1. Department of Neurosurgery, Johns Hopkins University School of Medicine, Baltimore, Maryland;
2. Departments of Neurosurgery and Orthopaedic Surgery, University of Southern California Keck School of Medicine, Los Angeles, California;
3. Department of Neurosurgery, Thomas Jefferson University Hospitals, Philadelphia, Pennsylvania;
4. Department of Neurosurgery, University of Toronto, St. Michael’s Hospital, Toronto, Ontario, Canada;
5. Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, Wisconsin; and
6. Department of Neurosurgery, Lahey Hospital and Medical Center, Burlington, Massachusetts