1. Department of Communication Disorders of Rehabilitation Science, Health Sciences University of Hokkaido, Sapporo, Japan
2. Department of Rehabilitation, Tokachi Rehabilitation Center, Obihiro, Japan
3. Department of Rehabilitation, Nishimaruyama Hospital, Sapporo, Japan
4. Department of Oto-Rhino Laryngology, Head and Neck Surgery, Hokkaido University Hospital, Sapporo, Japan