[1] Division of Neurosurgery,
[2] Toronto Western Hospital,undefined
[3] University of Toronto,undefined
[4] Toronto,undefined
[5] Ontario,undefined
[6] Canada e-mail: wallace@playfair.utoronto.ca Tel. + (4 16) 603–5428 Fax + (4 16) 603–52 98 2–427,undefined
[7] McLaughlin Pavilion,undefined
[8] Division of Neurosurgery,undefined
[9] Toronto Western Hospital,undefined
[10] 399 Bathurst Street. Toronto,undefined
[11] Ontario,undefined
[12] Canada,undefined
[13] M5 T 2S8,undefined