1. Department of Neurosurgery, Kyung Hee University Medical Center, Seoul 02447, Republic of Korea
2. Department of Neurosurgery, Kyung Hee University College of Medicine, Seoul 02447, Republic of Korea
3. Department of Urology, National Police Hospital, Seoul 05715, Republic of Korea
4. Department of Neurosurgery, School of Medicine, Inje University Busan Paik Hospital, 75 Bokji-ro, Busanjin-gu, Busan 47392, Republic of Korea