Jae-Gu Cho1, Jeong-Soo Woo2. 1. Department of Otolaryngology-Head and Neck Surgery, Korea University College of Medicine, 80 Guro-dong, Guro-gu, Seoul, 152-703, South Korea. jgcho@korea.ac.kr. 2. Department of Otolaryngology-Head and Neck Surgery, Korea University College of Medicine, 80 Guro-dong, Guro-gu, Seoul, 152-703, South Korea.