1 Department of Neurosurgery, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA.
2 Section of Pediatric Neurosurgery, Oklahoma Children's Hospital, Department of Neurosurgery, University of Oklahoma School of Medicine, Oklahoma City, Oklahoma, USA.
3 Division of Pediatric Neurosurgery, Ann and Robert H. Lurie Children's Hospital, Chicago, Illinois, USA.
4 Department of Neurosurgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA.