1. Division of Neurosurgery, Stroger Hospital of Cook County, and Department of Neurosurgery, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
2. Division of Neurosurgery, Stroger Hospital of Cook County, and Department of Neurosurgery, University of Illinois College of Medicine, Chicago, Illinois
3. Department of Neurosurgery, University of Illinois College of Medicine, Chicago, Illinois