[1] Rady Fac Hlth Sci, Dept Surg, Sect Neurosurg, Winnipeg, MB, Canada
[2] Shared Hlth Manitoba, Hlth Sci Ctr, Winnipeg, MB, Canada
[3] Rady Fac Hlth Sci, Dept Human Anat & Cell Sci, Winnipeg, MB, Canada
[4] Univ Cambridge, Dept Med, Div Anaesthesia, Cambridge, England
[5] Fac Engn, Biomed Engn, Winnipeg, MB, Canada
[6] Univ Manitoba, Ctr Aging, Winnipeg, MB, Canada