1. Department of Neurosurgery, University of Oklahoma, Norman, Oklahoma, USA;
2. Department of Neurosurgery, University of Pennsylvania, Philadelphia, Pennsylvania, USA;
3. Atlantic Neurosurgical Specialists, Morristown, New Jersey, USA;
4. Department of Neurosurgery, UPMC, Pittsburgh, Pennsylvania, USA;
5. Department of Neurosurgery, University of Texas San Antonio, San Antonio, Texas, USA;
6. Department of Neurosurgery, Kaiser Permanente Orange County Anaheim Medical Center, Anaheim, California, USA;
7. Department of Neurological Surgery, Germans Trias i Pujol University Hospital, Universidad Autónoma, Barcelona, Spain;
8. Department of Neurological Surgery, UCSF, San Francisco, California, USA