Study: Back Pain Linked to Brain Shrinkage
Neuroscientist Vania Apkarian of Northwestern University has been involved in a series of studies looking at the effect of chronic pain on brain size and density.
In one study, Apkarian’s team continued to study the brains of people with chronic pain, in this case 10 people with chronic back pain. The researchers measured gray matter in the brains of people with chronic back pain and compared them to a group of 20 people who did not have chronic pain.
After looking at average brain size across each group, he compared the pain subjects with subjects free of pain and found significant differences in brain density in the tissue in the brain that houses neurons, or nerve cells, that communicate with each other to help us process information. With age, we naturally lose some gray matter but Apkarian notes a difference when pain comes into play.
In another study Apkarian used magnetic resonance imaging (MRI) scans to collect 26 brain images from people who reported suffering back pain that lasted for a year or more and 26 images from pain-free subjects matched for age and sex.
The changes in people with chronic pain, Apkarian told Reuters Health in an interview, were particularly noticeable in parts of the gray matter that are known to be important in making "emotional assessments," including decision making and control of everyday social behavior.
"We have shown that brain chemistry is abnormal in chronic back pain patients," Apkarian said. He cautioned however, that "we have no idea" whether the shrinkage causes the back pain or vice-versa. The two phenomena could also be unrelated.
The measurements revealed that people with chronic pain had less gray matter — overall and in a part of the brain called the thalamus. Not only was there less gray matter in terms of volume in pain sufferers, but the tissue was also less dense, Apkarian said.
The research raises "a whole new set of questions" about chronic pain, Apkarian said. "This is just the beginning at looking into the brain at what chronic pain really is."
He would like to follow a group of people with chronic pain to see whether the changes in gray matter progress. If gray matter continued to shrink as the pain continued, it would support the idea that the shrinkage is caused by chronic pain, he said.
One question Apkarian would like to see answered is whether treating the pain can reverse the damage to the brain’s gray matter, although he said such a reversal is unlikely.
Apkarian noted that even though "a lot of work" needs to be done in studying the relationship between gray matter changes and chronic pain, the possibility that pain can cause parts of the brain to shrink highlights the importance of treating chronic pain.
The Journal of Neuroscience, November 17, 2004 • 24(46):10410 –10415
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