1. Department of Neurosurgery, University of Iowa Hospitals and Clinics, Iowa City, Iowa;
2. Departments of Neurosurgery and Radiology, University of Miami, Miami, Florida;
3. Department of Neurosurgery, Thomas Jefferson University, Philadelphia, Pennsylvania;
4. Department of Neurosurgery, Covenant Hospital, Waterloo, Iowa;
5. Department of Neurology, Neurosurgery, and Radiology, University of Iowa Hospitals and Clinics, Iowa City, Iowa;
6. Department of Neurosurgery, Mayo Clinic-Jacksonville, Jacksonville, Florida;
7. Department of Neurosurgery, University of Buffalo, Buffalo, New York;
8. Department of Neurosurgery and Neuroradiology, UT Southwestern Medical Center, Dallas, Texas; and
9. Department of Neurosurgery, Geisinger, Danville, Pennsylvania