1. Department of Neurosurgery, Yonsei University College of Medicine, Seoul, South Korea
2. Department of Neurosurgery, Spine Tumor Center and Special Cancer Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea
3. Department of Biostatistics, Seoul National University Boramae Medical Center, Seoul, South Korea
4. Department of Biostatistics, Robert Stempel College of Public Health and Social Work, FL International University, Miami, FL, USA
5. Department of Neurosurgery, Seoul National University Boramae Medical Center, Seoul, South Korea
6. Department of Neurosurgery, College of Medicine, Yeungnam University, Daegu, South Korea
7. Department of Neurosurgery, Seoul National University of Medicine, Seoul, South Korea