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Certain signals in the brain may be connected to chronic pain. Blasius Erlinger/Getty Images
  • Scientists are examining signs from two areas of the brain to better understand chronic pain.
  • In a new study, researchers say signs from two areas of the brain linked to acute pain were activated during bouts with chronic pain.
  • Experts say the new findings could help in the development of treatments for chronic pain.

For the first time, scientists have measured biomarkers and activity in areas of the brain related to chronic pain (i.e., pain lasting 3 months or greater), shedding new light on a condition that affects more than 50 million people in the United States.

Researchers used functional MRI machines to investigate whether two areas of the brain known to activate during the experience of acute pain — the anterior cingulate cortex (ACC) and the orbitofrontal cortex (OFC) — are also activated when experiencing chronic pain.

Scientists gathered data from four individuals, three with chronic pain caused by stroke and one with a phantom limb after a leg amputation. The subjects had electrodes implanted to record ACC and OFC activity during chronic pain episodes.

These measurements, combined with self-reporting of pain severity and type, allowed researchers to use machine learning to predict chronic pain episodes by looking at OFC activity.

Acute pain, on the other hand, seemed to trigger more ACC activity, a separate study by the research team suggested. That study was limited, however, and further research is required, the authors noted.

The findings were published in the journal Nature Neuroscience.

“When you think about it, pain is one of the most fundamental experiences an organism can have,” Dr. Prasad Shirvalkar, an associate professor of anesthesia and neurological surgery at the University of California San Francisco, and first author of the study, said in a press release. “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.”

Prior studies into chronic pain primarily relied on self-reporting.

Experts say adding the additional dimension of direct brain scans helps scientists get a fuller understanding of the nature of chronic pain.

“Self-reporting and quantitative measures, such as brain scans, offer different benefits and drawbacks,” Dr. Dung Trinh, the chief medical sfficer of Health Brain Clinic who was not involved in the study, told Medical News Today.

“Self-reporting relies on individuals describing their pain experiences, providing subjective information about pain intensity, quality, and emotional impact,” Trinh explained. “This approach allows for capturing the lived experience of pain and its effects on daily life. On the other hand, self-reports may be influenced by individual biases, variations in interpretation, and memory recall issues.”

“Quantitative measures, such as brain scans, provide objective data on brain activity associated with pain,” he continued. “They offer a more direct and physiological measure of pain processing. Combining self-reports with objective measures can provide a more comprehensive understanding,” he added.

“Having studied neuroscience since the mid-80s and treated people with all types of spinal cord and nerve injuries for 34 years, it is exceptionally clear that there is a central, brain-mediated aspect to chronic pain,” said Dr. Robert Masson, a neurosurgeon at the Masson Spine Institute who was not involved in the study.

“The sophisticated organization of the brain, both relative to its intrinsic structure, but also related to its fundamental capacity to ‘learn,’ its plasticity both lend itself to an ability to reduce or enhance chronic pain,” he told Medical News Today. “The complexity goes beyond the pain itself, and it borrows from emotional brain, anxiety triggers, fight or flight or ‘sympathetic’ responses and over time change in neurochemical environment.”

The new research is part of a broader effort from the National Institutes of Health’s (NIH) Brain Research Through Advancing Innovative Neurotechnologies (BRAIN) initiative and the Helping to End Addiction Long-term Initiative (HEAL) initiative, the latter aimed at reducing the use of opioids and other painkillers in chronic pain management.

“Medication is a very small and poorly targeted part of the treatment strategy,” Masson said. “Understanding the complex interaction and biological machine learning that the brain iterates will help create pathways, earlier in the nerve injury episodes, that will diminish the targeted plasticity towards best recovery and away from embellished chronic pain and chemical dependency.”

The research teams say these findings could help inform other studies within HEAL and BRAIN that are treating chronic pain using deep brain stimulation (DBS).

Identifying the correct activity biomarkers for chronic pain through MRI is the first step in being able to “tune” DBS in a way that might help people with chronic pain.

“Chronic pain is a significant problem globally, contributing to disability and reduced quality of life for millions of people,” Trinh said.

“Current treatments for chronic pain often have limitations, and there is a critical need for more effective and non-addictive options,” he added.