How to Diagnose Complex Regional Pain Syndrome
CRPS is primarily a clinical diagnosis based on the Budapest Criteria, requiring continuous pain disproportionate to the inciting event for at least 12 months to be considered chronic, with confirmation through three-phase bone scintigraphy when imaging is needed. 1
Clinical Diagnostic Criteria
Use the Budapest Criteria as your diagnostic framework, which requires all of the following 1, 2:
Continuous pain disproportionate to any inciting event that is excruciating, burning in quality, and gradually increases in intensity 1, 3
At least one symptom in three of four categories:
At least one sign in two or more categories on examination 1, 2
No other diagnosis better explains the signs and symptoms 1, 2
Key Clinical Features to Document
Pain Characteristics
- Pain that spreads within the affected limb and sometimes to the contralateral limb 1, 3
- Allodynia (pain with light touch) and hyperalgesia (exaggerated pain response) are hallmark features 1
- Pain typically develops 4-6 weeks after direct trauma, injury, or surgery 4
Autonomic Dysfunction
- Temperature dysregulation with skin temperature differences (though differences >1°C are less common than previously assumed) 5
- Skin color changes (mottled, red, or pale appearance) 1, 3
- Abnormal sweating patterns (increased or decreased) 1
Motor Impairment
- Functional limb weakness appearing disproportionate to initial injury 1, 3
- Decreased active range of motion 1
- Difficulty with weight-bearing, transfers, and using the limb for stabilization 3
Trophic Changes
- Hair loss at the affected site 1, 3
- Tissue changes and skin discoloration 1, 3
- Skin and tissue atrophy in chronic cases 2
Diagnostic Testing
When to Order Imaging
Three-phase bone scintigraphy is the most useful imaging modality when objective confirmation is needed, with sensitivity of 78% and specificity of 88% 6, 1, 7. Order this test when 6, 1:
- Clinical diagnosis is uncertain
- You need to rule out CRPS in patients with chronic post-traumatic pain without clear etiology
- High specificity is needed to exclude CRPS
MRI has limited utility as a screening test with higher specificity (91%) but much lower sensitivity (35%), making it unsuitable for initial diagnostic workup 1. However, MRI may be useful in CRPS Type II to visualize nerve lesions and denervation changes 1.
Distinguishing CRPS Type I vs Type II
- Type I (formerly reflex sympathetic dystrophy): No identifiable nerve injury despite thorough clinical evaluation 1, 7
- Type II: Confirmed nerve injury documented through clinical examination or diagnostic testing 1, 7
- Treatment is identical for both types 4
Chronic CRPS Diagnostic Considerations
For symptoms persisting ≥12 months, apply chronic-specific criteria 1, 2:
- Fulfillment of Budapest Criteria for at least 12 months 2
- At least three of five specific historical features (disease duration, clinical progression patterns) 2
- Asymmetric limb findings with musculoskeletal dystrophy 2
- Optional: intraepidermal nerve fiber density testing or imaging evidence of regional bone demineralization 2
Common Diagnostic Pitfalls
Avoid these errors:
- Assuming temperature differences >1°C must be present—this sign is less common than traditionally thought 5
- Failing to recognize that CRPS is a diagnosis of exclusion requiring ruling out other neurological causes of weakness 3
- Missing CRPS in diabetic patients who may have severe tissue loss but minimal pain due to concomitant neuropathy 3
- Over-relying on imaging when clinical criteria are sufficient 1, 2
- Delaying diagnosis waiting for "classic" presentation—early detection is critical for treatment success 8, 4
Specialist Consultation
Refer to pain specialty consultation when 6:
- Diagnosis remains uncertain after initial evaluation
- Complex pain syndrome requires assistance with both diagnosis and management
- Patient needs multimodal treatment coordination