The effect of transfusion therapy on the risk for new silent infarct or stroke in children with sickle cell anemia and abnormal transcranial Doppler (TCD) ultrasonography was determined at the University of Miami, FL, and other centers in the STOP trial (Stroke Prevention in Sickle Cell Anemia). One hundred thirty subjects with elevated TCD ultrasonographic velocity, including 47 (37%) with previous silent infarcts, were randomized to receive long-term transfusion therapy or standard care. MRIs were performed initially, annually, and when indicated by clinical symptoms. Among children with previous silent infarcts, standard care was associated with a significantly increased risk of new silent infarcts or stroke when compared to those receiving transfusion therapy. MRI lesions at baseline carried an increased risk of stroke or new silent lesions in standard care patients. Transfusion therapy lowers the risk for new silent infarct or stroke in children with both abnormal cerebral artery velocity and silent infarct. Subjects with both abnormalities who are not transfused are at increased risk of new silent infarct or stroke when compared to those with normal initial MRI. An abnormal initial MRI indicates the need for TCD screening and probable transfusion therapy. Elevated TCD velocity indicates the need for MRI to exclude silent infarcts. 
COMMENT. Children with sickle cell anemia who have elevated TCD ultrasonographic velocities account for only 10% of patients. However, most strokes in these patients are associated with an abnormal TCD, and the test is important particularly in those with MRI evidence of previous silent infarct. Patients with both abnormal TCD and MRI are candidates for transfusion therapy. Studies are recommended to determine the need for transfusion therapy in children with normal TCD and abnormal baseline MRI.