1. Sen-En Rifu Otologic Surgery Center, Miyagi, Japan;
2. Department of Otolaryngology-Head and Neck Surgery, Tohoku University, Graduate School of Medicine, Sendai, Miyagi, Japan;
3. Department of Otolaryngology-Head and Neck Surgery, Kansai Medical University, Hirakata, Osaka, Japan;
4. Department of Diagnostic Radiology, Tohoku University Hospital, Sendai, Miyagi, Japan