1. Department of Neurologic Surgery, Regions Hospital, St. Paul, MN, USA;
2. Department of Orthopedics, University of Minnesota, Minneapolis, MN, USA;
3. National Brain Aneurysm & Tumor Center, Department of Neurosurgery, United Hospital, Twin Cities, MN, USA;
4. Department of Neuroscience, University of Southern California, Los Angeles, CA, USA