1. Department of Otorhinolaryngology-Head and Neck Surgery, Samsung Changwon Hospital, Sungkyunkwan University School of Medicine, Changwon, Korea.
2. Department of Otorhinolaryngology-Head and Neck Surgery, Samsung Seoul Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea.
3. Department of Otorhinolaryngology-Head and Neck Surgery, St. Vincent's Hospital, The Catholic University of Korea, College of Medicine, Seoul, Korea.