How Complex Regional Pain Syndrome Affects the Body
CRPS causes severe, disproportionate pain in a limb following trauma, accompanied by sensory, autonomic, motor, and trophic dysfunction that progressively worsens without treatment. 1
Pain Characteristics
The hallmark feature is excruciating, burning pain that is disproportionate to the initial injury and worsens with touch or stimulation. 1 This pain gradually increases in intensity and spreads within the affected limb, sometimes extending to the contralateral limb. 2 The pain typically develops 4-6 weeks after direct trauma such as injury or surgery. 3
Sensory Abnormalities
- Allodynia (pain from normally non-painful stimuli) and hyperalgesia (exaggerated pain response) are defining sensory features. 1
- These sensory disturbances result from peripheral and central sensitization mechanisms that amplify pain signals. 4
- CRPS demonstrates minimal placebo response except at very early time points (15-30 minutes), distinguishing it from other pain syndromes. 1
Autonomic Dysfunction
Temperature dysregulation, skin color changes, and abnormal sweating patterns are common autonomic manifestations. 1
- The affected limb may alternate between feeling hot or cold compared to the unaffected side. 1
- Skin color changes include redness, pallor, or cyanosis due to vasomotor instability. 3
- Sudomotor dysfunction causes either excessive sweating or complete absence of sweating in the affected region. 3
- Power Doppler ultrasound demonstrates increased blood flow in the lower extremity with 73% sensitivity and 92% specificity for detecting these vascular changes. 5
Motor Impairment
Functional limb weakness and decreased active range of motion are characteristic motor effects. 1
- Patients develop progressive loss of motor function that extends beyond what would be expected from disuse alone. 4
- Musculoskeletal dystrophy occurs in chronic cases, with muscle atrophy and contractures developing over time. 6
- Motor dysfunction involves both voluntary movement limitations and involuntary tremors or dystonic postures. 7
Trophic Changes
Hair loss, tissue changes, and skin discoloration occur at the pain site, particularly in chronic CRPS. 1, 2
- Skin texture alterations include thinning or thickening of the dermis. 3
- Nail growth abnormalities manifest as brittle, ridged, or excessively curved nails. 4
- Regional bone demineralization develops, visible on imaging as patchy osteoporosis. 6
- Tissue atrophy progresses over months to years if left untreated. 4
Neuroinflammatory Effects
Neurogenic inflammation drives many of the visible changes in CRPS through abnormal nervous system activity. 4
- Inflammatory mediators released by sensitized nerve fibers cause localized swelling and edema. 8
- This inflammation contributes to the heightened pain sensitivity and tissue changes observed clinically. 4
- Maladaptive brain plasticity occurs, with reorganization of cortical representation of the affected limb. 4
Systemic Considerations
CRPS symptoms must be present for at least 12 months to be considered chronic, with distinct pathological characteristics emerging beyond this timepoint. 1, 6
- The condition can develop in spinal cord injury patients, manifesting with the same clinical features. 9
- Potential autoimmune mechanisms may contribute to disease progression in some patients. 4
- Psychological factors including anxiety and avoidance behavior can perpetuate disability. 1
Clinical Pitfall to Avoid
Delaying physical therapy while waiting for pain to resolve worsens outcomes through disuse and pain upregulation. 1 The progressive nature of untreated CRPS leads to irreversible trophic changes, contractures, and permanent functional impairment. 8 Early recognition and immediate initiation of rehabilitation are critical to prevent these complications. 7