1. Department of Neurosurgery, Division of Biostatistics and Bioinformatics, University of Maryland School of Medicine, Baltimore, Maryland, USA.
2. R. Adams Cowley Shock Trauma Center, and Division of Biostatistics and Bioinformatics, University of Maryland School of Medicine, Baltimore, Maryland, USA.
3. Department of Epidemiology and Public Health, Division of Biostatistics and Bioinformatics, University of Maryland School of Medicine, Baltimore, Maryland, USA.
4. Department of Neurosurgery, Walter Reed National Military Medical Center, Bethesda, Maryland, USA.