How manual therapy can retrain neural networks in chronic pain patients to address pain and the brain
PAIN IS PERCEIVED BY THE BRAIN, AND OVER TIME THE BRAIN OF A CHRONIC PAIN PATIENT CHANGES AND ADAPTS. It locks them into a troubling cycle of pain, fear of pain and movement avoidance.
When patients begin to avoid movement, their pain only increases, severely impacting their quality of life and preventing recovery. Successful treatment of chronic pain must involve first an understanding of how pain impacts the brain and how those changes can be reversed, helping patients unlearn fear-avoidance behaviors.
The good news is that research in this area has already begun. Our research study published recently in the Journal of Pain¹ demonstrated that spinal manipulation therapy (SMT) is one effective method of reversing maladaptive brain circuitry in chronic pain patients, specifically those suffering from chronic low-back pain (cLBP).
Where pain lives
The idea that pain “lives” in the brain is not a new one. According to the biopsychosocial model of pain, pain involves psychological, social, contextual and environmental factors in addition to factors that are biological. Prior research has shown that learning and memory processes are key determinants of chronic pain. Over time, these processes cause maladaptive neuroplastic structural and functional brain changes that initiate changes in pain perception.
In other words, the way we think about pain can cause a change in our actual experience of pain. For instance, research by Robert Edwards, PhD, associate professor of anesthesiology at Harvard School of Medicine, explored catastrophizing’s role in chronic pain.² Catastrophizing is a set of cognitions, emotions, attitudes and beliefs that can come in the form of ruminations, feelings of helplessness or pain magnification. He found that individuals with a tendency to catastrophize are also at higher risk for developing a chronic pain condition. What’s more, the highest catastrophizers among chronic pain patients were also least likely to benefit from pain interventions. Among this population, opioid misuse is elevated.
Edwards’s research used fMRI brain mapping to understand how this catastrophizing was impacting the brain of study participants. He found that those with high catastrophizing scores did indeed have disruptive patterns of brain connectivity to the painful stimulus. Specifically, catastrophizing seems to drive connectivity between networks that are responsible for processing somatosensory information. These networks are not normally connected.
Retraining via SMT
Similar to Edwards’s research, our study used functional MRI scans to understand how cLBP patients respond to SMT on a cortical level. While previous studies have explored the psychological mechanisms of fear-avoidance behavior in pain, less is known about the brain mechanisms involved in pain and fear of movement. Understanding these mechanisms is important, as they influence behavioral decisions guiding patients in avoiding movement that is potentially painful or perceived to be painful.
During the course of the study, a licensed DC performed a clinical evaluation of 15 cLBP patients and 15 healthy control (HC) subjects to understand the nature of their pain symptoms and determine the suitability and safety of manual therapy. Patients were also asked to perform a series of back-straining exercises (such as sit-ups, leg lifts and pelvic tilts) and non-back-straining exercises (such as arm lifts and flexion extension of the arms), rating their level of back pain after each repetition.
On a separate visit, the brain responses of study participants were mapped with fMRI while they watched video clips depicting back-straining or neutral physical exercises that they knew they would have to perform at the end of the visit. Data collected during the initial clinical evaluation guided the selection of videos for each participant. The videos were individually chosen to maximize the contrast between back-straining and neutral exercises and most reliably exacerbate the patients’ pain. After watching the videos, the subjects rated how much pain they expected from performing the exercise and how fearful they were of performing that exercise. On a third visit, the task was repeated after a session of grade 5 spinal manipulation (for both cLPB and HC groups) or grade 3 mobilization (cLBP only).
Our findings included:
Compared with HC subjects, cLBP patients reported higher levels of expected pain and fear of performing the observed exercises.
CLBP patients demonstrated significant neural activations while they viewed videos of back-straining exercises but no significant activations viewing neutral exercises. The HC group, in comparison, demonstrated no activation and even deactivation in some cases.
The neural activations observed in cLBP patients occurred in brain circuitry involved in salience, social cognition and mentalizing. The engagement of this circuitry was reduced after SMT, with a slight increase in results for manipulation versus mobilization.
After cLBP patients received SMT, their report of clinical pain decreased, as well as their reports of anticipated pain and fear of performing the back-straining exercises.
In other words, this research demonstrated that SMT reduces pain, as well as expectation of pain and fear-based movement, suggesting that SMT may reduce cognitive and affective-motivational aspects of fear-avoidance behavior, along with the reduction of the corresponding brain processes. It may accomplish this by exposing patients to nonharmful but forceful mobilization of the painful joint, disrupting the relationship among pain anticipation, fear and movement — somewhat reminiscent of exposure therapy.
Furthermore, while SMT can produce positive results for chronic pain patients on its own, it may also be effective in combination with psychological therapy, such as cognitive behavioral therapy. In another of Edwards’s studies,³ for instance, fibromyalgia patients received five weeks of yoga intervention and experienced a 25% reduction in catastrophizing. Acupuncture yielded a similar result, as did mindfulness meditation and manual therapy. The patients whose catastrophizing scores improved the most also experienced the greatest improvement in symptoms over the course of the treatment.
This research has implications for the opioid epidemic sweeping the nation, an epidemic that in part stems from a poor understanding, and thus underutilization, of the non-pharmacological management of pain. Pharmacological treatment on its own has limited effects on chronic pain, possibly because pharmaceuticals are unable to target the deeply-ingrained association between pain anticipation, fear, physical maneuvers and pain. Our research adds to the understanding of non-pharmacological pain management by manual therapy with the hopes that one day non-pharmacological treatment will be the starting point in the treatment pathway for patients with chronic pain.
NORMAN W. KETTNER, DC, DACBR, DCBCN, FICC, has been a professor and chair of the Department of Radiology at Logan University for nearly four decades. In addition to his training and expertise as a clinical radiologist, his research interests include advanced brain imaging techniques to explore the neural mechanisms underlying chronic pain and the brain’s responses to acupuncture and spinal manipulation.
REFERENCES
1 Brain Mechanisms of Anticipated Painful Movements and Their Modulation by Manual Therapy in Chronic Low Back Pain. Ellingsen DM, Napadow V, Protsenko E, Mawla I, Kowalski MH, Swensen D, O’Dwyer-Swensen D, Edwards RR, Kettner N, Loggia ML. J Pain. 2018 Nov; 19(11):1352-1365
2 What do you expect? Catastrophizing mediates associations between expectancies and pain-facilitatory processes. Carriere JS, Martel MO, Meints SM, Cornelius MC, Edwards RR. Eur J Pain. 2018 Dec 3. doi: 10.1002/ejp.1348. [Epub ahead of print]
3 The relationship between catastrophizing and altered pain sensitivity in patients with chronic low-back pain. Meints SM, Mawla I, Napadow V, Kong J, Gerber J, Chan ST, Wasan AD, Kaptchuk TJ, McDonnell C, Carriere J, Rosen B, Gollub RL, Edwards RR. Pain. 2018 Dec 7. doi: 10.1097/j.pain.0000000000001461. [Epub ahead of print]
