1. Department of Otolaryngology and Stomatology, Shouguang People's Hospital, Shouguang, Shandong 262700, P.R. China
2. Department of Otolaryngology and Maxillofacial Surgery, Wuwei People's Hospital, Wuwei, Gansu 733000, P.R. China
3. Department of Otolaryngology, Head and Neck Surgery, The Second Affiliated Hospital of Kunming Medical University, Kunming, Yunnan 650101, P.R. China