Complex Regional Pain Syndrome or Limb Pain: A Plea for a Critical Approach

Abstract

Most frequently, complex regional pain syndrome (CRPS) develops after a trauma and affects distal parts of the limbs. Early recognition and initiation of adequate treatment is crucial for a favorable outcome. On the other hand, misdiagnosing other disorders as CRPS is detrimental because more appropriate treatment may be withheld from the patients. Despite intensive research, a specific biomarker or paraclinical measure for CRPS diagnosis is still lacking. Instead, clinical criteria approved by the International Association for the Study of Pain (IASP) and latest adapted in 2019 are central for diagnosing CPRS. Thus, the CRPS diagnosis remains challenging with the risk of a "deliberate diagnosis" for unexplained pain, while at the same time a delayed CRPS diagnosis prevents early treatment and full recovery. CRPS is a diagnosis of exclusion. To clinically diagnose CRPS, a vigorous exclusion of "other diseases that would better explain the signs and symptoms" are needed before the patients should be referred to tertiary centers for specific pain treatment. We highlight red flags that suggest "non-CRPS" limb pain despite clinical similarity to CRPS. Clinical and neurological examination and paraclinical evaluation of a probably CRPS patient are summarized. Finally, we pinpoint common differential diagnoses for CRPS. This perspective might help CRPS researchers and caregivers to reach a correct diagnosis and choose the right treatment, regardless whether for CRPS mimics or CRPS itself.

Keywords: diagnostic criteria; differential diagnoses; misdiagnoses; paraclinical evaluation.

Figure 1

Thermography depicting the cold skin after forearm injury refined to the ulnar nerve innervation territory (5th and ulnar half of the 4th finger). The patient suffered from typical neuropathic pain which could be treated successfully with anticonvulsants. The correct diagnosis is posttraumatic neuralgia of the ulnar nerve.

Figure 2

Example of spontaneous “CRPS” which in fact was a paraneoplastic condition called palmar fasciitis polyarthritis syndrome (PAPS; probably immune-mediated), which developed before the cancer was recognized in a 75-year-old woman with ovarian cancer. Marie I, Cailleux N, Roca F, Benhamou Y, Scotte M, Levesque H. Palmar fasciitis and polyarthritis syndrome. QJM. 2010;103(9):703–704. by permission of Oxford University Press.

Figure 3

Example of a toxic-induced skin ulcer. This painful extremity is red, swollen and has extensive hair growth, and the proximal skin was dry. The CRPS criteria 1–3 would be fulfilled but notice that the distal fingers have normal color and are without edema. The lack of a distal generalization of the symptoms speaks against CRPS. The obvious etiology in this case is a skin ulcer which developed after erroneous subcutaneous infusion of mitoxantrone and was finally cured with skin transplantation. In less obvious cases, when the phenomenon of distal generalization is ignored, such a constellation of symptoms could lead to a false CRPS diagnosis.