Correspondence to: Dr. L1 Yunchuan, Department of Otolaryngology Head and Neck Surgery, Beijing Tongren Hospital, Capital Medical University; State Key Laboratory Otolaryngology Head and Neck Surgery of Ministry of Education, Beijing 100730, China (Tel: 86-10- 58269331. Fax: 86-10-58269320. Email: liytmchuan_ent@163.com)