[1] Kuopio Univ Hosp, Dept Neurosurg, Kuopio 70211, Finland
[2] Kuopio Univ Hosp, Dept Clin Radiol, Kuopio 70211, Finland
[3] Kuopio Univ Hosp, Dept Intens Care, Kuopio 70211, Finland
[4] Univ Helsinki, Cent Hosp, Dept Neurosurg, Helsinki, Finland
[5] Macquarie Univ, Dalcross Hosp, Australian Sch Adv Med, Sydney, NSW 2109, Australia