Complex Regional Pain Syndrome (CRPS) is a painful condition associated with autonomic, motor and trophic changes. It most often affects one limb (arm, leg, hand, or foot), typically after an injury, which causes damage to the peripheral and central nervous systems. CRPS is rare in extremes of ages but can occur at any age, It is more common in women.
There are two types of CRPS: Type 1 is CRPS without a definable nerve lesion (previously known as reflex sympathetic dystrophy), and type 2 (previously known as causalgia) with a definable nerve lesion. However, this classification may be arbitrary as the treatment is similar. The symptoms of CRPS vary in severity ranging from being self-limiting to quite debilitating.
CRPS is characterized by prolonged or excessive pain and changes in skin color, temperature, and/or swelling in the affected area. The pain has been described as “burning,” along with the “pins and needles” sensation, which may spread to the entire arm or leg. In rare cases, pain can sometimes even travel to the opposite extremity. There is often increased sensitivity in the affected area (allodynia). People also complain of changes in the skin temperature, skin color, or swelling of the affected limb, which occur due to abnormal microcirculation secondary to nerve damage. Other common symptoms include changes in nail and hair growth patterns, joint stiffness, poor muscle coordination, etc.
The most common triggers for CRPS include fractures, sprains/strains, soft tissue injury, limb immobilization, surgery, etc. It occurs due to an abnormal response to such an injury. This exaggerated response may be due to abnormal demyelination of the peripheral nerves carry the pain signals from the extremities. Some of these nerves communicate with blood vessels, resulting in the vascular symptoms seen in CRPS.
CRPS is a clinical diagnosis. There is no specific test that can confirm the diagnosis, based on a careful history and physical examination. The diagnosis of CRPS may be confused with that of arthritis, Lyme disease, generalized muscle diseases, a clotted vein, or small fiber polyneuropathies. Magnetic resonance imaging or triple-phase bone scans may be performed to help with the diagnosis.
The outcome of CRPS is quite variable – younger patients are found to have better outcomes, while some older patients experience severe symptoms refractory to all treatment. Early treatment, particularly rehabilitation may help in some cases. Treatment includes rehabilitation and physical therapy. Psychotherapy can help prevent or limit profound psychological symptoms associated with chronic CPRS, which include depression, anxiety, or post-traumatic stress disorder.
No single drug or combination of drugs is found to be curative for CRPS. Drugs that have been used to for symptomatic relief include bisphosphonates, non-steroidal anti-inflammatory drugs, corticosteroids, gabapentin, pregabalin, amitriptyline, nortriptyline, and duloxetine, botulinum toxin injections, and even opioids such as oxycodone, morphine, hydrocodone, and N-methyl-D-aspartate (NMDA) receptor antagonists such as dextromethorphan and ketamine. These drugs can have serious side effects such as drowsiness, dizziness, increased heartbeat, and impaired memory, and should be used/prescribed with caution. In some cases, sympathetic nerve blocks are performed.
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