1. Division of Neurosurgery; Sunnybrook Hospital, University of Toronto; Ontario Canada
2. Department of Medical Imaging; Toronto Western Hospital and University Health Network, University of Toronto; Ontario Canada
3. Division of Neurosurgery; Toronto Western Hospital and University Health Network University of Toronto; Ontario Canada
4. Department of Neurosurgery; University Hospital Zürich; Switzerland
5. Department of Anesthesia; Toronto General Hospital and University Health Network University of Toronto; Ontario Canada
6. Department of Medical Imaging; Sunnybrook Hospital, University of Toronto; Ontario Canada