1. Department of Otolaryngology, Sapporo Medical University School of Medicine, Hokkaido, Japan
2. Department of Otolaryngology, Obihiro Kyokai Hospital, Hokkaido, Japan
3. Department of Otolaryngology, Hakodate Goryoukaku Hospital, Hokkaido, Japan
4. Tomo ENT clinic, Sapporo, Hokkaido, Japan
5. Sapporo Medical University, Hokkaido, Japan