Role of MR Imaging in Complex Regional Pain Syndrome Revisited

Purpose: To apply a set of magnetic resonance imaging (MRI) criteria to patients with suspected complex regional pain syndrome (CRPS) of the foot to evaluate the diagnostic potential of MRI.

Methods and Materials: A retrospective health-record search was conducted. Fifty patients with initially suspected CRPS of the foot were included (37 women [51 ± 13 years] and 13 men [44 ± 15 years]). All patients underwent MRI including gadolinium application and dynamic magnetic resonance angiography. Two radiologists assessed MRI: skin (thickness, enhancement, subcutaneous edema); bone (number of bones with edema, bone marrow edema pattern, subcortical enhancement, periosteal enhancement); and soft tissue (muscle edema, angiography perfusion pattern, joint effusion). Final diagnosis was CRPS (Budapest criteria) or non-CRPS. MRI parameters were compared between CRPS patients and non-CRPS patients.

Results: CRPS was diagnosed in 22 of 50 patients (44%) and non-CRPS in 28 of 50 patients (56%). Skin thickness (1.9 ± 0.5 mm versus 1.7 ± 0.3 mm; p = 0.399), enhancement, and subcutaneous edema showed no differences between CRPS and non-CRPS patients. Bone marrow edema presence and pattern were not different between groups. Up to 50% of CRPS patients showed no bone marrow edema. Subcortical enhancement and periosteal enhancement were not different between groups. For reader 1, muscle edema score was higher in the non-CRPS group compared with the CRPS group (0.1 ± 0.2 versus 0.6 ± 1.0; p = 0.008) but not different for reader 2 (0.1 ± 0.5 versus 0.2 ± 0.8; p = 0.819). Perfusion pattern was more extensive in non-CRPS patients for reader 1 (p = 0.048) but not for reader 2 (p = 0.157). Joint effusions showed no difference between groups.

Conclusion: MRI cannot distinguish between CRPS and non-CRPS. CRPS remains a clinical diagnosis. The role of MRI lies in excluding differential diagnoses.

Fig. 1 Example of dynamic magnetic resonance angiography in complex regional pain syndrome (CRPS) and non-CRPS patient, showing soft tissue enhancement in both cases.