1. Department of Neurology University of Pennsylvania Perelman School of Medicine Philadelphia Pennsylvania USA
2. Department of Neurology University of Mississippi Medical Center Jackson Mississippi USA
3. Department of Radiology Mayo Clinic Rochester Minnesota USA
4. Department of Epidemiology University of North Carolina at Chapel Hill Chapel Hill North Carolina USA
5. National Institute of Neurological Disorders and Stroke Intramural Research Program Bethesda Maryland USA
6. Department of Biostatistics, Epidemiology, and Informatics University of Pennsylvania Perelman School of Medicine Philadelphia Pennsylvania USA
7. Department of Neurology Johns Hopkins University School of Medicine Baltimore Maryland USA