[1] Univ Amsterdam, Acad Med Ctr, Dept Neurol, NL-1105 AZ Amsterdam, Netherlands
[2] Free Univ Amsterdam, Acad Hosp, Dept Neurosurg, Amsterdam, Netherlands
[3] Free Univ Amsterdam, Acad Hosp, Dept Clin Epidemiol & Biostat, Amsterdam, Netherlands
[4] Slotervaart Gen Hosp, Dept Neurosurg, Amsterdam, Netherlands