1. Department of Otorhinolaryngology-Head and Neck Surgery, Hallym University College of Medicine, Kangnam Sacred-Heart Hospital, Seoul, Korea.
2. Department of Otolaryngology-Head and Neck Surgery, Korea University College of Medicine, Seoul, Korea.
3. Department of Otolaryngology-Head and Neck Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
4. Department of Otolaryngology-Head and Neck Surgery, Seoul National University College of Medicine, Seoul, Korea.
5. Department of Biostatistics, College of Medicine, Catholic University of Korea, Seoul, Korea.
6. Division of Speech Pathology and Audiology, Hallym University College of Natural Sciences, Chuncheon, Korea.
7. Department of Otolaryngology-Head and Neck Surgery, School of Medicine, Hanyang University, Seoul, Korea.