1. Mayo Clinic Alix School of Medicine, Scottsdale, Arizona, United States
2. University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
3. New York University School of Medicine, New York, New York, United States
4. Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States
5. Cooper Neurological Institute, Cooper Medical School of Rowan University, Camden, New Jersey, United States
6. Department of Neurological Surgery, Columbia University Medical Center, New York, New York, United States
7. Vagelos College of Physicians and Surgeons, Columbia University, New York, New York, United States