After a concussion, many people say their whole body hurts, not just their head.
New research from the University of Arizona College of Medicine – Phoenix shows that a brain injury goes on to suppress the entire immune system, leaving patients more susceptible to infections, viruses and pain throughout the body.
In an article published May 13 in the scientific journal Molecular Pain, the Translational Neurotrauma Research Program reports that a brain injury can evolve into a disease condition, rather than being isolated to a single event. Furthermore, the disease process escapes the brain, to affect the entire body and its immune system.
Jonathan Lifshitz, PhD, director of the Translational Neurotrauma Research Program at Barrow Neurological Institute at Phoenix Children’s Hospital, in conjunction with the Department of Child Healthat the University of Arizona College of Medicine – Phoenix, led a collaborative team of scientists to the groundbreaking findings that Lifshitz called “both remarkable and simple.”
The group’s research showed that following a brain injury, the immune system is highly activated, so much so that immune-active molecules migrate from the brain to the body. New processes are initiated in the body that lead to peripheral sensitivity or pain in another part of the body.
In this study, rodents received brain surgery or a brain injury. Within a week after the injury, inflammation-promoting molecules were elevated in the brain and blood. These molecules were hypothesized to sensitize sensation in the paws of brain-injured animals and their response to a local inflammatory challenge (like a bee sting). Surprisingly, brain-injured animals that seemed to be recovered showed heightened sensitivity, which was exaggerated by the inflammatory challenge. The investigators showed that the activity of regulatory T-cells, which control activation of the immune system, were significantly reduced after brain-injury. Brain-injured animals did not regulate inflammation in the periphery, despite any direct intervention there.
“The study showed that the brain injury was challenging other systems in the body,” Lifshitz said. “The biggest complaint following a brain injury is neuropathic pain.”
Previous studies have shown that headache, hypersensitivity to light, sound or touch are complications of a traumatic brain injury. But the researchers said the innovation of their study was in examining pain in parts of the body remote to the brain injury. These outcomes were further exaggerated by introducing an inflammatory event.
The multi-disciplinary project was made possible by a network of collaborators. The primary experiments were carried out by Rachel K. Rowe, PhD, a Science Foundation Arizona Bisgrove Scholar at Phoenix Children’s Hospital. The five-year collaboration included experts in immunology and pain at the University of Kentucky College of Medicine. Francesc Marti, PhD, and Linda Van Eldik, PhD, guided experiments that showed dysfunction of the immune system following a concussion. Bradley Taylor, PhD, an expert in cellular pain mechanisms, helped design and interpret experiments that assessed pain in other parts of the body following brain injury.
Rowe and Lifshitz said the next step is to figure out how long it takes the body to recover on its own, and to study whether a therapeutic approach, such as T-cell injections, could help balance the immune system faster.