Joint Pain Forum – News you can use!
Role of
emotions in how patients feel arthritis pain
Medical Research News
Published: Friday, 30-Mar-2007 How does the brain process the experience of
pain? Thanks to advances in neuroimaging, we now know the answer lies
in a network of brain structures called the pain matrix. This matrix
contains two parallel systems. The medial pain system processes the
emotional aspects of pain, including fear and stress, while the lateral
system processes the physical sensations - pain's intensity, location,
and duration.
Marked by morning stiffness, joint aches,
and flare-ups, the pain of arthritis tends to be acute and recurrent,
in contrast to many chronic pain conditions. Arthritis pain therefore
makes an ideal model for comparing common clinical pain with
experimental pain. Inspired by this observation, researchers at
University of Manchester Rheumatic Diseases Centre in the United
Kingdom conducted the first study to compare directly the brain areas
involved in processing arthritis pain and experimental pain in a group
of patients with osteoarthritis (OA). Their results, published in the
April 2007 issue of Arthritis & Rheumatism
(http://www.interscience.wiley.com/journal/arthritis),
shed light on the role of emotions in how patients feel arthritis pain.
The study focused on 12 patients with knee
OA - 6 women and 6 men, with a mean age of 52 years. All subjects
underwent positron emission tomography (PET), to measure and map
18F-fluorodeoxyglucose (FDG) uptake in the brain as an indicator of
brain activity. PET scans were performed during three different pain
conditions: arthritic knee pain; experimental pain, achieved by heat
application; and pain-free. The brain responses to each pain state were
then rigorously examined and statistically evaluated and compared for
significant differences.
In
all OA subjects, both pain conditions activated the entire pain matrix.
However, during arthritic pain, activity was increased within the
medial pain system of the brain, including most of the cingulate
cortex, the thalamus, and the amygdala. This suggests that, for these
patients, arthritis pain has more emotional impact - and perhaps
stronger associations with fear and distress - than experimental pain.
Arthritis pain also prompted heightened activation of the prefrontal
cortex and the inferior posterior parietal cortex, areas of the brain
instrumental in the supervision of attention. Their activation while
suffering arthritis pain may reflect the patients' concentration on
coping strategies.
"The present study demonstrates the
importance of the medial pain system during the experience of arthritic
pain and suggests that it is a likely target for both pharmacologic and
nonpharmacologic interventions," notes its leading author, Prof. A.K.P.
Jones. "Considering the recent concerns about the long-term safety of
cyclo-oxygenase inhibitors, we hope that our current findings will
stimulate partnerships between academia and the pharmacological
industry to develop a new class of analgesics for arthritic pain that
specifically target the medial pain system."
As Prof. Jones acknowledges, the study's
main limitation is its small number of subjects. Larger studies of the
relationship between arthritis pain and the medial pain system are
critical, particularly for exploring the effect of variables from
depression and anxiety to guided imagery, meditation, and other
mind-based pain management techniques. "Researchers should be moving
toward more naturalistic studies in patients," Prof. Jones suggests,
"in order to fully understand the perception of different types of
clinical pain."
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