"While the debate has raged, neuroscientists have begun to use brain scan technology to identify the areas of the normal human brain that become most active during pain. A few studies have even assessed the blood flow in those areas in fibromyalgia patients during baseline brain scans. The new study is the first to use both high-speed scanning and a painful stimulus.
In the study, fibromyalgia patients and healthy control subjects had their brains scanned for more than 10 minutes while a small, piston-controlled device applied precisely calibrated, rapidly pulsing pressure to the base of their left thumbnail. The pressures were varied over time, using painful and non-painful levels that had been set for each patient prior to the scan.
The study's design gave two opportunities to compare patients and controls: the pressure levels at which the pain rating given by patients and control subjects was the same, and the rating that the two different types of participants gave when the same level of pressure was applied.
The researchers found that it only took a mild pressure to produce self-reported feelings of pain in the fibromyalgia patients, while the control subjects tolerated the same pressure with little pain.
"In the patients, that same mild pressure also produced measurable brain responses in areas that process the sensation of pain," says Clauw. "But the same kind of brain responses weren't seen in control subjects until the pressure on their thumb was more than doubled."
Though brain activity increased in many of the same areas in both patients and control subjects, there were striking differences too. Patients feeling pain from mild pressure had increased activity in 12 areas of their brains, while the control subjects feeling the same pressure had activation in only two areas. When the pressure on the control subjects' thumbs was increased, so did their pain rating and the number of brain areas activated. But only eight of the areas were the same as those in patients' brains.
In all, the fibromyalgia patients' brains had both some areas that were activated in them but not in controls, and some areas that stayed "quiet" in them but became active in the brains of controls feeling the same level of pain. This response suggests that patients have enhanced response to pain in some brain regions, and a diminished response in others, Clauw says.
The study was supported in part by the National Fibromyalgia Research Association, the U.S. Army and the NIH. In addition to Clauw and Gracely, the research team included Frank Petzke, M.D.; and Julie M. Wolf, BA"
Summary of original article
Arthritis & Rheumatism
Volume 46, Issue 5, pages 1333–1343, May 2002
Functional magnetic resonance imaging evidence of augmented pain processing in fibromyalgia
Article first published online: 8 MAY 2002