with chiropractic

On the surface, it might seem that there is a lot of work to do and a big shift to complete before we can start getting some answers. But here, in the world of chiropractic research, we are already watching some of this brilliance unfold in the hands of some of our professions brightest neuroscientists.

Chiropractic already takes a whole-of-person approach to care. We don’t treat symptoms. We check the spine and adjust subluxations, and see what the body does after that. The world of case reports constantly reveals a vast array of results (varying, of course, from person to person).

There have already been a number of peer-reviewed articles published by the team at the New Zealand College of Chiropractic and Haavik Research which show us that when we adjust the spine, we change the structure and function of the brain. Chiropractor and neuroscientist Dr Heidi Haavik is quoted as saying, “When we adjust dysfunctional segments or subluxations, we change the way the brain processes what’s going on in our bodies. Hence we are able to better process all that sensory information from through-out the body, and control the body in a better way.” She was commenting on a study examining two specific brain activity measurements (H reflex and V waves) published in the Journal of Experimental Brain Science [3].

Other papers included in this treasure trove of information include:

• A paper indicating that spinal manipulation of dysfunctional spinal joints affects sensorimotor integration in the pre-frontal cortex [4].
• A study indicating that spinal manipulation impacts pelvic floor control in pregnant women [5].
• A study indicating that spinal manipulation increases cortical drive to the limb muscles, and a further study indicating that spinal manipulation shortens the cortical silent period (which is essentially the gap between the brain impulse and the muscle response) [6,7].
• We also have studies indicating changes in muscle strength, endurance, cerebellar processing and a number of findings with regard to subclinical neck pain [8-11].

 

While all of these studies focus on brain function and how it responds to chiropractic care (i.e when we adjust the spine), it drop some breadcrumbs along the trail to understanding the intricate connections between brain and muscles.

Perhaps the most interesting piece of research on the topic of chiropractic care and pain emerged just last year [12]. It was a study examining central processing of tonic pain, and it covered the areas of pain sensitivity and pain habituation. The study took 15 subjects and measured their brains responses to pain when their hand was placed in a tub of ice. Some participants were given a sham adjustment and then the process was repeated. Others were given a true chiropractic adjustment. When it came to the chiropractic group, it showed that there was no pain habituation, and that their brain reacted exactly the way it did the first time they experienced that pain. While there is a lot of chiropractic specific research regarding the brain and body connection, this study is perhaps the one that most directly indicates that chiropractic may have a profound role in chronic pain.

While yes, the is a lot of work yet to be done, the indicators that chiropractic care can alter and improve the way the brain and body communicate, and more specifically the way the brain handles repeated pain experiences, is very encouraging.

We certainly can’t wait to see where it goes.

REFERENCES:

1. Langevin H, (2020), “Reconneting the Brain with the Rest of the Body in Musculoskeletal Pain Research,” Journal of Pain, https://doi.org/10.1016/j.jpain.2020.02.006
2. Staff Writer (2020) “What is the Neuromatrics of Pain?” Institute for Chronic Pain, https://www.instituteforchronicpain.org/understanding-chronic-pain/what-is-chronic-pain/neuromatrix-of-pain
3. Niazi I, Turker K, Flavel S, Kinget M, Duehr J and Haavik H (2015), “Changes in H-Reflex and V-waves following spinal manipulation,” Experimental Brain Sciences, 233, 1165-1173, https://link.springer.com/article/10.1007/s00221-014-4193-5
4. Lelic, D, Niazi, IK, Holt, K, Jochumsen, M, Dremstrup, K, Yielder, P, Murphy, B, Drewes, A and Haavik, H (2016), “Manipulation of dysfunctional spinal joints affects sensorimotor integration in the pre-frontal cortex: A brain source localization study,”Neural Plasticity, Volume 2016 (2016). 
5. Effect of Spinal Manipulation on Pelvic Floor Functional Changes in Pregnant and Nonpregnant Women: A Preliminary Study. Haavik, Heidi et al. Journal of Manipulative & Physiological Therapeutics , Volume 39 , Issue 5 , 339 – 347
6. Haavik H, Niazi IK, Jochumsen M, Sherwin D, Flavel S, Türker KS. (2017) Impact of spinal manipulation on cortical drive to upper and lower limb muscles. Brain Sciences. In Press
7. Haavik H, Niazi I, Jochumsen M, Ugincius P, Sebik O, Yilmaz G, Samran Navid M, Gorkem Ozyurt M and Turker K (2018), “Chiropractic spinal manipulation alters TMS induced I-wave excitability and shortens the cortical silent period,” Journal of Electromyography and Kinesiology, Volume 42 (2018), pp. 24-35
8. ] Daligadu J, Haavik H, Yielder P, Baarbe J, and Murphy B (2013), “Alterations in Cortical and Cerebellar Motor Processing in Subclinical Neck Pain Patients Following Spinal Manipulation,” JMPT Vol 36, Iss 8, October 2013 pp. 527-537, https://doi.org/10.1016/j.jmpt.2013.08.003
9. [5] Baarbe J, Holmes M, Murphy H, Haavik H, Murphy B (2016), “Influence of Subclinical Neck Pain on the Ability to Perform a Mental Rotation Task: A 4-week Longitudinal Study with a Healthy Control Group Comparison,” JMPT  39, Iss. 1, Jan 2016 pp. 23-30, https://doi.org/10.1016/j.jmpt.2015.12.002
10. [6] Haavik H, Ozyurt M, Niazi I, Holt K, Nedergaard R, Yilmaz G, Turker K (2018), “Chiropractic Manipulation Increases Maximal Bite Force in Healthy Individuals,” Brian Sciences, 2018, 8, 76; doi:10.3390/brainsci8050076
11. [7] Haavik-Taylor, H., Murphy, B., 2007a. Cervical spine manipulation alters sensorimotor integration: a somatosensory evoked potential study. Clin. Neurophysiol.: Off. J. Int. Feder. Clin. Neurophysiol. 118, 391–402.
12. Staff Writer (2019) “The Effect of Chiropractic Spinal Manipulation on Tonic Pain: Study Released” Australian Spinal Research Foundation, https://spinalresearch.com.au/the-effect-of-chiropractic-spinal-manipulation-on-tonic-pain-study-released/