1. Department of Neurosurgery, Johns Hopkins School of Medicine, Baltimore, Maryland;
2. Department of Neurology, University of Texas Southwestern Medical Center, Dallas, Texas;
3. Division of Interventional Neuroradiology, Johns Hopkins School of Medicine, Baltimore, Maryland;
4. Department of Neurosurgery, Northwestern University, Chicago, Illinois; and
5. Department of Vascular Surgery and Endovascular Therapy, Johns Hopkins School of Medicine, Baltimore, Maryland