[1] Univ Malaya, Div Neurol, Kuala Lumpur 50603, Malaysia
[2] Univ Malaya, Mah Pooi Soo & Tan Chin Nam Ctr Parkinsons & Rela, Kuala Lumpur 50603, Malaysia
[3] Univ Toronto, Toronto Western Hosp, Morton & Gloria Shulman Movement Disorders Ctr, Toronto, ON M5T 2S8, Canada
[4] Univ Toronto, Edmond J Safra Program Parkinsons Dis Res, Toronto, ON, Canada
[5] Malaysian Parkinsons Dis Assoc, Kuala Lumpur, Malaysia
[6] Univ Sains Islam Malaysia, Fac Med, Dept Med, Kuala Lumpur, Malaysia
[7] Univ Malaya, Inst Biol Sci, Kuala Lumpur 50603, Malaysia