74 a Human Experimental Immobilization Model and Complex Regional Pain Syndrome

Complex Regional Pain Syndrome (CRPS) type I and II are as the name indicate complex conditions with unclear pathology and unsolved underlying mechanisms. The main clinical characteristics of CRPS are: spontaneous pain, hyperalgesia, movement disorders with bradykinesia, tremor and dystonia, edema, autonomic and trophic changes in skin and adjacent subcutaneous and muscle tissue. Symptoms and objective findings are localized distally in limbs but the distribution of symptoms and signs does not correspond to the innervation territory of any specific nerve. Troels S. Jensen will present the main clinical characteristics of CRPS and link them to findings with pure nerve injury and discuss similarities and differences between CRPS and neuropathic pain. The lack of human models for CRPS may be one of the reasons for our ignorance in understanding the pathohysiology of CRPS. Dr. Astrid Terkelsen will present a human forearm immobilization model mimicking some of the features seen in CRPS. This model induces signs and symptoms of CRPS with movement-induced pain, increased hair growth, cold and mechanical hyperalgesia and reduced capsaicin induced pain and flare. These symptoms are discussed in relation to central symptoms in CRPS. Over the last years interesting findings have emerged showing how tissue or nerve injury may induce spinal plasticity (central sensitization), which alters sensory transmission and sensorimotor processing in the spinal cord and is associated with disinhibition. Anthony Dickenson wil give an overview of the main elements of central sensitization including wind-up and long term potentiation and how these can be targeted pharmacologically. In a final debate the audience is invited to contribute to a pathophysiological discussion of the CRPS syndrome.