1. University of Toronto Vascular Malformation Study Group, Division of Neurosurgery, Department of Surgery, University of Toronto, Toronto, Ontario, Canada
2. Department of Internal Medicine, University of Toronto, Toronto, Ontario, Canada
3. Department of Health Administration and Medicine and Program in Clinical Epidemiology and Health Care Research (The Toronto Hospital Unit), University of Toronto, Toronto, Ontario, Canada
4. Department of Utilization Management, University of Toronto, Toronto, Ontario, Canada