1. Departments of Pediatric Neurosurgery, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
2. Children's Cancer Research Center, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
3. Children's Hospital of Philadelphia, and Departments of Neurosurgery, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
4. Departments of Pathology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania
5. Departments of Neurology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania