1. From the Departments of Neurology (A.O., K.S., S.M.G., J.R.), Emergency Medicine (J.N.G., N.J.), and Radiology (J.M.R., M.H.L., J.E.D.A.), the Center for Human Genetic Research (J.R.), Massachusetts General Hospital, Boston; and the Calgary Stroke Program (E.E.S.), Department of Clinical Neurosciences, University of Calgary, Alberta, Canada.