Authors: M. Ross Bullock, MD, PhD, Department of Neurological Surgery, Virginia Commonwealth University Medical Center, Richmond, Virginia; Randall Chesnut, MD, Department of Neurological Surgery, University of Washington School of Medicine, Harborview Medical Center, Seattle, Washington; Jamshid Ghajar, MD, PhD, Department of Neurological Surgery, Weil Cornell Medical College of Cornell University, New York, New York; David Gordon, MD, Department of Neurological Surgery, Montefiore Medical Center, Bronx, New York; Roger Hartl, MD, Department of Neurological Surgery, Weil Cornell Medical College of Cornell University, New York, New York; David W. Newell, MD, Department of Neurological Surgery, Swedish Medical Center, Seattle, Washington; Franco Servadei, MD, Department of Neurological Surgery, M. Bufalini Hospital, Cesena, Italy; Beverly C. Walters, MD, MSc, Department of Neurological Surgery, New York University School of Medicine, New York, New York; Jack E. Wilberger, MD, Department of Neurological Surgery, Allegheny General Hospital, Pittsburgh, Pennsylvania