Effect of sympathetic block demonstrated by triple-phase bone scan.

The triple-phase bone scan is frequently used in the diagnosis of reflex sympathetic dystrophy although the etiology of the abnormal findings is not well established. This study evaluated the effect of increased blood flow secondary to sympathetic block on the triple-phase bone scan. In 15 reflex sympathetic dystrophy patients, all of whom had significant relief with sympathetic block, baseline and postsympathetic block bone scans were analyzed. There was a significant linear relationship between change in counts from baseline to postsympathetic block on the blood pool image and bone uptake image. As the blood pool and bone uptake counts increased, the likelihood of typical reflex sympathetic dystrophy findings on visual inspection also increased. These results strongly support the concept of increased vascular flow as the cause of increased periarticular uptake.