MRI for lower back pain may be the poster child for overused imaging that offers little useful information. However, new research is flipping that notion on its head—literally—as functional MRI (fMRI) scanning has demonstrated abnormalities in brain structure predispose individuals to develop chronic pain after a lower back injury.
The study, published Sept. 16 in the journal Pain, could point to functional connectivity in the brain as a causal biomarker for pain chronification, according to Ali R. Mansour, MD, Northwestern University, Feinberg School of Medicine, Chicago, and colleagues.
“Our results indicate that white matter properties examined soon after initial pain onset robustly predict pain chronification one year later,” they wrote.
The longitudinal brain imaging study included 46 people who had a single episode of sub-acute back pain for at least four weeks, but had not experienced back pain in the preceding year. Patients had to rate their pain at least five out of 10 on a pain scale for inclusion in the study. Diffusion tensor imaging scans were taken at the onset of the study and at one year.
At follow-up, about half of the patients’ pain had improved regardless of whether the pain was treated. Those who had persistent pain also had white matter structural abnormalities at both the onset of the injury and at one year. In these patients, abnormal fractional anisotropy was identified in the nucleus accumbens and medial prefrontal cortex, which are regions involved with pain and emotion processing.
A second cohort validated the findings, and Mansour and colleagues reported that, based on the MRI scans, they could predict with about 85 percent accuracy which patients would have persistent pain.
“The abnormality makes them vulnerable and predisposes them to enhanced emotional learning that then amplifies the pain and makes it more emotionally significant,” Apkar Vania Apkarian, PhD, senior author of the study, explained in a press release.
The findings could change the way lower back pain is treated, with earlier, more aggressive treatment prescribed for those at risk for chronic pain.
Nearly 100 million people in the U.S. are affected by chronic pain, costing as much as $635 billion a year to treat.