This study comprises the first initial VFSS assessment-based evaluation of clinical predictors of dysphagia in patients with acute and subacute TCSCI in South Korea and provides critical insights into the factors that influence swallowing dysfunction in settings where VFSS may not be readily accessible. Our findings identify tracheostomy as a robust predictor of penetration–aspiration, and highlights its importance in the clinical assessment for dysphagia. However, this association may reflect both the physiological effects of the tracheostomy itself (e.g., mechanical tethering, reduced laryngeal sensation) and the underlying respiratory compromise or neurological severity that necessitated the procedure. Given the retrospective nature of this study, causal inference is limited, and we interpret tracheostomy as a marker of clinical vulnerability rather than a direct cause. Moreover, age ≥ 65 years was recognized as an independent predictor of pharyngeal residue, and emphasizes its relevance in managing older patients who are at risk of swallowing difficulties. These results are valuable for predicting dysphagia in patients with TCSCI undergoing postoperative transitioning to oral intake and for informing individualized clinical decisions for preventing aspiration-related respiratory complications in acute-phase patients receiving enteral nutrition or maintained on nil-by-mouth status.

Tracheostomy significantly affects dysphagia in patients with spinal cord injury, particularly CSCI, and has been consistently identified as a predictor of dysphagia in this population [3, 11, 27]. For instance, one multivariate regression analysis reported an OR of 16.41, which indicated a higher predictive value, as compared to the OR of 8.33 [3] observed in our study. Our findings are in line with the previous results, and confirm that tracheostomy remains a strong and consistent risk factor across different clinical settings and study designs. A VFSS-based study has similarly reported an increased risk of aspiration in the presence of a tracheostomy tube [28]. Proposed mechanisms for tracheostomy-induced dysphagia include reduced laryngeal elevation due to mechanical tethering, pharyngeal compression by the tube cuff, desensitization from prolonged upper airway bypass, and impaired laryngeal coordination [24]. However, previous studies frequently focused on non-traumatic spinal cord injuries or chronic patients and, in some cases, did not utilize VFSS, which is the gold standard for dysphagia evaluation.

This study particularly demonstrated comparable findings, using initial VFSS, in patients with acute and subacute TCSCI. In the acute phase following tracheostomy, patients are typically nasogastric tube-fed or maintained on nil-by-mouth status, which is associated with a risk of occult silent saliva aspiration, which is particularly concerning in tracheostomized patients. Up to 77% of aspiration events occur without overt signs and are only detectable via instrumental assessment [29]. The risk of aspiration in tracheostomized patients remains high, even without oral intake. Moreover, VFSS or FEES may not be feasible in cases that involve facial trauma or other complicating factors. Therefore, recognizing tracheostomy in the acute phase as a significant risk factor for saliva aspiration is critical. Comprehensive management, including meticulous oral hygiene, regular suctioning, monitoring for aspiration pneumonia, and timely antibiotic administration, is essential to prevent complications and improve outcomes in patients with acute TCSCI with tracheostomy. Although speech-language pathologists (SLPs) are not yet systematically integrated into acute dysphagia care in all Korean hospitals, their role in the interdisciplinary management of oropharyngeal dysphagia is increasingly recognized. In our current setting, dysphagia is managed collaboratively by rehabilitation physicians, occupational therapists, and nurses, with shared responsibilities including clinical assessment, positioning, oral hygiene, and dietary modifications. Recent systematic reviews have demonstrated that therapy interventions delivered by SLPs, including compensatory strategies, rehabilitative exercises, and behavioral therapies, can significantly improve swallowing function in patients with oropharyngeal dysphagia [30]. Incorporating trained SLPs into acute care teams could enhance the quality of assessment, individualized treatment planning, and patient education, ultimately improving clinical outcomes. With continued advances in this field, promotion of interdisciplinary collaboration and expansion of access to specialized dysphagia therapy, including the involvement of SLPs, should be prioritized to optimize recovery in patients with TCSCI.

The aging-related changes in swallowing function (presbyphagia [31]) are primarily attributed to alterations in the nervous system, skeletal structure, muscle function, and respiratory capacity [32]. During the pharyngeal phase of swallowing, which involves bolus movement from the pharynx to the upper esophageal sphincter, marked variability exists among older adults. For instance, a study involving 56 healthy older adults revealed that only 16% exhibited a normal pharyngeal phase [33]. Furthermore, aging-related increases in pharyngeal residue have been documented, although this residue does not necessarily result in clinical complications [34, 35].

Conversely, in a population of older patients who underwent VFSS owing to dysphagia, approximately 28% demonstrated pharyngeal residue, wherein larger residue volumes correlated with a heightened risk of aspiration [36]. Another comparative study of VFSS findings among individuals older than 65 years, with and without pneumonia, indicated significantly greater pharyngeal residue in the pneumonia group [37].

In TCSCI, the swallowing function may be impaired owing to associated lower cranial nerve injuries. Postoperative conditions, including edema and medications, can further impair pharyngeal sensation, reducing the clearance of pharyngeal residue [38]. Although our data showed that age ≥ 65 years was independently associated with pharyngeal residue, recent evidence suggests that cervical SCI itself disrupts swallow-breathing coordination and laryngeal control, independently of aging-related changes [39]. Specifically, bilateral diaphragm suppression and altered respiratory phase coordination have been observed, and contribute to dysphagia even in younger patients. These findings suggest that pharyngeal residue in TCSCI arises from a combination of neurogenic and aging-related mechanisms and should be regarded as a critical risk factor for delayed aspiration. The PRSRS used in this study identified significantly increased odds among individuals aged ≥ 65 years. This finding aligns with previous studies on presbyphagia [40, 41], and extends their observations to a population with acute traumatic cervical spinal cord injury. Moreover, the ability to generate an effective cough is compromised frequently following cervical SCI itself [42]. Thus, VFSS or FEES should be performed in older patients with cervical SCI once medically stable, even in the absence of overt signs of dysphagia.

Anatomical changes in the spine or soft tissue edema may reasonably be expected to affect swallowing function; however, evidence remains limited in TCSCI cases. To date, only one recently published study has investigated alterations in the retropharyngeal space associated with dysphagia during the acute phase of TCSCI [43]. That study measured retropharyngeal space width on sagittal CT images and confirmed that the degree of edema influenced dysphagia severity. In healthy adults, position-induced reductions in OD have been identified as contributory factors to dysphagia [18]. Therefore, we measured and analyzed OD using VFSS images in this study. Although intergroup differences in OD were observed at varying aspiration risk levels, these differences did not reach statistical significance. A prospective study that incorporates standardized and feasible methods to quantify edema, such as reproducible measurements from VFSS or adjunctive imaging, may help clarify its clinical relevance in TCSCI.

Cervical alignment, including the dC2–C7 angle, has been implicated in dysphagia. Prior research on cervical alignment has mainly focused on elective cervical surgeries. A previous study demonstrated that changes in the C2–C7 angle from before to after surgery significantly influenced the development of dysphagia. Cervical lordosis > 5° significantly increased the risk of dysphagia in patients without neurological impairment who were undergoing elective cervical surgery. This exaggerated curvature may lead to posterior pharyngeal wall compression, reduced pharyngeal clearance, and impaired laryngeal elevation, all contributing to postoperative dysphagia [19]. However, these findings are not directly applicable to patients with TCSCI owing to the lack of pre-injury alignment data, which limits our ability to assess alignment changes over time. In this study, measurements were performed only once, using postoperative VFSS images. Although cervical lordosis appeared more pronounced in groups with higher penetration-aspiration risks and mild-to-severe pharyngeal residue groups, it did not reach statistical significance as an independent predictor in the multivariate regression analysis. This may be attributable to challenges in standardizing patient positioning in TCSCI, given that factors such as cervical braces, pain, and postural instability can affect imaging consistency.

Similarly, the lack of pre- and post-injury comparisons should be considered when interpreting these results. The O–C2 angle represents upper cervical lordosis; when the angle decreases and leads to kyphosis, it may be associated with oropharyngeal stenosis, which potentially causes dysphagia [44]. However, this study did not find a significant association, which possibly stems from the methodological limitations observed with the C2–7 angle. Although cervical alignment was not identified as a significant predictor of dysphagia in this study, the trends observed in this study suggest the need for further investigation with longitudinal data and standardized protocols to better understand the potential role of cervical alignment in swallowing dysfunction.

The neurological level, degree of paralysis, and anterior surgical approach are well-established predictors of dysphagia in patients with SCI. However, these factors did not reach statistical significance in this study [38]. This result may reflect the complex interplay of variables that affect the swallowing function during the acute phase of TCSCI, and further underscores the need for comprehensive future research.

This study had several limitations. As a single-center, retrospective study with a relatively small sample size, the potential for selection bias cannot be excluded. Moreover, the non-standardization of the timing of VFSS and ISNCSCI assessments may have influenced the results. To address these limitations and validate our findings, future multicenter prospective studies with standardized protocols are recommended.

In conclusion, this study identified tracheostomy and advanced age (≥ 65 years) as significant early predictors of dysphagia in the acute and subacute phases of TCSCI. The potential for aspiration should be carefully evaluated in patients with these risk factors. Early bedside screening, followed by a timely instrumental assessment such as VFSS, is essential to detect dysphagia before oral intake is initiated. Implementing preventive strategies based on these assessments may help reduce the risk of saliva aspiration and its related complications.