[1] Royal Perth Hosp, Dept Neurol, Stroke Unit, Perth, WA 6001, Australia
[2] Univ Western Australia, Sch Populat Hlth, Nedlands, WA 6009, Australia
[3] Univ Western Australia, Dept Med, Nedlands, WA 6009, Australia
[4] Univ London Imperial Coll Sci Technol & Med, London, England
[5] Univ Auckland, Clin Trial Res Unit, Auckland 1, New Zealand