Complex Regional Pain Syndrome

Complex regional pain syndrome (CRPS), formerly Reflex Sympathetic Dystrophy or Causalgia, is a chronic progressive disease characterized by severe pain, swelling, and changes in the skin. It often affects an arm or a leg and may spread to another part of the body and is associated with dysregulation of the autonomic nervous system resulting in multiple functional loss, impairment, and disability. 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. Most information commonly available about CRPS, including this Wikipedia source, relate information more accurately about Type I CRPS. Type II CRPS tends towards the more painful and difficult to control aspects of CRPS, and the three main types of CRPS listed in this article relate mainly to Type I, also. In Type II the "cause" of the syndrome is the known or obvious injury, although the cause of the mechanisms of CRPS Type II are as unknown as the mechanisms of Type I.

The cause of this syndrome is currently unknown. Precipitating factors include injury and surgery, although there are documented cases that have no demonstrable injury to the original site.