1. Department of Orthopaedics and Sports Medicine, University of Washington, Seattle, Washington;
2. Department of Surgery, Division of Neurosurgery, University of Alabama at Birmingham, Alabama;
3. Department of Neurosurgery, Yale University, New Haven, Connecticut; and
4. Clarian Neuroscience Institute, Indianapolis Neurosurgical Group, and Indiana University Department of Neurosurgery, Indianapolis, Indiana