What Is Complex Regional Pain Syndrome (CRPS)?
Complex regional pain syndrome (CRPS) is a chronic pain condition that is believed to be the result of dysfunction in the central or peripheral nervous systems. Older terms used to describe complex regional pain syndrome are:
- reflex sympathetic dystrophy syndrome (RSDS)
Causalgia was a term first used during the Civil War to describe the intense, hot pain felt by some veterans long after their wounds had healed.
Typical features of complex regional pain syndrome include dramatic changes in the color and temperature of the skin over the affected limb or body part, accompanied by:
- intense burning pain
- skin sensitivity
CRPS I is frequently triggered by tissue injury; the term describes all patients with the above symptoms but with no underlying nerve injury.
Patients with CRPS II experience the same symptoms but their cases are clearly associated with a nerve injury.
Complex regional pain syndrome can strike at any age and affects both men and women, although most experts agree that it is more common in young women.
What Are the Symptoms of Complex Regional Pain Syndrome (CRPS)?
The key symptom of complex regional pain syndrome is continuous, intense pain out of proportion to the severity of the injury (if an injury has occurred), which gets worse rather than better over time. Complex regional pain syndrome most often affects one of the extremities such as:
Complex regional pain syndrome is also often accompanied by:
- "burning" pain
- increased skin sensitivity
- changes in skin temperature: warmer or cooler compared to the opposite extremity
- changes in skin color: often blotchy, purple, pale, or red
- changes in skin texture: shiny and thin, and sometimes excessively sweaty
- changes in nail and hair growth patterns
- swelling and stiffness in affected joints
- motor disability, with decreased ability to move the affected body part
Often the pain spreads to include the entire arm or leg, even though the initiating injury might have been only to a finger or toe. Pain can sometimes even travel to the opposite extremity. It may be heightened by emotional stress.
The symptoms of complex regional pain syndrome vary in severity and length. Some experts believe there are three stages associated with complex regional pain syndrome, marked by progressive changes in the skin, muscles, joints, ligaments, and bones of the affected area, although this progression has not yet been validated by clinical research studies.
- Stage one is thought to last from 1 to 3 months and is characterized by severe, burning pain, along with muscle spasm, joint stiffness, rapid hair growth, and alterations in the blood vessels that cause the skin to change color and temperature.
- Stage two lasts from 3 to 6 months and is characterized by intensifying pain, swelling, decreased hair growth, cracked, brittle, grooved, or spotty nails, softened bones, stiff joints, and weak muscle tone.
- In stage three the syndrome progresses to the point where changes in the skin and bone are no longer reversible. Pain becomes unyielding and may involve the entire limb or affected area. There may be marked muscle loss (atrophy), severely limited mobility, and involuntary contractions of the muscles and tendons that flex the joints. Limbs may become contorted.
What Causes Complex Regional Pain Syndrome (CRPS)?
Doctors aren’t sure what causes complex regional pain syndrome. In some cases the sympathetic nervous system plays an important role in sustaining the pain. The most recent theories suggest that pain receptors in the affected part of the body become responsive to a family of nervous system messengers known as catecholamines.
Animal studies indicate that norepinephrine, a catecholamine released from sympathetic nerves, acquires the capacity to activate pain pathways after tissue or nerve injury. The incidence of sympathetically maintained pain in complex regional pain syndrome is not known. Some experts believe that the importance of the sympathetic nervous system depends on the stage of the disease.
Another theory is that post-injury complex regional pain syndrome (CRPS II) is caused by a triggering of the immune response, which leads to the characteristic inflammatory symptoms of redness, warmth, and swelling in the affected area. Complex regional pain syndrome may therefore represent a disruption of the healing process. In all likelihood, complex regional pain syndrome does not have a single cause, but is rather the result of multiple causes that produce similar symptoms.