3-PHASE BONE-SCINTIGRAPHY - ASYMMETRIC PATTERNS IN THE UPPER EXTREMITIES OF ASYMPTOMATIC NORMALS AND REFLEX SYMPATHETIC DYSTROPHY PATIENTS

Three-phase Tc-99m MDP scans of 61 patients with asymptomatic upper ex tremities randomly mixed with 17 studies of patients previously diagno sed with reflex sympathetic dystrophy were blindly interpreted by thre e observers. Asymmetry in any of the phases was recorded and a final d iagnostic impression made. Thirteen of 17 reflux sympathetic dystrophy studies were rated abnormal by at least two observers. Mild to striki ng asymmetry was occasionally seen in all three phases in asymptomatic upper extremities. Twenty of 61 asymptomatic patients (33%) were rate d abnormal by at least one observer, and 5 of 61 studies (8%) were rat ed abnormal by all observers. Asymmetries in normal patients occurred more commonly in the earlier phases, while asymmetry in the delayed im ages was mild in all but one. Tightening the criteria to exclude mild asymmetry in delayed images resulted in unacceptably low sensitivity f or reflex sympathetic dystrophy (29%). Interobserver variability was m ost prominent in the flow and immediate images. In the diagnosis of re flex sympathetic dystrophy a greater reliance should be placed on the delayed images, which in themselves have an overall sensitivity of 94% . It is important, however, to recognize that occasional mild and rare moderate asymmetries in even the delayed images of normal individuals result in an overall lower specificity of 77%.