4. Discussion
dysphagia, muscle mass, muscle weakness, nausea, fatigue, stomatitis, sarcopenia, vomiting, pain, head and neck cancer, mucositis, muscle contractions, dermatitis
DYSPHAGIA, MUSCLE WEAKNESS, MUSCLE ATROPHY, STOMATITIS, ADVERSE EVENTS, RECRUITMENT, SARCOPENIA, HEAD AND NECK CANCER, MUCOSITIS, SCARRING, DERMATITIS
Although CRT for head and neck cancer has been reported to cause tissue scarring, muscle atrophy, and muscle weakness [Muscle strength is regulated by the muscle fibers and the nerve factors that activate them. Nerve factors control the recruitment and discharge rate of the MU during muscle contractions; the higher the number of MUs and discharge rate, the higher the muscle strength [In the present study, patients underwent eight weeks of muscle-strengthening exercises for the SHMG with TESS. Therefore, it was assumed that muscle exercises would increase the RMS and CoV before and after treatment; however, no such increase was observed. This may be because patients could not perform sufficient strength training due to the pain, fatigue, and nausea caused by mucositis, dermatitis, and stomatitis during CRT. Most of the training performed in this study involved weight-bearing and required physical exertion. Therefore, it seems likely that the patients undergoing CRT could not perform aggressive high-intensity exercises. The second factor is a decline in nutritional status. A high correlation was found between body weight or SMI change rate, an indicator of nutritional status, and RMS or CoV change rate. Patients with decreased body weight and SMI had a decreased discharge rate and distribution of MUs, that is, decreased swallowing muscle strength. Recently, the concept of sarcopenia has been proposed, with many reports that low nutrition causes dysphagia [Although it has been hypothesized that tongue-raising movements correlate with electromyograms of the SHMG [This study had some limitations. First, the sample size was not enough to reach a definitive conclusion and this study was only a pre- and post-treatment comparison, and it is not clear at what stage during treatment each of the parameters changed. Therefore, whether the effects of muscle-strengthening exercises were limited to the first few weeks of treatment was not adequately measured. We realize the need to investigate the changes over time from a prophylactic perspective to reduce adverse events. As most head and neck cancer patients are male in general, all patients were male in this study. It should be mentioned that the gender difference in muscle mass could be relevant to HD-sEMG, muscle strength, and tongue pressure. Although we focused on the body weight, SMI, and MU of the SHMG, there were many acute adverse events during CRT, including mucositis, dermatitis, and vomiting. It was not clear which of these adverse events strongly influenced the treatment completion rate, oral intake maintenance rate, or length of hospital stay; therefore, continued data collection is needed.