1. From the Stroke Research Group (D.J.H.M., A.C.P., M.M.B.), Institute of Neurology, University College London; the University Department of Clinical Neurosciences (D.J.H.M.), Royal Free and University College Medical School; the Departments of Neuroradiology (A.C.), and Neurology (A.C.P.), St. George’s Hospital, London; and the Department of Health Sciences (J.M.B.), University of York, Heslington, York, UK