1. Department of Radiology, Temple University School of Medicine, Philadelphia, PA, USA;
2. Department of Medicine, Temple University School of Medicine, Philadelphia, PA, USA;
3. Division of Clinical Neurology, University of Nottingham, Nottingham, UK;
4. Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA, USA;
5. Department of Neurology, Thomas Jefferson University, Philadelphia, PA, USA