Fibromyalgia Support Group

Chronic Pain May Harm the Brain

February 6, 2008 — A new study indicates that chronic pain has a widespread impact on overall brain function, a finding that may offer a possible explanation for many of the common cognitive and behavioral comorbidities seen in such patients.

Using functional magnetic resonance imaging (fMRI), investigators at Northwestern University, in Chicago, Illinois, found individuals with chronic back pain (CBP) had alterations in the functional connectivity of their cortical regions — areas of the brain that are unrelated to pain — compared with healthy controls.

"This is the first clue we have that conditions such as depression, anxiety, sleep disturbances, and decision-making difficulties, which affect the quality of life of chronic pain patients as much as the pain itself, may be directly related to altered brain function as a result of chronic pain," principal investigator Dante Chialvo, MD, told Medscape Neurology & Neurosurgery.

The study is published in the February 6 issue of the Journal of Neuroscience.

According to Dr. Chialvo, previous research has shown that, at rest, the healthy brain is in a state of cooperative equilibrium, so that when 1 region is active, the others become less active or deactivated. The brain regions engaged in this resting state are known as the default mode network (DMN) and usually "shut off" when an individual is paying attention or undertaking a task.

However, the study found that compared with healthy controls, the regions of the DMN in chronic pain patients never "quiet down."

"Our paper shows pain not only hurts patients, but the unrelenting perception of pain also harms the brain. Using technology such as fMRI, we can objectively quantify this effect," said Dr. Chialvo.

Irreversible Changes?

For the study, investigators used fMRI to scan the brains of 15 patients — 7 women and 8 men — with CBP and compared them with a group of age- and sex-matched controls.

Study participants were required to complete a simple task, which involved tracking a moving bar on a computer screen while undergoing fMRI.

While the CBP group was able to complete the task as well as controls, Dr. Chialvo said, it was at the expense "of using their brain differently from the pain-free group."

Furthermore, the study suggests that, over time, chronic pain may lead to permanent reorganization of the brain. "We observed that the effect on the cortical regions was greater among individuals who had had chronic pain for a longer period of time."

If the study's findings are confirmed, he added, this may indicate a need for early, aggressive treatment of pain to mitigate discomfort and/or prevent associated conditions such as depression, sleep disturbances, and cognitive impairment.

Dr. Chialvo's next research steps will include investigating potential functional differences in cortical regions of the brains of men and women.

"It is well-known that chronic pain affects 3 times as many women as men, but no one has a clue why this is. We are going to look at resting-state levels initially in healthy females and males and ultimately in individuals with chronic pain to determine whether the default network is different between the sexes," he said.

The study was supported by the National Institutes of Health.

J Neurosci. 2008;28:1398-1403.
Posted on 02/08/08, 06:02 pm