Back Pain Linked to Brain Shrinkage
Excerpt By Merritt McKinney, Reuters Health

NEW YORK (Reuters Health) - People with chronic back pain may experience shrinkage in the 'thinking' part of the brain, according to preliminary results of a small study presented this week at a meeting of the American Pain Society in Chicago.

The decrease in brain tissue remains a chicken-or-the-egg question for researchers, since they do not know which comes first -- the back pain or the shrinkage.

But if chronic pain turns out to cause parts of the brain to shrink, "the urgency to cure chronic pain becomes more important," according to Dr. A. Vania Apkarian at Northwestern University in Chicago, who heads the ongoing study.

In previous research, Apkarian and his colleagues uncovered evidence that people with chronic pain may experience changes in brain tissue called gray matter. Unlike white matter, which mainly holds the brain together, gray matter contains active "thinking cells" that are involved in processing information and memory. It makes up the largest proportion of the brain.

In the new 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.

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 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, he 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."

Right now, Apkarian and his colleagues are still recruiting people with chronic back pain, as they would eventually like to measure gray matter in 20 people with pain, he said.

The Chicago researcher said that 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.

Apkarian noted that in another study that has yet to be published, he and his colleagues found that people with chronic pain have "a very specific" type of decline in the ability to make emotional decisions.

Reference Source 89

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