December 16, 2020

How the brain is connected could unlock secrets to chronic pain

Neuroimaging analysis reveals difference in brain networks in patients with Fibromyalgia.

Neuroimaging of the Brain

Fibromyalgia affects nearly four million Americans. But trying to identify markers for the disorder — and for chronic pain in general — has been a difficult task. New research conducted through the University of Michigan’s Chronic Pain and Fatigue Research Center suggests the connections between different brain regions may play an important role in identifying chronic pain.

Using neuroimaging, researchers found that the organization of functional networks within the brain — that is, how different regions of the brain are more or less connected to each other — differed substantially in patients with fibromyalgia compared to a healthy control group. Fibromyalgia affects nearly four million Americans. But trying to identify markers for the disorder — and for chronic pain in general — has been a difficult task. New research conducted through the University of Michigan’s Chronic Pain and Fatigue Research Center suggests the connections between different brain regions may play an important role in identifying chronic pain.

Tony Larkin and Richard Harris, Ph.D.Tony Larkin, Ph.D. candidate, and Richard Harris, Ph.D.

Tony Larkin, a neuroscience Ph.D. candidate, led the study, which used fMRI data of at-rest fibromyalgia patients and a control group to map the organization of the brain. 

“We know that the brain is organized in a certain way, such that multiple regions of the brain are interconnected,” Larkin says. “We’re looking at the brain under the lens of a global network, where multiple brain regions are connected to one another into functional groups, or communities. Possibly, those connections could tell us something about how it works.”

Using normalized mutual information (NMI), researchers found that the brain network organization in chronic pain patients is more variable than in the control group. Furthermore, the brain regions typically involved in pain processing are differentially assigned to communities between patients with varying levels of clinical pain — the higher the clinical pain, the greater the variability. 

Larkin says pain research often focuses on certain regions of the brain thought to be associated with pain. With this study, though, researchers took a step back to look at the brain as a whole and the connectivity between multiple regions, simultaneously.

“The field is moving into a more integrative approach of the brain; there’s not just one brain region that is responsible for chronic pain,” he says, noting that researchers have previously used the network approach with schizophrenia and depression. “This analysis shows that the connections between two brain regions is highly important in understanding whether or not someone has pain.”

To that end, researchers found NMI accurately differentiated brain networks from fibromyalgia patients and healthy controls, suggesting that neuroimaging could improve diagnosis of the disorder and other conditions with underlying brain pathology.  

Senior author Richard Harris, Ph.D., says researchers are just now beginning to learn how chronic pain reorganizes the brain network as a whole.

“This study identified a novel brain marker that identifies chronic pain patients from healthy controls with 80 to 90 percent sensitivity and specificity, thus making this outcome potentially useful in clinical settings,” says Harris, the Center’s director of pain and fatigue neuroimaging.  

Larkin adds that the next questions are whether or not other chronic pain conditions also show altered network topology and whether or not this increased variability is really a marker of brain disease.

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Paper cited: “Altered network architecture of functional brain communities in chronic nociplastic pain,” NeuroImage. DOI:10.1016/j.neuroimage.2020.117504