1. Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul, Korea.
2. Brain Korea 21 PLUS Project for Medical Science, Yonsei University College of Medicine, Seoul, Korea.
3. Department of Otorhinolaryngology-Head and Neck Surgery, Soonchunhyang University College of Medicine, Seoul, Korea.
4. Department of Pathology, Yonsei University College of Medicine, Seoul, Korea.