P67-T The value of Sympathetic Skin Response in diagnosing Complex Regional Pain Syndrome

Abstract

CPRS is a highly painful disorder affecting a limb, usually following traumatic injury. The syndrome includes continuous pain, inflammation and tissue hypoxia, sympathetic dysregulation, small fibre damage, serum antibodies, central sensitization and cortical reorganization. The diagnosis is clinical and can be supported by complementary bone scintigraphy and thermography. Our purpose is to evaluate the role of Sympathetic Skin Response (SSR) in diagnosing CPRS. A prospective and descriptive study was carried out with 51 patients in initial stages of CPRS. SSR was measured in affected and unaffected hands or feet after 3 stimuli applied to contralateral median or posterior tibial nerves. Values were considered abnormal when peak to peak amplitude response was >50% compared to contralateral extremity. Thermal sensory and pain thresholds were also evaluated. Clinical symptoms and signs were recorded: continuous pain, allodynia, changes in thermoalgesic sensitivity, hyperalgesia, inflammation, swelling and limb dysfunction. We studied the correlation between clinical signs and SSR changes. Mobility impairment was found in 78% of patients, followed by swelling (68%), sweating (37%) and allodynia (24%). SSR was abnormal in 49% of patients, who presented a significant correlation between abnormal SSR response, swelling, thermal sensory thresholds and temperature changes (p < 0.05). SSR can be a useful tool for CPRS diagnosis. It may be used as a means of documenting sympathetic dysfunction and help in treatment decision management as it assists in the clarification of the many controversies regarding the cause of CPRS, which remains unknown.