Discussion
dysphagia, DSS
DYSPHAGIA, DISEASE, NEUROMUSCULAR DISEASES, DISEASES, CEREBRAL INFARCTION
The TRP was employed for patients with dysphagia for the first time, showing that TP increased after 2-month use. Interestingly, although three participants had progressive disease, TP increased. Therefore, the device can serve as a valuable tool for functional rehabilitation of the tongue in patients with such diseases.A decrease in TP was observed in only one of the eight participants. However, the TP of this participant at baseline was 40.8 kPa, which was not significantly low despite the presence of dysphagia, with a decrease of only 0.8 kPa. Therefore, TRP may not have been very useful in this case. However, TRP could be suitable for dysphagia caused by low TP.Although a few mechanisms associated with TRP and improvement in TP have been reported, a possible explanation might be the lingual–hypoglossal reflex. When filiform papillae on the tongue are mechanically stimulated, the tongue’s tip curves upward, the tongue hollows from side to side with the upward curvature of the lateral edges, and the posterior part is depressedThe ultrasonographic evaluation revealed that the CSA of the GH did not improve in this study (The ODK and PNIF were also measured. The ‘Pa’ of ODK (r = 0.45) and PNIF (r = 0.48) during the follow-up visit tended to increase, but when compared with that of baseline, no significant differences were found. There may be a significant difference between baseline and follow-up values in future studies with a larger sample size. In this study, cases of some patients with progressive disease should have been adjusted or homogenized. Although the improvement was not significant, the PNIF scores increased. This finding is consistent with a previous studyIn contrast, the ‘ta’ and ‘ka’ of ODK decreased slightly. In the ‘ta’ of the ODK, the score of four participants, including the three participants with progressive neuromuscular diseases, increased whereas that of the other two decreased. The ‘ka’ scores of the two participants decreased, while no change was observed in that of the remaining participants. The improvement in the ‘ta’ could be explained by enhanced genioglossal muscle strength, similar to the improvement in TP. However, the ‘ka’ did not change or decrease. Of the two participants whose ‘ka’ decreased, one had progressive disease, and the other had a history of cerebral infarction. The ‘ta’ and ‘ka’ of ODK reflect the anterior and posterior movements of the tongue, respectively. TRP could maintain the movement of the anterior tongue despite the presence of progressive diseases.This study had some limitations. First, only eight participants were included. Further, as we conducted this pilot study before conducting a randomized controlled trial with both TRP and placebo groups, we did not include a control group. Furthermore, confounding factors were not considered in this study. In the subsequent randomized controlled trial, the sample size will be set using the effect size calculated from the result of this study. Additionally, the participants were heterogeneous: the BIs, the FOIS scores, and the DSS ranged from 25 to 100, 2 to 7, and 2 to 4, respectively. Therefore, more studies are required with a larger number of male and female participants to clarify the effectiveness of TRP use in improving oral function. Second, although TP increased, the ultrasound assessment showed no improvement, suggesting that the muscle characteristics did not change after wearing TRP. Third, the increase in TP may be due to the lingual–hypoglossal reflex. However, it was difficult to prove that the reflex had actually occurred. Fourth, we only verbally confirmed the participants’ usage of TRP at 1- and 2-month follow-up visits. Although the compliance of the participants in this study was adequate that all of them wore TRP every night for the 2-month period, a checklist should be distributed to confirm the achievement rate in a future study. Fifth, we did not find any changes in DSS scores, evaluated by videoendoscope, between the initial and 2-month follow-up visits. The range of each DSS score is wide, and the DSS score does not reflect the movement of swallowing-related organs. Moreover, we could not evaluate the tongue’s position. Since the previous study indicated that TRP could improve the tongue’s position, leading to the increase of PNIF, we should have evaluated its position using videofluorography. Lastly, since the period of TRP usage was 2 months, TP possibly decreases after patients stop TRP usage. However, it remains unclear whether the effect of TRP continues even after the interventional period. Therefore, the long-term effect of TRP usage should also be evaluated in the future.This is the first study to consider the oral or swallowing function of TRP users. Therefore, a randomized controlled trial should be conducted in future studies to emphasize the effectiveness of TRP in oral function. Considering that the ES of TP is 0.84 in this study, 48 participants, including 24 with TRP and placebo oral device (α = 0.05, power = 0.8), are required. Furthermore, since we did not observe any changes via the videoendoscope, swallowing evaluations with videofluorography should be conducted to observe the changes in swallowing kinematics and anatomical characteristics in future studies.Numerous exercises have been suggested to improve TP