1. Departments of Neurosurgery and
2. Department of General Surgery, Mercy Medical Center, Des Moines, Iowa;
3. Department of Neurosurgery, University of Tokyo, Japan;
4. Department of Neurosurgery, University of Miami, Florida;
5. Department of Neurosurgery, Thomas Jefferson University, Philadelphia, Pennsylvania;
6. Department of Neurology, Mayo Clinic, Rochester, Minnesota;
7. Radiology, University of Iowa Hospitals and Clinics;
8. Department of Neurology, University of Iowa College of Medicine;
9. Department of Epidemiology, University of Iowa, Iowa City;
10. Department of Neurology, University of Cincinnati Medical Center, Cincinnati, Ohio; and
11. Department of Neurology, Medical University of South Carolina, Charleston, South Carolina