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
Their findings are published in the issue of the journal Arthritis
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.
"That capability seems to be dampened, if not
eliminated for people with fibromyalgia, " Webster said.
"They may not be able to respond the same
way to medications or our intrinsic [natural] mechanisms for dealing with
No one knows what causes
fibromyalgia, which involves widespread joint and muscle pain.
The disorder affects
3.4% of women and 0.5% of men in the United States, according to the study.
Older women are most likely to suffer from fibromyalgia, which affects more
than 7% of women aged 60 to 79.
A total of 31 patients with fibromyalgia and 14 healthy people were involved in the study.
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.
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 100.
"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 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 centre 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
"We didn't see this in people with fibromyalgia. The activation is
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 centre of the brain that plays a role in pain transition.
Loggia said: "In
animals, it has been shown that if you electrically stimulate this area, pain
responses go down."
The PAG activates in
healthy people who have received a cue that pain is imminent, as they prepare
themselves for the pain to come.
The region, however, doesn't 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 Centre.
However, there are some
drawbacks to the study and its conclusions.
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.
volunteers go from a state of no pain to a state of pain, 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," said Loggia.
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 US
National Library of Medicine.