Complex Regional Pain Syndrome MAKING A DIAGNOSIS

Learn about making a diagnosis for Complex Regional Pain Syndrome (CRPS). Understand the history of the diagnostic criteria and the modifications. Get insights on how to differentiate CRPS from other pain states.

History of Diagnostic Criteria for CRPS

The International Association for the Study of Pain (IASP) produced the new diagnostic entity of CRPS in 1994, which was descriptive and general based on a consensus. The criteria did not imply any etiology or pathology, including any direct role for the SNS, and the intention was to improve clinical communication and facilitate research.

However, the original criteria caused problems of overdiagnosis because of poor specificity and were inadequate in providing greater diagnostic or prognostic accuracy by observing more than one feature.

Validation and Modifications of Diagnostic Criteria

• Validation studies suggest that the original criteria are adequately sensitive within the context of a pain clinic; however, the criteria cause problems of overdiagnosis because of poor specificity.
• The criteria assume that any sign or symptom of vasomotor, sudomotor, and edema-related change is sufficient to justify the diagnosis, and there is no possibility of providing greater diagnostic or prognostic accuracy by observing more than one of these features.
• The failure to include motor or trophic signs and symptoms differentiates CRPS from other pain syndromes.
• The wording of the criteria permits diagnosis based solely on patient-reported historical symptoms, which may be inappropriate in the context of litigation.
• The Bruehl modification of the original IASP criteria applies to the diagnosis of CRPS within a pain clinic setting and is intended to differentiate CRPS from other causes of chronic pain within that setting. These criteria do not apply directly to the diagnosis of CRPS within the context of an orthopaedic practice.
• Atkins et al. proposed a set of diagnostic criteria for CRPS specifically in an orthopaedic context, which were derived empirically from a less formal but similar process to the IASP consensus approach. The criteria were designed as far as possible to be objective, but the patient’s veracity was assumed.

Therefore, it is critical to understand the differences between clinical and research diagnoses and to use the appropriate diagnostic criteria depending on the clinical circumstances.

Differentiating CRPS from Other Pain States

The diagnostic criteria for CRPS were modified to differentiate it from other causes of chronic pain within a pain clinic setting or an orthopaedic practice. To make a clinical diagnosis in an orthopaedic setting:

1. Excessive pain history: Compare pain perception with the opposite normal side. Excessive tenderness is found by squeezing digits in the affected part between thumb and fingers.
2. Sensory abnormalities: Demonstrate allodynia by fine touch and hyperalgesia using a pin. Examine hyperpathia by serial fine touch or pin prick.
3. Vasomotor instability: Inspect for temperature asymmetry and/or skin color changes and/or skin color asymmetry. Thermography can be used to quantitate temperature difference between the limbs.
4. Abnormal sweating: Excessive sweating is clinically obvious. In a doubtful case, the resistance to a biro or pencil gently stroked across the limb is useful.
5. Edema and swelling: Usually obvious on inspection. In the hand, it may be quantified by hand volume measurement, skinfold thickness, and digital circumference measurement.
6. Loss of joint mobility and atrophy: Loss of joint mobility is diagnosed by standard clinical examination. Atrophy will affect every tissue within the limb.
7. Bone changes: Radiographic appearances and bone scans can be used to investigate bone density.

Differentiating CRPS from other pain states is critical, and it is important to use the appropriate diagnostic criteria depending on the clinical context.