1. Department of Otolaryngology, The Women and Children's Hospital of Qingdao, Qingdao, Shandong 266033, P.R. China
2. Department of Otolaryngology, The Affiliated Hospital of Qingdao University, Qingdao, Shandong 266033, P.R. China
3. Department of Medicine, The Women and Children's Hospital of Qingdao, Qingdao, Shandong 266033, P.R. China