[1] Univ Witten Herdecke, Sch Med, Witten, Germany
[2] Natl Univ Singapore Hosp, Univ Surg Cluster, Div Neurosurg, Singapore 119074, Singapore
[3] Natl Univ Singapore Hosp, Dept Diagnost Radiol, Singapore 119074, Singapore
[4] Natl Inst Neurosci, Dept Neuroradiol, Singapore, Singapore
[5] Univ New S Wales, Prince Wales Hosp, Ctr Minimally Invas, Sydney, NSW, Australia