1 Division of Neurology, Department of Medicine, National University Hospital, Singapore, Singapore.
2 Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
3 Division of Pediatric Genetics & Metabolism, Department of Pediatrics, Khoo Teck Puat-National University Children's Medical Institute, Singapore, Singapore.
4 Department of Diagnostic Imaging, National University Hospital, Singapore, Singapore.