CRPS is more prevalent in women, but can occur in men. It can occur at any age, but peaks at age 40. It is rarely seen in the elderly and children.
 

Most cases of CRPS is caused by trauma or injury. However, there may be rare cases of CRPS without trauma or cases of severe trauma without CRPS. The most common injuries are fractures, sprains, burns, bruises, cuts, limb immobilization (limb cast or splint), surgery or needles sticks. CRPS is an abnormally painful response to an injury.

In healthy individuals, myelin surrounds the peripheral sensory nerve fibers, called axons, that deliver the sensation of pain and sends messages to the blood vessels. In affected individuals the axon or nerves are unmyelinated or thinly myelinated and potentiates the feeling of pain. In CRPS, the symptoms are triggered by damage to nerve fibers in close proximity with blood vessels, producing inflammation and pain. The blood vessels can over constrict and cause white/blue skin or dilate and cause red/swollen skin. Damage to these nerves can trigger further damage in the spinal cord and/or brain.

There is limited data on CRPS being cause by genetics.

The primary symptom is constant severe pain. The pain is often described as a burning, squeezing, or “pins and needles” sensation. The pain typically radiates throughout the limb even if the initial injury was only on a toe or finger. The pain can also travel to the opposite limb in rare cases. Increased sensitivity to pain is common in the affected area called allodynia.

Other symptoms of CRPS include the following:

• Inflammation or swelling
• Changes in the skin texture – thin or shiny
• Abnormal sweating patterns
• Changes in nail and hair growth
• Stiff joints in affected limb
• Decreased muscle coordination and movement in affected limb
• Abnormal movements in affected limb – fixed abnormal posture (dystonia), tremors, jerking, or twitching
• Excess bone resorptions – cell breaks down the bone and release calcium into the blood

Diagnosis is based a clinical evaluation of the patient’s symptoms and medical history. Detailed examination by a doctor or specialist is important to rule out other conditions with similar symptoms. Most affected individuals can have symptom improvement over time. Diagnosis can be difficult in the latter end of the condition.
 

There is no specific test to confirm or diagnose CRPS. Magnetic resonance imaging (MRI) or triple phase bone scans can help confirm a diagnosis.
 

Rehabilitation or physical therapy is the primary treatment. Exercise can help keep the affected limb mobile, improved flexibility and strength, increase blood flow, and decrease symptoms. Rehabilitation helps improve motion and slow-down secondary brain changes due to the chronic pain. Occupational therapy can help individuals learn new ways to do daily tasks.

There is currently no FDA-approved (U.S. Food and Drug Administration) medication indicated specifically for CRPS. There are drugs that can help manage or improve CPRS symptoms, such as:

• Bisphosphonates for bone health
• Non-steroidal anti-inflammatory drugs (NSAIDS) for pain and swelling
• Steroids for swelling and inflammation
• Drugs to treat neuropathic pain, such as gabapentin, pregabalin, amitriptyline, nortriptyline, an duloxetine
• Botulinum toxin injections for pain and stiffness
• Topical creams and patches for pain
• Many of the above listed drugs have several side effects. It is best to review side effects and report issues to the doctor.

There are other treatments that have been tried, but not proven effective, such as: sympathetic nerve block, surgical sympathectomy, spinal cord stimulation, and neural stimulation.

Other treatments in the trial phase are intravenous immunoglobulin (IVIG) and graded motor imagery. Graded motor imagery is the process of doing mental exercises in front of the mirror and visualize moving the painful body parts without moving them.

Alternative therapies are acupuncture, behavior modification, chiropractic treatment, and relaxation techniques.

The outcome of CRPS is variable. Affected individuals with mild to moderate symptom and pain can recover. Affected individuals with severe and debilitating symptom and pain may not recover and may have long-term disability. Younger individuals typically have better outcomes than older individuals.

https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Complex-Regional-Pain-Syndrome-Fact-Sheet%20

https://orthoinfo.aaos.org/en/diseases--conditions/complex-regional-pain-syndrome-reflex-sympathetic-dystrophy/