1. Department of Neurosurgery, Louisiana State University Health Sciences Center, Shreveport, Louisiana;
2. Division of Occupational and Environmental Medicine, Department of Emergency Medicine, The University of Pennsylvania, Philadelphia, Pennsylvania;
3. Department of Aerospace Medicine, U.S. Navy, Airborne Command & Control and Logistics Wing, Point Mugu, California; and
4. Department of Neurosurgery, University of South Alabama, Mobile, Alabama