1. Departments of Radiology and Neurological Surgery, Columbia University, Neurological Institute of New York, New York;
2. Departments of Radiology, Neurological Surgery, Neurology, and Anesthesiology, University of California, San Francisco, California;
3. Department of Neurosurgery, Barrow Neurological Institute, Phoenix, Arizona;
4. Cerebrovascular Center, Cleveland Clinic, Cleveland, Ohio; and
5. Department of Radiology, Harvard University and Massachusetts General Hospital, Boston, Massachusetts