1. Northwestern University, Feinberg School of Medicine, Chicago, IL, USA
2. Northwestern Memorial Hospital, Chicago, IL, USA
3. University of California Los Angeles, CA, USA
4. Toronto Western Hospital, Toronto, Ontario, Canada
5. Rush University Medical Center, Chicago, IL, USA
6. Brown University, Providence, RI, USA
7. Rhode Island Hospital, Providence, RI, USA
8. The Miriam Hospital, Providence, RI, USA
9. Norman Prince Neurosciences Institute, Providence, RI, USA
10. Jefferson Medical College, The Rothman Institute, Philadelphia, PA, USA
11. Mayo Clinic, Rochester, MN, USA
12. Kansas University Medical Center, Kansas City, KS, USA
13. Cleveland Clinic, Cleveland, OH, USA
14. University of Toronto, Toronto, Ontario, Canada
15. Washington University, St Louis, MO, USA
16. Cleveland Clinic Foundation, Cleveland, OH, USA
17. University Hospitals Case Medical Center, Cleveland, OH, USA
18. Duke University Medical Center, Durham, NC, USA
19. USC Spine Center, Los Angeles, CA, USA
20. University of Southern California, Los Angeles, CA, USA
21. Columbia University, New York, NY, USA
22. New York-Presbyterian/The Allen Hospital, New York, NY, USA