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Complex Regional Pain Syndrome (CRPS) is a chronic pain condition affecting a limb, usually after injury or surgery, characterized by prolonged or excessive pain, changes in skin color/temperature, swelling, and motor/sensory disturbances that are disproportionate to the inciting event.

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https://www.youtube.com/watch?v=l_yWmYcNFas

https://www.youtube.com/watch?v=bCXO3g7rdLA

Classification

Budapest criteria classification:

Type	Description
CRPS Type I	No confirmed nerve injury (formerly reflex sympathetic dystrophy)
CRPS Type II	Confirmed nerve injury (formerly causalgia)

Diagnostic criteria

Budapest diagnostic criteria for CRPS: https://doi.org/10.1016/j.pain.2010.04.030

Must have continuing pain disproportionate to any inciting event and:

≥1 symptom in 3 of 4 categories:
- Sensory: Hyperesthesia, allodynia
- Vasomotor: Temperature or color asymmetry
- Sudomotor/edema: Edema, sweating changes or asymmetry
- Motor/trophic: Decreased ROM, weakness, tremor, trophic changes (nails, hair, skin)
≥1 sign in ≥2 of 4 categories at evaluation
No other diagnosis better explains the signs/symptoms

Pathophysiology

Multifactorial and not fully understood; involves:

Peripheral nerve sensitization
Central sensitization
Dysregulation of the autonomic nervous system