'No-Cause' Back Pain Really Hurts

Patients Have Increased Pain Sensitivity

From the WebMD Archives

Oct. 28, 2002 -- People with long-lasting lower back pain often don't know why they hurt. Now it seems they suffer from a nerve problem that turns up the volume on their pain.

The problem is similar to fibromyalgia. Like fibromyalgia patients, back pain sufferers have no apparent physical reason to hurt. But they do. A brain scan earlier this year proved that fibromyalgia patients are much more sensitive to pain than other people. Now the test shows this is true for people with chronic lower back pain, too.

The report, by researchers led by Richard H. Gracely, PhD, and Daniel J. Clauw, MD, of the University of Michigan, comes at this week's meeting of the American College of Rheumatology.

"These people really don't know what they have and what the future will bring," Gracely told WebMD earlier this year. "It is just a terrible situation to be in. The general lay public doesn't really realize that pain can be very severe and untreatable. People think you can just go get it fixed."

The researchers used a test that applied increasing pressure to the thumbnail bed, eventually causing "slightly intense pain." At the same time, a sophisticated new brain scan called functional magnetic resonance imaging (fMRI) let the researchers see how and where the pain affected brain activity.

When normal people felt the thumbnail pain, the pain centers in their brains lit up. This also happened to back-pain patients -- but at thumbnail pressures that had no effect on normal people.

"Some pathologic process is making these patients more sensitive," Clauw says in a news release. "For some reason -- still unknown -- there's a neurobiological amplification of their pain signals."

Interestingly, back-pain patients had different fMRI patterns than normal people and fibromyalgia patients. Clauw thinks this means that back-pain patients are more sensitive to pain sensations arriving in some areas of the brain, and less sensitive to pain sensations arriving in some other areas.