1 Department of Neuroradiology, Karolinska University Hospital, Solna, Sweden.
2 Department of Clinical Neuroscience, Neurology, Karolinska Institute, Stockholm, Sweden.
3 Division of Neurology, Department of Medicine, National University Health System, National University Health System and Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
4 Department of Radiology, New England Center for Stroke Research, University of Massachusetts Medical School, Worcester, Massachusetts, USA.