1 Division of Neurosurgery, University of Toronto, Toronto Western Hospital, 399 Bathurst Street, West Wing 4-427, Toronto, Ontario, M5T 2S8 Canada. Electronic address: jetan.badhiwala@mail.utoronto.ca.
2 Division of Neurosurgery, University of Toronto, Toronto Western Hospital, 399 Bathurst Street, West Wing 4-427, Toronto, Ontario, M5T 2S8 Canada.
3 Division of Neurosurgery and Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada.