1. Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, Maryland.
2. Department of Orthopedics, University of Maryland School of Medicine, Baltimore, Maryland.
3. Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, Maryland.
4. Department of Biomedical Engineering, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
5. Department of Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland.