Complex regional pain syndrome (CRPS), also known as reflex sympathetic dystrophy (RSD), is a disorder of a portion of the body, usually starting in a limb, which manifests as extreme pain, swelling, limited range of motion, and changes to the skin and bones. One version of the McGill pain index, a scale for rating pain, ranks CRPS highest, above childbirth, amputation and cancer.. It may initially affect one limb and then spread throughout the body; 35% of affected people report symptoms throughout their whole bodies. There are multiple names for this disease, as well as two subtypes. Type I (originally called reflex sympathetic dystrophy (RSD)) occurs after an illness or injury with no direct evidence of nerve damage in the affected limb. This is approximately 90% of CRPS patients. Type II (causalgia) has distinct evidence of a nerve injury. Complex regional pain syndrome is uncommon, and its cause isn't clearly understood. Treatment is most effective when started early. In such cases, improvement and even remission are possible. CRPS typically develops after an injury, surgery, heart attack, or stroke. The pain is out of proportion to the initial even. Treatment involves a multidisciplinary approach involving medications, physical and psychological treatments, combined with sympathetic block and neuromodulation Treatment is most effective when started early in the course of the illness