1. Division of Neurosurgery, Walter Reed National Military Medical Center, Bethesda, Maryland, USA.
2. Kentucky Spinal Cord Injury Research Center, Louisville, Kentucky, USA.
3. Department of Neurosurgery, Houston Methodist Hospital, Houston, Texas, USA.
4. Department of Neurosurgery, Duke University, Durham, North Carolina, USA.
5. The Miami Project to Cure Paralysis, University of Miami, Miami, Florida, USA.
6. Neuroscience Institute. the Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
7. University of Maryland School of Medicine, Baltimore, Maryland, USA.
8. Thomas Jefferson University Hospital, Philadelphia, Pennsylvania, USA.
9. Division of Neurosurgery and Spine Program, Department of Surgery, University of Toronto, Toronto, Ontario, Canada.