1. Department of Clinical Neurosciences (M.G., J.M.O., A.G., M.M.), University of Calgary, Canada.
2. Department of Radiology (M.G.), University of Calgary, Canada.
3. Department of Neuroradiology, University Hospital Basel, Switzerland (J.M.O.).
4. Department of Neurology, Medical University of Vienna, Austria (M.M.).
5. Department of Neurology, Beth Israel Deaconess Medical Center, Boston, MA (M.F.).