[1] Univ Malaya, Neurol Unit, Dept Med, Kuala Lumpur, Malaysia
[2] Int Med Univ, Dept Life Sci, Kuala Lumpur, Malaysia
[3] Univ Malaya, Inst Biol Sci, Kuala Lumpur, Malaysia
[4] Univ Malaya, Dept Med Microbiol, Kuala Lumpur, Malaysia
[5] Univ Malaya, Dept Med, Gastroenterol Unit, Kuala Lumpur, Malaysia
[6] Toronto Western Hosp, Morton & Gloria Shulman Movement Disorders Clin, Toronto, ON, Canada
[7] Toronto Western Hosp, Edmond J Safra Program Parkinsons Dis, Toronto, ON, Canada