Reflex Sympathetic Dystrophy (RSD) is a complex pain syndrome in which the sympathetic nervous system overacts or misfires, causing a person to experience any number of painful symptoms. The condition generally affects the skin, nervous system, blood vessels, and bones. In 1993, the International Association for the Study of Pain (IASP) changed the name of RSD to Complex Regional Pain Syndrome (CRPS). For a while, therefore, RSD and CRPS were synonymous with each other, and the terms were used interchangeably.
In 1994, the IASP reclassified CRPS to include two different variations, labeled as CRPS type I and CRPS type II. This new classification created a technical difference between RSD and CRPS type II. CRPS type I still refers to the condition otherwise known as RSD. On the other hand, CRPS type II is used to refer to a condition formerly known as causalgia, that is, a chronic pain syndrome directly resulting from a specific nerve injury.
RSD and CRPS type I are generally caused by a mild to severe trauma, such as a sprain, broken bone, or contusion. The condition can also be traced to other causes, such as surgery or severe infection. Causalgia, now more commonly referred to as CRPS type II, is different from RSD in that it is typically caused by a nerve injury to a person’s extremities, such as a crush injury or knife wound.
Although RSD and CRPS type II are different as to their causes, they are identical in the variety of symptoms they can cause. RSD and CRPS types I and II are characterized by pain that extends beyond the site of the causative injury. For instance, a person may have suffered an injury to his or her arm but experiences symptoms in his or her neck or legs. The symptoms can range from relatively mild to completely debilitating. They can include a burning pain, swelling, stiffness, and extreme sensitivity to touch. Symptoms of advanced RSD and CRPS types I and II can also include severe muscle atrophy and a decrease in bone density.
The diagnosis techniques used for RSD and CRPS type II also differ. CRPS type II is usually diagnosed by tracing it back to the initial nerve injury. Unlike CRPS type II, the exact cause of RSD or CRPS type I can sometimes be difficult to pinpoint. Various types of studies, such as X-rays, bone scans, and skin tests have been used to diagnose RSD or CRPS type I. Joint fluid analysis and certain thermographic studies have also been used as diagnostic tools for each of these conditions.