1. Department of Neurosurgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, and Department of Neurosurgery, St. Mary's Hospital, The Catholic University of Korea, Seoul, Korea
2. Departments of Neurosurgery and Radiology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
3. Department of Neurosurgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania
4. Department of Radiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas
5. Departments of Radiology and Neurosurgery, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas