Research

Research Advances Understanding of Brain’s Processing of Chronic Pain

Norman Kettner, DC (‘80), DACBR, FICC, dean of research and professor emeritus in the Department of Radiology, contributed to the study that found manual therapy (MT) both reduces chronic low back pain (cLBP) and modulates activity in cognitive, affective and sensorimotor areas of the brain that are important for the processing of pain.

The study, “Increased Salience Network Connectivity Following Manual Therapy is Associated with Reduced Pain in Chronic Low Back Pain Patients,” was published in the Journal of Pain in December 2020. It was part of a collaboration between Logan University, Athinoula A. Martinos Center for Biomedical Imaging, Oslo University Hospital, Melrose Family Chiropractic & Sports Injury Centre, Brigham and Women’s Hospital and Harvard Medical School.

“This paper is the most impactful and clinically relevant of my career, as it provides a new perspective for the underlying neurological mechanism of spinal manipulation in chronic low back pain,” Dr. Kettner said.

While cLBP has been associated with changes in brain plasticity, and non-pharmacological therapies like MT have shown promise for relieving cLBP, Dr. Kettner and the research team recognized the need for additional neuroimaging studies to understand the central mechanisms supporting MT. To investigate the effect of MT on resting-state salience network (SLN) connectivity and its potential association with changes in clinical pain, the team used functional magnetic resonance imaging (fMRI) to scan study participants before and immediately after two MT techniques: spinal manipulation and spinal mobilization. In addition to reducing cLBP through both manipulation and mobilization, the researchers observed MT significantly increased SLN connectivity to the thalamus and primary motor cortex.

“This study provides incontrovertible proof of the relationship between the brain and chronic pain as well as MT’s ability to alter the function of the brain in cLBP patients,” Dr. Kettner said.

This research builds upon findings from a 2018 study, “Brain Mechanisms of Anticipated Painful Movements and Their Modulation by Manual Therapy in Chronic Low Back Pain,” that Dr. Kettner contributed to that was also published in the Journal of Pain. The first fMRI study to examine mobilization versus manipulation in cLBP patients, it explored the link between fear and chronic pain. Its results suggest MT may reduce cognitive and affective-motivational aspects of fear-avoidance behavior along with corresponding brain processes.

“Many clinicians tend to neglect the influence of the brain by only examining the joint where patients say they are experiencing pain,” Dr. Kettner said. “Together, these studies show psychosocial influences have as much or more impact on chronic pain as biological ones, indicating a biopsychosocial model must be integrated into patient care for chronic pain and any persistent disorder.”

Dr. Kettner also noted both studies have important implications for the opioid epidemic in the United States. From 1999 to 2019, nearly 500,000 people died from overdoses involving opioids, according to the Centers for Disease Control and Prevention. “There are so many reasons to develop nonpharmacological pathways such as manual therapy for patient pain

Dr. Norman Kettner management,” Dr. Kettner said.

While there is a wealth of evidence that chronic pain alters brain structure and function, Dr. Kettner believes there is still a dearth of neuroimaging research to support the potential underlying central mechanisms of MT for cLBP.

“We still don’t understand exactly how mobilization and manipulation specifically alter brain activity,” Dr. Kettner said. “We only know that they do and where the brain activity occurs. We have many new directions to explore.”

Scan the QR codes below to read the 2020 study (left) and the 2018 study (right).

“Together, these studies show psychosocial influences have as much or more impact on chronic pain as biological ones, indicating a biopsychosocial model must be integrated into patient care for chronic pain and any persistent disorder.” – Dr. Norman Kettner