In a new study, investigators at Northwestern University's Feinberg
School of Medicine have identified a clue that may explain how
suffering long-term pain could trigger these other pain-related
symptoms.

Researchers found that in a healthy brain all the regions exist in a
state of equilibrium. When one region is active, the others quiet
down. But in people with chronic pain, a front region of the cortex
mostly associated with emotion "never shuts up," said Dante Chialvo,
lead author and associate research professor of physiology at the
Feinberg School. "The areas that are affected fail to deactivate when
they should."

They are stuck on full throttle, wearing out neurons and altering
their connections to each other.

This is the first demonstration of brain disturbances in chronic pain
patients not directly related to the sensation of pain.

Chialvo and colleagues used functional magnetic resonance imaging
(fMRI) to scan the brains of people with chronic low back pain and a
group of pain-free volunteers while both groups were tracking a moving
bar on a computer screen. The study showed the pain sufferers
performed the task well but "at the expense of using their brain
differently than the pain-free group," Chialvo said.

When certain parts of the cortex were activated in the pain-free
group, some others were deactivated, maintaining a cooperative
equilibrium between the regions. This equilibrium also is known as the
resting state network of the brain. In the chronic pain group,
however, one of the nodes of this network did not quiet down as it did
in the pain-free subjects.

This constant firing of neurons in these regions of the brain could
cause permanent damage, Chialvo said. "We know when neurons fire too
much they may change their connections with other neurons and or even
die because they can't sustain high activity for so long," he
explained.

'If you are a chronic pain patient, you have pain 24 hours a day,
seven days a week, every minute of your life," Chialvo said. "That
permanent perception of pain in your brain makes these areas in your
brain continuously active. This continuous dysfunction in the
equilibrium of the brain can change the wiring forever and could hurt
the brain."

Chialvo hypothesized the subsequent changes in wiring "may make it
harder for you to make a decision or be in a good mood to get up in
the morning. It could be that pain produces depression and the other
reported abnormalities because it disturbs the balance of the brain as
a whole."

He said his findings show it is essential to study new approaches to
treat patients not just to control their pain but also to evaluate and
prevent the dysfunction that may be generated in the brain by the
chronic pain.

The study will be published Feb. 6 in The Journal of Neuroscience.
Chialvo's collaborators in this project are Marwan Baliki, a graduate
student; Paul Geha, a post-doctoral fellow, and Vania Apkarian,
professor of physiology and of anesthesiology, all at the Feinberg
School.

Adapted from materials provided by Northwestern University.