1. Department of Neurological Surgery, Vanderbilt University Medical Center, Nashville, Tennessee, USA;
2. Current Affiliation: Department of Orthopedic Surgery, Daniel and Jane Och Spine Hospital, Columbia University Medical Center, New York, New York, USA;
3. Current Affiliation: Department of Neurological Surgery, Weill Cornell Medical Center, New York, New York, USA;
4. School of Medicine, Vanderbilt University, Nashville, Tennessee, USA;
5. §Current affiliation: TriStar Centennial Medical Center, Nashville, Tennessee, USA;
6. Current Affiliation: Department of Neurological Surgery, Children's of Alabama, University of Alabama at Birmingham, Birmingham, Alabama, USA