1. Department of Surgery, Division of Neurosurgery, University of Toronto, Toronto, Canada; Krembil Neuroscience Center and Spinal Program, Toronto Western Hospital, University Health Network, Toronto, Canada
2. Department of Pathology, Division of Neuropathology, University of Toronto, Toronto, Canada; Toronto Western Hospital, University Health Network, Toronto, Canada
3. Miami Project to Cure Paralysis, University of Miami, Miami, Florida
4. ICORD and Department of Physical Medicine & Rehabilitation, University of British Columbia, Vancouver, Canada; Department of Physical Medicine and Rehabilitation, University of Western Ontario, London, Canada