1. From the Department of Neurology, J. Philip Kistler Stroke Research Center, Massachusetts General Hospital, Boston (S.M.-R., A.C., M.E.G., S.M.G., A.V.)
2. Department of Radiology (S.v.R., A.M.v.O., M.W., J.v.d.G., M.v.B.)
3. Department of Neurology (G.T.), Leiden University Medical Center, the Netherlands.