A recent study led by researchers at Northwestern University Feinberg School of Medicine says it is now possible to predict within three days of whiplash injury, which patients will develop chronic pain, based on cross “talk” between regions of the brain and a person’s anxiety level after the injury.
The findings, published in in Nature Mental Health, were from a large-scale longitudinal look at whiplash patients to identify predictors of the transition from acute to chronic pain. The research—a collaboration between the Technion-Israel Institute of Technology, Northwestern University, and the McGill University—found that the more the hippocampus, the brain’s memory center, talked with the cortex, which aids in long-term memory storage, the more likely a person is to develop chronic pain. Also, the higher the anxiety level of the patient immediately after whiplash from a car accident, the more accurately the scientists could predict chronic pain people reported one year later.
The communication between the hippocampus and the cortex is thought to be indexing the formation of new memories related to the subjects’ accident and pain, said first author Paulo Branco, MD, assistant professor of anesthesiology and pain medicine at Northwestern University Feinberg School of Medicine.
While it remains unclear exactly why this heightened interaction between these two brain regions increases the risk for developing chronic pain, they theorize that the brain of the people who develop chronic pains has encoded a strong memory associating a head and neck movement with pain.
“This creates expectations and associations,” Branco said. “If the memory has high emotional significance, then it makes these patients associate this movement with pain. When the brain receives these signals, it pays more attention to them based on the painful memories that were formed by the accident.”
“While we commonly think of pain as relating only to an injury, it is the brain that actually makes up the pain experience,” he continued. “The brain makes the decision about whether a movement should be painful or not, and we think this may rely on previous experiences stored in memory.”
Senior author Apkar V. Apkarian, PhD, director of the Center for Translational Pain Research, said this research now points to a way for how to better treat whiplash patients.
“Now that we know there is this critical time period when this happens, we can focus our treatment efforts at this early stage to prevent chronic pain rather than try to cure it,” he said, noting that because patient anxiety plays a significant role in brain changes, that targeting patient anxiety as soon as possible after the initial injury with anti-anxiety drugs or other medications may stop these changes.
“Future novel treatments targeting hippocampal activity and connectivity through pharmacology or through neuromodulation techniques also are possible,” Apkarian added.
For their research, the investigators collected data from more than 200 whiplash patients between March 2016 and December 2021 and performed functional magnetic resonance imaging (fMRI) on patients within three days of their injuries, to assess brain activity in learning and memory regions. The patients were then monitored over the following year to track their pain levels. The data showed a clear link between early brain responses and long-term pain outcomes.
With this new understanding of the role the brain regions play in chronic pain development, the researchers will plan to further understand the underlying physiological and psychological mechanisms behind the hippocampus’s response to injury. The team also plans to expand their focus beyond whiplash injuries to determine if their findings are generalizable to other chronic pain conditions.
