1. Department of Neurosurgery, Cleveland Clinic, Cleveland, Ohio;
2. Department of Neurosurgery, Yale University, New Haven, Connecticut;
3. Department of Neurosurgery, Wake Forest Medical Center, Winston-Salem, North Carolina;
4. Department of Neurosurgery, Washington University, St. Louis, Missouri;
5. Department of Neurosurgery, Kansas University, Kansas City, Kansas;
6. Department of Neurosurgery, Thomas Jefferson University, Philadelphia, Pennsylvania;
7. Carolina Neurosurgery and Spine, Charlotte, North Carolina;
8. Department of Radiology, University of Manitoba, Winnipeg, Manitoba, Canada; and
9. Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts