Fibromyalgia Patients May Process Pain Differently
Activity in certain regions suggests why they're less able to prepare for pain or respond to pain relief
As expected, the people with fibromyalgia needed much less pressure to reach the same pain rating as a healthy person, Loggia said.
But the doctors also noticed key differences in the way certain parts of their brain dealt with pain before, during and after.
One brain region that showed an altered response was the ventral tegmental area (VTA), a group of neurons in the center of the brain that responds to reward or punishment. The VTA helps regulate the release of dopamine, a pain-relieving brain chemical. It plays a crucial role in a person's response to pain medications and has been linked to drug addiction.
"The VTA in healthy volunteers activated before pain and during pain, and the region deactivated when they received the relief signal. People were more worried about the pain to come and more rewarded by the cue that the pain would soon end," Loggia said. "In people with fibromyalgia, we don't see this. The activation is completely blunted."
The altered response of the VTA also could explain why fibromyalgia patients often do not respond to narcotic painkillers, he added.
The investigators also noted a different response in the periaqueductal gray (PAG), a small structure in the center of the brain that plays a role in pain transition. "In animals, it has been shown that if you electrically stimulate this area, pain responses go down," Loggia said.
The PAG activates in healthy people who have received a cue that pain is imminent, as they prepare themselves for the pain to come. But the region does not activate when people with fibromyalgia are warned of oncoming pain, suggesting that they are less capable of guarding against pain signals, Loggia said.
The study provides "another piece of evidence that in fibromyalgia something is fundamentally amiss, and this idea that it is a peripheral disorder is mistaken," said Dr. John Kassel, a professor of neurology and director of the division of neuromuscular medicine at Ohio State University's Werner Medical Center.
However, there are some drawbacks to the study and its conclusions.