TUESDAY, Nov. 5 (HealthDay News) -- Brain scans reveal that
people with fibromyalgia are not as able to prepare for pain as
healthy people, and they are less likely to respond to the promise
of pain relief.
This altered brain processing could explain why people with the
mysterious chronic ailment feel pain more intensely and don't
respond as well to narcotic painkillers, the researchers said.
Their findings are published in the Nov. 5 issue of the journal
Arthritis & Rheumatism.
People without fibromyalgia can mentally alleviate some types of
pain that people experience, explained Dr. Lynn Webster, president
of the American Academy of Pain Medicine. "For people with
fibromyalgia, that capability seems to be dampened if not
eliminated," Webster said. "They may not be able to respond the
same way to medications or our intrinsic [natural] mechanisms for
dealing with pain."
No one knows what causes fibromyalgia, which involves widespread
joint and muscle pain. The disorder affects 3.4 percent of women
and 0.5 percent of men in the United States, according to the
study. Older women are most likely to suffer from fibromyalgia,
which affects more than 7 percent of women aged 60 to 79.
Researchers conducted this study using 31 patients with
fibromyalgia and 14 healthy people.
The study authors used an MRI to scan each participant's brain
as a blood pressure cuff painfully squeezed the patient's calf,
said study author Dr. Marco Loggia, from Massachusetts General
Hospital and Harvard Medical School in Boston. Doctors tailored the
pressure provided by the cuff so that everyone with or without
fibromyalgia would rate their pain between 40 to 50 on a scale of
"It gives a very deep, muscular type of pain," Loggia said. "It's closer to the clinical pain that a patient with fibromyalgia experiences."
Patients also received a visual cue that told them when the cuff
would begin squeezing their calf and when the cuff would release
its grip, allowing researchers to see how the brain would respond
to anticipation of both pain and relief.
As expected, the people with fibromyalgia needed much less
pressure to reach the same pain rating as a healthy person, Loggia
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,
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
However, there are some drawbacks to the study and its
Loggia noted that the altered brain activity could be explained
away by the fact that fibromyalgia patients endure constant pain
and the disorder has altered the brain response, instead of the
other way around.
"The healthy volunteers go from a state of no pain to a state of pain," he said. "But fibromyalgia patients go from a lower level of pain to a higher level of pain, which could affect the way they process the pain and relief cues."
In addition, the researchers failed to compare the response of
fibromyalgia patients to that of people with other chronic pain
conditions, Kassel said.
"This may not be something caused by fibromyalgia," he said. "It could be something that just happens in most chronic pain patients."
For more information on fibromyalgia, visit the
U.S. National Library of Medicine.
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