[1] Australasian Movement Disorder & Pain Surg Clin, Melbourne, Vic 3004, Australia
[2] Radcliffe Infirm, Dept Neurosurg, Oxford OX2 6HE, England
[3] Charing Cross Hosp, Dept Neurosurg, London, England
[4] Univ London Imperial Coll Sci & Technol, Div Neurosci, London, England
[5] Radcliffe Infirm, Dept Anaesthesia, Oxford OX2 6HE, England
[6] Alfred Melbourne, Dept Neurosurg, Melbourne, Vic, Australia
[7] Monash Univ, Dept Surg, Melbourne, Vic 3004, Australia
[8] Melbourne Neurosurg, Melbourne, Vic, Australia