MRI findings in reflex sympathetic dystrophy of the foot

Purpose : To describe the MRI findings of reflex sympathetic dystrophy of t he foot and ankle. Methods: Retrospective study of 50 patients with reflex sympathetic dystrop hy of the foot (5 with the cold form, and 45 with the warm form) diagnosed based on clinical and scintigraphic findings. All patients underwent MR ima ging. The MRI findings were correlated with the clinical and scintigraphic findings. Results : Patients with the cold form of reflex sympathetic dystrophy had n o abnormality of signal at MR imaging. All patients with the warm form of r eflex sympathetic dystrophy showed periarticular marrow edema at MR, typica lly involving more than one bone (mean of 4). Other findings were inconstan t: soft tissue edema, joint effusion, and rarely, subchondral band of low T 1W signal intensity of unclear etiology. Conclusion : MR imaging, including fat-suppressed T2W or STIR images and no ncontrast T1W images, is helpful in patients with the warm or acute form of reflex sympathetic dystrophy of the foot, In patients with the cold form, MR imaging is helpful to exclude another underlying etiology for the sympto ms and identify patients with the warm form of the process.