Ai Huey Tan1, Shen-Yang Lim1, Rong Xiang Ng2. 1. Division of Neurology and the Mah Pooi Soo and Tan Chin Nam Centre for Parkinson's and Related Disorders, University of Malaya, Kuala Lumpur, Malaysia. 2. Department of Medicine, University of Malaya Medical Centre, Kuala Lumpur, Malaysia.