1. Neurocritical Care Unit; Addenbrooke's Hospital, Cambridge University, Box 1, Addenbrooke's Hospital, Cambridge University Hospitals Trust, Hills Road; Cambridge CB2 0QQ
2. Division of Neuroscience; University of Genoa; Genoa Italy
3. Division of Neurosurgery; Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge; Cambridge United Kingdom
4. Division of Critical Care Medicine; Department of Medicine, Vancouver General Hospital, University of British Columbia; Vancouver British Columbia