1. Dalhousie University, Division of Neurosurgery, QEII Health Sciences Centre, Nova Scotia Health Authority, Halifax, Nova Scotia;
2. Dalhousie University, Department of Anesthesia, Pain Management & Perioperative Medicine, Halifax, Nova Scotia;
3. Department of Medicine, Department of Radiology, Health Sciences Centre, University of Manitoba, Winnipeg, Manitoba; and
4. Dalhousie University, Division of Diagnostic Radiology, Department of Diagnostic Radiology, QEII Health Sciences Centre, Nova Scotia Health Authority, Halifax, Nova Scotia, Canada