Jamarri Lawrence (IMAGE) Medical University of South Carolina Caption Eight-year-old Jamarri Lawrence has a transcranial Doppler exam to gauge whether he's at risk of having a stroke. Credit Sarah Pack Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.