1. Departments of Critical Care Medicine and Clinical Neurosciences, University of Calgary, Calgary, Canada
2. Division of Biostatistics and Epidemiology, Department of Public Health Sciences, University of Virginia, Charlottesville, Virginia
3. Department of Neurology, University of Virginia, Charlottesville, Virginia
4. Department of Neurological Surgery, University of Virginia, Charlottesville, Virginia
5. Departments of Neurology, Neurological Surgery, and Medicine, Feinberg School of Medicine, Northwestern University, Evanston, Illinois