Wiley Inner Science
19 December 2006
http://tinyurl.com/2fn93o

Research Article
Arthritic pain is processed in brain areas concerned with emotions and fear
B. Kulkarni 1 *, D. E. Bentley 1, R. Elliott 2, P. J. Julyan 3, E. Boger 1, A. Watson 1, Y. Boyle 1, W. El-Deredy 1, A. K. P. Jones 1
1University of Manchester Rheumatic Diseases Centre, Hope Hospital, Salford, UK
2University of Manchester, Manchester, UK
3Christie Hospital National Health Service Trust, Withington, Manchester, UK
 
email: B. Kulkarni ( This e-mail address is being protected from spam bots, you need JavaScript enabled to view it )

*Correspondence to B. Kulkarni, Human Pain Research Group, University of Manchester Rheumatic Diseases Centre, Hope Hospital, Eccles Old Road, Salford M6 8HD, UK

Funded by:
 Arthritis Research Campaign, UK

Abstract

Objective
Functional neuroimaging studies have shown that experimentally induced acute pain is processed within at least 2 parallel networks of brain structures collectively known as the pain matrix. The relevance of this finding to clinical pain is not known, because no direct comparisons of experimental and clinical pain have been performed in the same group of patients. The aim of this study was to compare directly the brain areas involved in processing arthritic pain and experimental pain in a group of patients with osteoarthritis (OA).

Methods
Twelve patients with knee OA underwent positron emission tomography of the brain, using 18F-fluorodeoxyglucose (FDG). Scanning was performed during 3 different pain states: arthritic knee pain, experimental knee pain, and pain-free. Significant differences in the neuronal uptake of FDG between different pain states were investigated using statistical parametric mapping software.

Results
Both pain conditions activated the pain matrix, but arthritic pain was associated with increased activity in the cingulate cortex, the thalamus, and the amygdala; these areas are involved in the processing of fear, emotions, and in aversive conditioning.

Conclusion
Our results suggest that studies of experimental pain provide a relevant but quantitatively incomplete picture of brain activity during arthritic pain. The search for new analgesics for arthritis that act on the brain should focus on drugs that modify this circuitry.