1. Department of Neurosurgery Washington University St. Louis St. Louis MO USA
2. Department of Neurosurgery Stanford University Palo Alto CA USA
3. Department of Neurosurgery Vanderbilt University Medical Center Nashville TN USA
4. Department of Neurosurgery University of Toronto Toronto Ontario Canada
5. Data Coordinating Center University of Utah Salt Lake City UT USA
6. Department of Clinical Neurosciences University of Calgary Calgary Alberta Canada
7. Department of Neurosurgery Baylor College of Medicine Houston TX USA
8. Department of Neurosurgery University of Alabama – Birmingham Birmingham AL USA
9. Department of Surgery University of British Columbia Vancouver British Columbia Canada
10. Department of Neurosurgery University of Pittsburgh Medical Center Pittsburgh PA USA
11. Department of Neurosurgery University of Utah Salt Lake City UT USA