1. From FMRIB Centre (M.Z., C.M., C.F.B., S.M.S., P.M.M.), University Oxford, Oxford, UK; Departments of Neurology (J.S.D., P.S.) and Radiology (F.B.), VU University Medical Center, Amsterdam, Netherlands; Department of Radiology (S.A.R.B.R.), Leiden University Medical Center, Leiden, Netherlands.