Division of Neurology, Department of Medicine, University of Toronto, Toronto, Ontario, Canada. Hurvitz Brain Sciences Program, Sunnybrook Research Institute, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada. Department of Medical Imaging, University of Toronto, Toronto, Ontario, Canada. Department of Clinical Neurosciences and Radiology, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada. Department of Community Health Sciences and Medicine, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada. Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada. Applied Health Research Centre, Li Ka Shing Knowledge Institute of St Michael's Hospital, Toronto, Ontario, Canada. Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio. Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio. Department of Neurosciences, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia. University of New South Wales, Prince of Wales Clinical School, Sydney, New South Wales, Australia. Ottawa Hospital Research Institute, University of Ottawa, Ottawa, Ontario, Canada. Division of Neurology, Department of Medicine, Dalhousie University, Halifax, Nova Scotia, Canada. Division of Cardiology, Department of Medicine, Medical University of South Carolina, Charleston. University of Ottawa, Ottawa, Ontario, Canada. Department of Neurology, University of Pennsylvania, Philadelphia. Department of Emergency Medicine, Washington University in St Louis, St Louis, Missouri. Department of Emergency Medicine, Massachusetts General Hospital, Boston. Department of Radiology, University of Cincinnati Academic Health Center, Cincinnati, Ohio. Mission Research Institute, Mission Health System, Asheville, North Carolina. Department of Neurology, University of Cincinnati Academic Health Center, Cincinnati, Ohio.