1. Department of Neurosurgery, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
2. Department of Neurosurgery, Yeungnam University Hospital, Yeungnam Universtiy College of Medicine, Daegu, Korea.
3. Department of Neurosurgery, Soonchunhyang University Cheonan Hospital, College of Medicine, Soonchunhyang University, Cheonan, Korea.