1 Department of Medicine, National University Hospital and Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
2 Department of Neurology, Zydus Hospitals, Ahmedabad, Gujarat, India.
3 Department of Neurology, Ramkrishna Care Hospitals, Raipur, India.
4 Department of Medicine, National University Hospital and Yong Loo Lin School of Medicine, National University of Singapore, Singapore. Electronic address: drvijay@singnet.com.sg.