1. Department of Radiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
2. Department of Otolaryngology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
3. Department of Neurological Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States
4. Department of Neurosurgery, Medical College of Wisconsin, De Pere, Wisconsin, United States
5. Department of Neurosurgery Stanford University Medical Center, Stanford, California, United States