Objective: To investigate the factors affecting the postoperative swallowing dysfunction in patients who underwent oral cancer surgery. Methods: Retrospective review of clinical records of 70 patients (50 males and 20 females) who underwent oral cancer surgeries from July 2007 to April 2015 were enrolled. Multiple regression analysis was performed using the Food Intake LEVEL Scale (FILS) at discharge as the objective variable and age, tumor size, resection of the tongue base, suprahyoid muscle resection, segmental mandibulectomy, neck dissection and radiation therapy as the explanatory variables in 70 patients. In addition, multiple regression analysis was performed between objective variables, which include maximum hyoid bone movement, laryngeal elevation delay time, pharyngeal constriction ratio (PCR), residue in the vallecular and pear-shaped depression (pyriform sinuses), and Penetration-Aspiration Scale score and one of the main factors representing the characteristics of each case as the explanatory variables, and age was treated as an adjustment factor in 23 patients. Results: The FILS shows significant negative correlation by age and resection of the tongue base. In videofluoroscopic swallowing study, the maximum movement, PCR and residue in the vallecular are significantly correlated with factors demonstrating the characteristic for each case. Conclusion It was suggested that in elderly patients, the presence of more than half of the tongue base resection, suprahyoid muscle resection and neck dissection cause severe dysphagia after surgery.

Background: Although radiotherapy is commonly used to treat head and neck cancer, it may lead to radiation-asso‑ ciated dysphagia (RAD). There are various causes of RAD, however, the mechanism has not yet been fully identified.Currently, the only effective treatment for RAD is rehabilitation. Additionally, there are few available animal models of RAD, necessitating the development of new models to establish and evaluate RAD treatments. We hypothesize that radiation-induced neck muscle fibrosis could be one of the causes of RAD due to impairment of laryngeal eleva‑ tion. Therefore, in this study, we focused on the changes in inflammation and fibrosis of the strap muscles (Sternohy‑ oid, Sternothyroid, and Thyrohyoid muscles) after a single-dose irradiation. This research aims to provide a reference animal model for future studies on RAD. Results: Compared to control mice, those treated with 72-Gy, but not 24-Gy, irradiation had significantly increased tumor necrosis factor-α (TNF-α) (p < 0.01) and α-smooth muscle actin (αSMA) (p < 0.05) expression at 10 days and sig‑ nificantly increased expression levels of motif chemokine ligand-2 (CCL2), α-SMA, tumor growth factor-β1 (TGF-β1), type1 collagen, and interleukin-1β (IL-1β) (p < 0.05) in the muscles at 1 month by real-time PCR analysis. The results of immunohistochemistry showed that the deposition of type 1 collagen gradually increased in extracellular space after radiation exposure, and the positive area was significantly increased at 3 months compared to non-irradiated control. Conclusions A single dose of 72-Gy irradiation induced significant inflammation and fibrosis in the strap muscles of mice at 1 month, with immunohistochemical changes becoming evident at 3 months. This cervical irradiationinduced fibrosis model holds potential for establishing an animal model for RAD in future studies.