Synovial effusion in reflex sympathetic dystrophy: an additional sign for diagnosis and staging

Purpose. To improve the present MRI criteria for diagnosis and staging of reflex sympathetic dystrophy (RSD) by including increased joint fluid as an additional MRI sign of RSD. Design and patients. One hundred and fourteen extremities (69 affected and 45 contralateral controls) in 57 consecutive patients with RSD were evaluated using a 1.5-T unit. T1- and T2-weighted pulse sequences, often with fat suppression, were used before and after administration of intravenous contrast enhancement (Cd). Following T2-weighted image digitization the volume of synovial fluid was measured with a computer model. Results. Effusions were detected in 61% of the extremities suspected of RSD and in 44% of the contralateral control joints. The mean fluid quantity measured in the symptomatic articulation was 201 mm(3). MRI diagnosis of RSD based on previously described criteria was done in 62% of the patients, yielding a sensitivity of 60%. Effusions were present in 79% of the false negative MRI cases. Retrospectively considering the presence of fluid as a potential positive criterion for RSD increases the sensitivity by 31% (to 91%). Conclusions. Joint effusions are probably associated with early stages of RSD. Adding effusion to the list of radiological criteria for RSD increases the sensitivity of MRI from 60% to 91%.