1. Department of Neurosurgery, University of Tennessee Health Sciences/Semmes-Murphey Clinic, Memphis, Tennessee, USA
2. Department of Radiology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
3. Department of Neurosurgery, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin, USA
4. Inland Neurosurgery, Spokane, Washington, USA
5. Department of Neurosurgery, University of Minnesota, Minneapolis, Minnesota, USA