Arthritis pain processed in the brain's 'fear zone'
April 2007Researchers in the School of Medicine’s Division of Medicine and Neurosciences have discovered that arthritis pain is processed in the parts of the brain concerned with emotions and fear.
A team led by Dr Bhavna Kulkarni of the Human Pain Research Group has captured the first images of how the brain processes arthritis pain, using positron emission tomography (PET) scanning.
In a study published in 'Arthritis and Rheumatism', they compare the brain areas involved in processing arthritic and experimental pain in patients with osteoarthritis of the knee. 12 patients underwent PET brain-scanning during three different pain states: arthritic knee pain, experimental knee pain and a pain-free state.
Bhavna said: “We knew that experimentally-induced pain is processed in at least two brain networks; the ‘medial pain system’ processing the emotional aspects such as unpleasantness while the ‘lateral pain system’ processes intensity, location and duration. We wanted to see whether the same applied to the clinical pain suffered by people with conditions like arthritis.
“Although arthritic and experimental pain each activated both the medial and lateral pain systems, arthritic pain prompted increased activity in the parts of the medial system concerned with processing fear, emotions and aversive conditioning.
“This suggests that arthritic pain has more emotional salience than experimental pain for these patients. The increased activity in the areas associated with aversive conditioning, reward and fear, which are less commonly activated during experimental pain, suggests they might be processing fear of further injury and disability associated with the arthritic pain.”
Supervisor Professor Anthony Jones said: “It seems that studying experimental pain alone doesn’t provide a complete picture, and that PET scanning patients experiencing different types of clinical pain can reveal subtle changes in brain activity.
“Importantly, this study has also demonstrated the importance of the medial pain system during arthritic pain, suggesting it would be a good target for both new analgesics and non-pharmacological interventions. The body’s own pain-killing chemicals could even be modulated, to target pain in the areas we have identified.”
