Complex regional pain syndrome (CRPS) is a form of chronic pain that usually affects an arm or a leg. It is a neurological condition that causes pain and other symptoms in your extremities, most commonly your hand. CRPS typically develops after an injury, surgery, or other medical condition, but the exact cause is not completely understood. It is thought to be caused by an injury to or difference in the peripheral and central nervous systems. CRPS occurs in two types, with similar signs and symptoms, but different causes:

• Type 1: Also known as reflex sympathetic dystrophy (RSD), this type occurs after an illness or injury that didnt directly damage the nerves in the affected limb. About 90% of people with CRPS have type 1.
• Type 2: Also known as causalgia, this type occurs after a specific nerve injury.

Symptoms of CRPS may change over time and vary from person to person. Pain, swelling, redness, noticeable changes in temperature, and hypersensitivity (particularly to cold and touch) usually occur first. Over time, the affected limb can become cold and pale. It may undergo skin and nail changes as well as muscle spasms and tightening. Once these changes occur, the condition is often irreversible. CRPS occasionally may spread from its source to elsewhere in the body, such as the opposite limb. There is no specific diagnostic test for CRPS, but some testing can rule out other conditions. Triple-phase bone scans can be used to identify changes in the bone and in blood circulation. Some health care providers may apply a stimulus (for example, heat, touch, cold) to determine whether there is pain in a specific area. Treatment for CRPS is most effective when started early and focuses on relieving painful symptoms...