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Spontaneous Chronic Pain Predicted by Signatures in the Orbitofrontal Cortex, Small Study Finds
Using machine learning methods, researchers have identified biomarkers of chronic pain in a specific area of the brain in 4 patients. They published their findings in Nature Neuroscience.
Researchers believe their findings are a first step toward identifying brain activity patterns behind perceptions of pain that may one day lead to the development of therapies that can affect brain activity and relieve suffering.
“Functional MRI [magnetic resonance imaging] studies show that the anterior cingulate cortex (ACC) and orbitofrontal cortex (OFC) regions of the brain light up during acute pain experiments. We were interested to see whether these regions also played a role in how the brain processes chronic pain,” said lead author Prasad Shirvalkar, MD, PhD, associate professor of anesthesia and neurological surgery, University of California, San Francisco.
All 4 patients in the study had refractory chronic neuropathic pain. Specifically, 3 had post-stroke pain and 1 had phantom limb pain. Each patient had intracranial electrodes surgically implanted that targeted the ACC and OFC.
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Several times a day for months, participants answered questions about their pain, including its strength and type as well as its emotional impact. Patients then used a remote control device to initiate neural recordings to provide a snapshot of activity in the ACC and OFC at that moment. Machine learning tools eventually enabled researchers to successfully predict individual chronic pain severity scores with high sensitivity based on the participant’s neural activity in the OFC.
“Chronic pain decoding relied on sustained power changes from the OFC, which tended to differ from transient patterns of activity associated with acute, evoked pain states during a task,” they wrote. “Thus, intracranial OFC signals can be used to predict spontaneous, chronic pain state in patients.”
“When you think about it, pain is one of the most fundamental experiences an organism can have,” said Dr Shirvalkar. “Despite this, there is still so much we don’t understand about how pain works. By developing better tools to study and potentially affect pain responses in the brain, we hope to provide options to people living with chronic pain conditions.”
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