Complex Regional Pain Syndrome in Emergency Medicine Workup

Updated: Sep 07, 2023
  • Author: Marcella L Ruffo, MD; Chief Editor: Andrew K Chang, MD, MS  more...
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Laboratory Studies

A single, reliable, sensitive, and specific diagnostic test for complex regional pain syndrome (CRPS) is not available.

Quantitative sensory testing and quantitative sudomotor axon reflex test (QSART) may be performed to look for sensory and sweating abnormalities. [37]

And as noted above, experts agree that diagnostic studies are not necessary to make the diagnosis. [29, 30]


Imaging Studies

Although not required for diagnosis, these studies have been advocated for a variety of reasons.

  • Three-phase bone scan and gadolinium magnetic resonance imaging (MRI) have been used to diagnose and stage the disease.

  • Standard radiographic findings are normal in as many as 30% of patients. However, they may show osteoporosis as soon as 3-5 weeks of onset.

  • Laser Doppler flow studies have been used to monitor background vasomotor control.

  • A cold pressor test performed in conjunction with thermographic imaging observes vasoconstrictor response.

  • Functional MRI (fMRI) has been used to demonstrate that allodynic stimulation produces objective findings. [37]

  • Magnetic resonance neurography (MRN) can be used to evaluate specific areas of nerve damage. 

  • Structural MRI may be useful for the measurement of gray matter volume, which was directly correlated to pain intensity in one study [38]

  • Triple-phase bone scans with dye can evaluate excess bone resorption



Some authors believe that the best diagnostic approach for complex regional pain syndrome (CRPS) involves use of differential neural blockade. In those with sympathetically mediated pain (as opposed to those whose pain is sympathetically independent), response to neural blockade may help guide medical therapy.

  • For cases involving an upper extremity, a stellate ganglion block may aid the diagnostic process and may be therapeutic. However, failure to relieve pain does not eliminate the diagnosis. [5, 33]

  • Differential blockade has been performed using Bier blocks with a variety of agents, including local anesthetics, bretylium, steroids, ketorolac, reserpine, and guanethidine and clonidine. [33, 39]

  • The rationale for selective neural blockade is to interrupt stimulation to the sympathetic nervous system. Again, this is effective only in those whose pain is sympathetically dependent. [33]