[1] Homerton Hosp, Dept Neurol, London E9 6SR, England
[2] St George Hosp, Dept Intens Care, Kogarah, NSW 2217, Australia
[3] St Bartholomews Hosp, Dept Intens Care, London EC1A 7BE, England
[4] Kings Coll Hosp London, Kings Neurosci Ctr, London SE5 9RS, England