When people have similar injuries, why do some recover while others end up with chronic pain? New research published in Nature Neuroscience offers an intriguing theory: How your brain communicates following an injury may affect how your body feels.
What was the pain experiment?
Scientists from Northwestern University recruited 39 people with recent back pain and tracked their brain activity and pain levels over the course of a year. Brain scans were taken at four different points, including at the beginning of the study and close to the one-year mark. This novel approach differed from past experiments that relied on scans from just a single point in time.
What did the brain scans show?
At the end of the year, 20 patients had recovered, while 19 continued to hurtindicating chronic pain. By comparing brain scans, researchers were able to predict, with 85 percent accuracy, who went go on to develop chronic pain. The greater the interaction between two areas of the brain involved in emotion and motivation, the prefrontal cortex and the nucleus accumbens, the higher the chances of chronic pain. The researchers also noticed that participants who developed chronic pain lost gray matter early on in certain areas of the brain.
Why are these findings important?
"For the first time we can explain why people who may have the exact same initial pain either go on to recover or develop chronic pain," said A. Vania Apakarian, the study’s lead researcher and professor of physiology at Northwestern University’s Feinberg School of Medicine, according to a news release. "The injury by itself is not enough to explain the ongoing pain. It has to do with the injury combined with the state of the brain."
The more emotionally the brain reacts to the initial injury, the more likely the pain will persist after the injury has healed. "It may be that these sections of the brain are more excited to begin with in certain individuals, or there may be genetic and environmental influences that predispose these brain regions to interact at an excitable level," Apkarian said.
The nucleus accumbens is an important center for teaching the rest of the brain how to evaluate and react to the outside world, Apkarian noted, and this brain region may use the pain signal to teach the rest of the brain to develop chronic pain.
How might these findings one day contribute to new pain treatments?
If future studies confirm the brain's role in chronic pain, new drugs and therapies might be developed to reduce the troublesome communication. Such targeted treatments would be a boon to all who want to see an end to chronic pain.
"These results point to specific brain circuitry and biochemistry [for investigation]. Based on these results we will pursue novel therapy approaches," says Apkarian. "We hope that the search…will also identify means of treating chronic pain [in people who already live with it]."
News release, Northwestern University, July 1, 2012.
A. Vania Apkarian, PhD, Professor of Physiology, Northwestern University, Feinberg School of Medicine
Apkarian, V. et al. “Corticostriatal functional connectivity predicts transition to chronic back pain.” Nature Neuroscience, published online July 2012.