Complex Regional Pain Syndrome (CRPS) is a chronic progressive disease characterized by severe pain, swelling, and changes in the skin. Though treatment is often unsatisfactory, early multimodal therapy can cause dramatic improvement or remission of the syndrome in some patients. The International Association for the Study of Pain has proposed dividing CRPS into two types based on the presence of nerve lesion following the injury. Type I, formerly known as reflex sympathetic dystrophy (RSD), Sudeck's atrophy, reflex neurovascular dystrophy (RND), or algoneurodystrophy, does not have demonstrable nerve lesions. Type II, formerly known as causalgia, has evidence of obvious nerve damage. The cause of this syndrome is currently unknown. Precipitating factors include injury and surgery, although documented cases have shown no demonstrable injury to the original site.