The size of a small area of the brain – mostly known for its role in decision-making – is giving scientists insight into risk for chronic pain.
Paul Geha, M.D., assistant professor in the Departments of Neuroscience, Neurology, and Psychiatry at the University of Rochester and fellow researchers used an MRI to look at the limbic system of the brain and found the size of the nucleus accumbens, a component of the system, can indicate if someone is at a greater risk of developing chronic pain.
The study, published in PNAS, followed 40 lower back-pain patients early in their recovery, and then followed up with them a year later. Some of those patients went on to develop chronic pain, while others recovered. And while every patient who became chronic experienced different levels of pain, an MRI taken a year earlier revealed these patients had something in common from the beginning – a smaller nucleus accumbens. “Measuring the volume of nucleus accumbens is a way to measure risk, not pain, but rather the risk a person has for chronic pain,” Geha said.
While the size of the nucleus accumbens did not change in people who developed chronic pain, brain activity in that area did. An MRI showed that patients with a smaller nucleus accumbens who developed chronic pain at the year mark lost slow frequency fluctuations. This provides evidence that lower nucleus accumbens volume confers risk for developing chronic pain and altered nucleus accumbens activity is a signature of the state of chronic pain. “In a sense, it is more like a pregnancy test, you have or don’t have chronic pain,” Geha said. A marker of the state of being in chronic pain that could be used as a diagnostic tool for these patients.
Predicting and measuring pain has always been a challenge for health care providers and patients. Geha believes this research could be a vital step to changing that. With more and larger studies he foresees these findings playing a significant role in helping providers determine if a person is at greater risk to develop chronic pain. Knowing this could change the course of treatment, follow-up care, and pain management. Geha points out this research is in line with previously published findings, which reinforce his findings. “Now you have something that is highly consistent across studies with brain imaging, which is very, very important. A biomarker’s reproducibility is something that, in general, imaging is trying to achieve and it’s hard,” Geha said.