What are the typical findings that indicate Complex Regional Pain Syndrome (CRPS) in adults with a history of trauma or surgery?

Clinical Findings Indicating Complex Regional Pain Syndrome (CRPS)

CRPS diagnosis is primarily clinical, requiring excruciating pain disproportionate to the initial injury that persists for at least 12 months to be considered chronic, accompanied by sensory, autonomic, motor, and trophic changes based on the Budapest Criteria. 1

Essential Diagnostic Features

Pain Characteristics

• Excruciating, burning pain that is disproportionate to the incinciting trauma or surgery is the hallmark feature 1
• Pain gradually increases in intensity and spreads within the affected limb, sometimes extending to the contralateral limb 1
• Pain worsens with touch or stimulation, distinguishing it from other pain syndromes 1
• The disproportionate nature of pain relative to injury severity is critical for diagnosis 2

Sensory Abnormalities

• Allodynia (pain from normally non-painful stimuli) and hyperalgesia (exaggerated pain response) are hallmark sensory features 1
• These sensory disturbances must be present and documented on physical examination 1

Autonomic Dysfunction

• Temperature dysregulation with asymmetric skin temperature changes between affected and unaffected limbs 1
• Skin color changes (mottling, cyanosis, or erythema) indicating microvascular dysregulation 1, 3
• Abnormal sweating patterns (hyperhidrosis or hypohidrosis) in the affected limb 1
• Edema is a common autonomic feature 3

Motor Impairment

• Functional limb weakness with decreased active range of motion 1
• Motor dysfunction is a characteristic finding that distinguishes CRPS from purely sensory neuropathies 1

Trophic Changes (Chronic Cases)

• Hair loss in the affected region 1
• Skin discoloration and tissue changes 1
• These changes are more prominent in chronic CRPS cases 1

Diagnostic Criteria Application

Budapest Criteria Requirements

• Symptoms must be present for at least 12 months to be considered chronic CRPS 1
• CRPS remains a diagnosis of exclusion—other conditions must be ruled out 1, 4
• The diagnosis requires clinical findings across multiple categories (sensory, autonomic, motor, trophic) 1

Chronic CRPS-Specific Features (≥12 months)

• Musculoskeletal dystrophy becomes more prominent 4
• Neurogenic inflammation persists 4
• Sympathetic dysfunction may evolve 4

Classification: Type I vs Type II

• Type I (formerly reflex sympathetic dystrophy): occurs without identifiable nerve injury 1, 3
• Type II (formerly causalgia): occurs after confirmed nerve injury documented through clinical examination or diagnostic testing 1, 3
• The critical distinction is documentation of nerve injury—its presence defines Type II, while its absence defines Type I 1

Diagnostic Imaging Support

Three-Phase Bone Scintigraphy

• Most useful imaging modality with pooled sensitivity of 78% and specificity of 88% 1
• Cannot distinguish between Type I and Type II 1
• Recommended by the American College of Radiology as first-line imaging 1

MRI Findings

• Higher specificity (91%) but lower sensitivity (35%) for CRPS-I, making it unsuitable as a screening test 1
• More useful in Type II cases for directly visualizing nerve lesions and detecting denervation changes 1
• Can show regional bone demineralization in chronic cases 4

High-Resolution Ultrasound

• May be useful in Type II cases for visualizing nerve pathology and signs of muscle denervation 1

Critical Diagnostic Pitfalls to Avoid

• Do not wait for all signs to be present simultaneously—the Budapest Criteria require findings across categories but not necessarily all features 1
• Do not confuse CRPS with acute compartment syndrome, which presents with pain out of proportion but requires urgent fasciotomy and shows different clinical progression 5
• Some signs previously thought crucial (such as skin temperature differences >1°C) are less common than historically assumed 6
• CRPS does not demonstrate a placebo response except at very early time points (15-30 minutes), which helps distinguish it from other pain syndromes 1

High-Risk Clinical Contexts

• History of limb trauma or surgery is the typical trigger 1, 3
• Females have substantially higher risk than males 3
• Workplace accidents are a well-recognized cause 3
• Most commonly affects distal limbs following injury 3

Emerging Objective Diagnostic Tools

• Quantitative sensory testing (QST) may support diagnosis in complex cases 4
• Intraepidermal nerve fiber density (IENFD) assessment via skin biopsy 4
• Functional MRI showing brain plasticity changes 4
• Serum biomarkers of neuroinflammation (investigational) 4