In the first study of its kind, researchers from Northwestern University have found that chronic back pain actually shrinks the brain by as much as 11%. Specifically, it shrinks the gray matter, which makes up the part of the brain responsible for memory and information processing.
It is well documented that chronic back pain negatively impacts quality of life and increases anxiety and depression, but it has been assumed that any brain changes revert to a normal state after the pain stops, researcher A. Vania Apkarian writes in the Nov. 23, 2004 issue of The Journal of Neuroscience.
Apkarian and colleagues compared 26 healthy volunteers with 26 patients who had chronic back pain in the lower region for more than a year. Some patients' pain radiated through the buttock, thigh, and leg -- a sign of sciatic nerve damage, or sciatica. The source of the pain was not considered.
MRI brain images and other sophisticated imaging tests, which measured gray matter size, were performed on all patients. After adjusting for age and gender factors, scientists found that, overall, chronic back pain patients lost about 5%-11% of gray matter a year -- about the same as 10 to 20 years or normal aging, the researchers say. Typically, normal aging results in only about 0.5% of gray matter loss each year, they add.
Those with chronic back pain with sciatica had the largest decrease in gray matter. In addition, the more years someone has chronic back pain, the more brain loss they suffered.
It's possible that some of the brain shrinkage occurs without substantial nerve cell loss, suggesting that certain medications could potentially help reverse tissue shrinkage, says Apkarian, in a news release.
What's Behind the Brain Shrinkage?
By definition, chronic back pain is a state of persistent pain sensation with associated negative mood and stress, says Apkarian. Therefore, one possible explanation for the decreased gray matter is that nerve cells are working overtime, he says.
The researchers hypothesize that as chronic back pain persists it may become more irreversible and less responsive to treatment due to these brain changes.