1. Departments of Pathology, The University of Iowa College of Medicine, Iowa City, Iowa
2. Department of Neurosurgery, Houston, Texas
3. West Virginia University Medical School, Morgantown, West Virginia; Department of Medicine, Houston, Texas
4. Preventive Medicine, The University of Iowa College of Medicine, Iowa City, Iowa
5. Baylor College of Medicine, Houston, Texas; Department of Pediatrics, Houston, Texas
6. University of Texas Medical School, Houston, Texas; and Texas Institute for Rehabilitation and Research, Houston, Texas
7. Division of Neurosurgery, Houston, Texas