Affiliation: | (1) Division of Neurosurgery, Toronto Western Hospital, University of Toronto, Toronto, Ontario, Canada e-mail: wallace@playfair.utoronto.ca Tel. + (4 16) 603–5428 Fax + (4 16) 603–52 98 2–427, McLaughlin Pavilion, Division of Neurosurgery, Toronto Western Hospital, 399 Bathurst Street. Toronto, Ontario, Canada, M5 T 2S8, CA |