[1] Liverpool Hosp, Dept Neurosurg, Sydney, NSW 2170, Australia
[2] Penn State Univ, Hershey Med Ctr, Dept Neurosurg Hershey, University Pk, PA 16802 USA
[3] Fremantle Hosp, Dept Clin Neurophysiol, Perth, WA, Australia
[4] Sir Charles Gairdner Hosp, Interhosp Neurosurg Serv, Perth, WA, Australia
[5] Univ Western Australia, Perth, WA 6009, Australia