1. Department of Otolaryngology, Ohtawara Red Cross Hospital, 2-7-3 Sumiyoshi-cho, Ohtawara City, Tochigi 324-8686, Japan
2. Department of Oral Function and Molecular Biology, Ohu University, 31-1 Misumido, Tomita-machi, Koriyama City, Fukushima 963-8611, Japan
3. Department of Otolaryngology, Keio University, 35 Shinano-machi, Shinjuku, Tokyo 160-8582, Japan