Definition and Overview
Complex regional pain syndrome (CRPS) is a chronic pain condition that persists beyond the normally expected healing period following trauma, surgery, or nerve injury. The intensity and duration of pain are unbalanced with the triggering stimulus, and are accompanied by autonomic dysfunction, movement disorders, and nutritional changes.
CRPS Type I occurs without obvious nerve damage and was previously called reflex sympathetic dystrophy (RSD). CRPS Type II occurs after direct damage to peripheral nerves and was previously called causalgia.
The incidence is approximately 5 to 26 per 100,000 population, and is approximately 3 to 4 times more common in women. It occurs slightly more frequently in the upper extremities (after a wrist fracture) than in the lower extremities.
Causes and Mechanisms
neuroinflammation
After trauma, the release of neuropeptides such as Substance P and CGRP continues from peripheral sensory nerves, causing vasodilation, edema, and inflammation. This neurogenic inflammation abnormally persists even after the normal tissue healing response.
central sensitization
Continuous input of peripheral pain signals sensitizes pain processing neurons in the dorsal horn of the spinal cord (central sensitization), causing extreme pain even with mild stimulation. Reorganization of the brain's pain processing circuitry and body schema also contributes to the sensory and motor abnormalities of CRPS.
Sympathetic overactivation
Abnormal sympathetic nerve activity in the affected limb is involved in maintaining pain. There are cases where abnormal sensitivity of peripheral sensory nerves to norepinephrine is formed, resulting in sympathetically maintained pain (SMP), in which pain worsens when sympathetic nerves are activated.
symptoms
Budapest diagnostic criteria
The official diagnostic criteria for CRPS are the Budapest Criteria (2010).
Clinician Criteria: Must have symptoms in at least 3 of the following 4 categories and signs in at least 2 of the following 4 categories:
1. Sensory: Symptoms or signs of allodynia, hyperalgesia 2. Vasomotor: Symptoms or signs of skin temperature asymmetry and skin color changes 3. Sweating/Swelling: Symptoms or signs of abnormal sweating and swelling of extremities. 4. Exercise/Nutrition: Symptoms or signs of decreased range of motion, movement disorders (tremors, dystonia, muscle weakness), nutritional changes (hair, nails, skin)
Additionally, the symptoms must not be better explained by another diagnosis.
Stage
- Acute stage (weeks to months): Pain, swelling, skin warmth and redness
- Dystrophy phase (several months to years): Reduction of edema, skin cooling, skin and hair changes
- Atrophic phase (several years): skin atrophy, joint contractures, osteoporosis
treatment
Physical therapy and occupational therapy
The role of physical therapy in CRPS treatment is key. ‘Desensitization’ training and graded motor imagery (GMI), which gradually activate the affected limb within the pain range, are effective.
Studies have shown that progressive motor imagery therapy significantly improved pain intensity and function in patients with CRPS over the long term.
medication
- Nonsteroidal anti-inflammatory drugs (NSAIDs): Control acute pain and inflammation.
- Pregabalin, Gabapentin: Control of neuropathic pain.
- Antidepressants (amitriptyline, duloxetine): Central sensitization and pain control.
- Bisphosphonates: Reduce bone resorption, some studies report improvement in pain
- Steroids: short-term use in the acute inflammatory phase.
Nerve block treatment
Sympathetic nerve blocks are used to relieve pain and improve the ability to perform physical therapy in CRPS patients with confirmed SMP. For upper extremity CRPS, stellate ganglion block is performed, and for lower extremity CRPS, lumbar sympathetic nerve block is performed.
Spinal Cord Stimulation (SCS)
There is evidence that spinal cord stimulation is effective in controlling long-term pain in chronic CRPS that does not respond to conservative treatment.