1. From the Division of Neurosurgery, University of British Columbia, Vancouver, Canada (C.D., S.P., G.R., C.S.H., P.A.G.)
2. T.H. Chan School of Public Health, Harvard University, Boston, MA (C.D., H.S.P., F.N.)
3. Division of Otolaryngology – Head and Neck Surgery, University of British Columbia, Vancouver, Canada (H.S.P., E.P.)
4. Division of Vascular Surgery, McMaster University, Hamilton, Canada (F.N.).