What are the diagnosis criteria for Complex Regional Pain Syndrome (CRPS)?

Diagnostic Criteria for Complex Regional Pain Syndrome (CRPS)

The diagnosis of CRPS is primarily clinical, based on the Budapest diagnostic criteria, which include specific patterns of pain, sensory, vasomotor, sudomotor/edema, and motor/trophic changes that cannot be explained by other conditions. 1

Budapest Diagnostic Criteria

Clinical Diagnostic Criteria (all must be met):

1. Continuing pain disproportionate to any inciting event

2. At least one symptom in each of the following categories:

   • Sensory: Hyperesthesia and/or allodynia
   • Vasomotor: Temperature asymmetry, skin color changes, and/or skin color asymmetry
   • Sudomotor/Edema: Edema, sweating changes, and/or sweating asymmetry
   • Motor/Trophic: Decreased range of motion, motor dysfunction, and/or trophic changes (hair, nail, skin)

3. At least one sign at time of evaluation in two or more of the following categories:

   • Sensory: Evidence of hyperalgesia (to pinprick) and/or allodynia (to light touch)
   • Vasomotor: Evidence of temperature asymmetry, skin color changes, and/or asymmetry
   • Sudomotor/Edema: Evidence of edema, sweating changes, and/or sweating asymmetry
   • Motor/Trophic: Evidence of decreased range of motion, motor dysfunction, and/or trophic changes

4. No other diagnosis better explains the signs and symptoms

CRPS Classification

CRPS is subdivided into two types:

• CRPS Type I: Occurs without identifiable nerve injury (formerly called reflex sympathetic dystrophy)
• CRPS Type II: Occurs after damage to a peripheral nerve (formerly called causalgia) 2

Clinical Presentation

CRPS typically presents with:

• Pain described as excruciating and made worse by touch or stimulation
• Pain that gradually increases in intensity and size in the affected limb
• Potential spread to the contralateral limb
• Associated hair loss, tissue changes, and skin discoloration at the pain site 2
• Pain that usually follows an injury, often minor 2

Diagnostic Testing

While diagnosis is primarily clinical, certain tests may help support the diagnosis or rule out other conditions:

1. Three-phase bone scan:

   • Highest diagnostic utility with pooled sensitivity of 78% and specificity of 88%
   • May be useful to rule out CRPS Type I due to high negative predictive value (88%) 2
   • Shows increased periarticular uptake in distal joints 2

2. MRI:

   • High specificity (91%) but low sensitivity (35%) for CRPS Type I
   • More useful for CRPS Type II due to ability to visualize nerves and detect muscle denervation 2
   • Not recommended as a screening test due to low sensitivity 2

3. Ultrasound:

   • May show increased power Doppler flow in affected extremities
   • Sensitivity of 73% and specificity of 92% for CRPS Type I 2
   • High-resolution US may be useful in CRPS Type II for nerve assessment 2

Common Diagnostic Pitfalls

1. Delayed diagnosis: Early recognition is critical for better outcomes and minimizing permanent functional loss 3

2. Over-diagnosis: Lack of standardized diagnostic approaches has led to over-diagnosis, excessive pharmacotherapy, and unnecessary surgical interventions 4

3. Failure to exclude other conditions: Conditions with similar presentations must be ruled out, including neuropathic pain syndromes, vascular disorders, and inflammatory conditions

4. Relying solely on imaging: Remember that imaging studies should support, not replace, clinical diagnosis based on the Budapest criteria

5. Not recognizing motor and trophic changes: These form a distinct component of CRPS that is important for diagnosis and may predict response to sympathetic blocks 5

Diagnostic Algorithm

1. Assess for continuing pain disproportionate to inciting event
2. Document symptoms in all four categories (sensory, vasomotor, sudomotor/edema, motor/trophic)
3. Perform clinical examination to identify signs in at least two categories
4. Consider supportive testing if diagnosis is uncertain:
   • Three-phase bone scan (highest combined sensitivity/specificity)
   • MRI (if nerve injury suspected - CRPS Type II)
   • Ultrasound (if available with expertise in neuromuscular imaging)
5. Rule out alternative diagnoses that could better explain symptoms
6. Apply Budapest criteria to confirm diagnosis

Early diagnosis and treatment are essential as CRPS can lead to permanent impairment and disability if symptoms persist 3. The diagnostic approach should be thorough but efficient to facilitate prompt intervention.