Acute myelitis is a neuroinflammatory disease involving the spinal cord, characterized by an acute onset, severe symptoms, and a very poor prognosis, with up to two-thirds of patients experiencing moderate to severe disability (1). Approximately 50% of patients suffer from paraplegia, which predisposes them to pulmonary dysfunction (2). In patients with severe myelitis, the incidence of pulmonary infection is even higher due to the severity of the condition and associated motor dysfunction. Pulmonary infections due to myelopathy have been found to occur in 24.6 to 35.5% (3, 4). Not only do pulmonary infections prolong hospital stays and increase medical costs (5), but they also serve as significant risk factors for mortality (6, 7). The occurrence of pulmonary infection can have an important effect on the prognosis of patients with myelitis. Therefore, early screening of high-risk groups for pulmonary infection, implementation of stratified management and active intervention have important clinical significance for improving patient prognosis and reducing disability.

In patients with acute myelitis, there are differences in the level and extent of spinal cord lesions, with thoracic spinal cord involvement being the most common, followed by cervical and lumbar spinal cords involvement. This difference in spinal cord lesion segments can affect the occurrence and severity of infection to some extent. As a neuroinflammatory disease, inflammation and immunity play an important role in the pathogenesis of acute myelitis. Several studies have found that inflammation and immune status are closely related to infection, disease severity and prognosis (3, 8–10). Decreased nutrition and metabolism tend to affect the body’s immunity, thereby increasing susceptibility to infection (11, 12). These factors may potentially contribute to the development of pulmonary infections in patients with severe myelitis (13, 14).

The aim of this study was to investigate the predictive factors for pulmonary infection in patients with severe myelitis, construct a prediction model by drawing a nomogram, and test the predictive power and clinical applicability of this model, providing a reference and direction for clinicians’ early assessment and proactive intervention.

In this study, we performed the first early prediction of concurrent pulmonary infection in patients with severe myelitis by admission indicators. The results showed that NPAR and high cervical cord lesions were independent risk factors for the development of pulmonary infection in patients with severe myelitis. A nomogram model was constructed based on two variables, NPAR and high cervical spinal cord lesions. C-index, calibration curve, Hosmer-Lemeshow goodness-of-fit test, and decision curve analysis confirmed that the prediction model has good consistency and clinical applicability. Furthermore, the ROC results indicated that the combination of NPAR and high cervical cord lesions had higher accuracy in evaluating the occurrence of pulmonary infections in patients. These findings will guide clinicians in their stratified management and early intervention for similar patients to improve their prognosis.

NPAR is a novel biomarker that has received increasing attention in recent years, which combines neutrophils percentage and albumin to more comprehensively reflect the body’s status in terms of inflammation, immunity, and nutrition. It has been used to assess disease severity, prognosis, and infectious complications in various of diseases (9, 17, 18). In the acute phase of severe myelitis, a large number of inflammatory mediators are released, leading to neutrophil recruitment and activation, further amplifying the inflammatory response. As the most abundant leukocytes in blood, neutrophils are the first line of defense against invading pathogens and play a crucial role in innate immune responses (19). Neutrophils exhibit chemotaxis toward immune cells, phagocytosis of pathogens, and disruption of immune tolerance. They also participate in establishing the inflammatory environment by producing and releasing reactive oxygen species, cytokines, proteases, and other tissue-damaging molecules, while modulating adaptive immunity. When the neutrophil percentage increases, the body inflammation increases and immune imbalance, and susceptibility to infection increases (20).

Accumulated evidence suggests that the presence of an inflammatory response during the acute phase of the disease can significantly impact the nutritional status of the body, leading to hypoproteinemia (21). Albumin is the main protein in human plasma and plays various physiological functions including maintaining osmotic pressure, binding plasma molecules, detoxifying, immune and inflammatory regulation (22, 23). Studies have found that albumin not only inhibits neutrophil migration but also reduces cytokine production, thereby exerting anti-inflammatory effects (24, 25). Given the important role of albumin in reflecting the body’s nutritional status, decreased levels may lead to impaired immune function and increase the risk of infection (26). Additionally, a retrospective study has also demonstrated that low albumin levels increase the risk of central nervous system infections and mortality (27).

The pulmonary infection in patients with severe cervical spinal cord lesions may be related to the following reasons. Firstly, the phrenic nerve is composed of the anterior branches of the third, fourth, and fifth pairs of cervical nerves. When the C3-C5 spinal cord is injured, the diaphragm muscle innervated by the phrenic nerve becomes paralyzed. As the major inspiratory muscle, its impairment can partially or completely restrict the inspiratory function, leading to ventilation disorders and, in severe cases, even suffocation. Secondly, in high cervical spinal cord injury, the sympathetic innervation to the lungs is weakened while the activity of the vagus nerve is enhanced, resulting in decreased levels of circulating adrenaline and increased airway resistance, leading to airway narrowing (28). Thirdly, with high cervical cord lesions, the pathway from the brainstem respiratory center to the respiratory motor neurons in the cervical and thoracic regions of the spinal cord is blocked, causing respiratory muscle paralysis. This leads to a decrease in respiratory capacity and clearance ability of the airways, increasing the risk of ineffective coughing, mucus retention, and atelectasis (29). Finally, high cervical cord injury causes limb paralysis, reduces chest wall compliance, increases abdominal wall compliance, and results in increased chest stiffness and respiratory effort. Therefore, high cervical cord lesions are closely associated with the occurrence of pulmonary infection. In clinical practice, for patients with high cervical cord disease, attention should be paid to respiratory management to reduce the risk of pulmonary infection and thus improve the prognosis of patients.

Due to the severity of their condition and long-term bed rest, patients with severe myelitis are extremely susceptible to pulmonary infections. The occurrence of pulmonary infections will aggravate the patient’s condition, increase the difficulty of treatment, prolong hospitalization time, and seriously affect the patient’s prognosis and mortality (30, 31). Therefore, early screening of possible populations with pulmonary infections is crucial for improving the prognosis of myelitis and reducing mortality. A nomogram model based on the combination of NPAR and high cervical myelopathy exhibits favorable predictive performance and clinical applicability, which can not only help clinicians to early predict the occurrence of pulmonary infection in patients and perform stratified management, but also guide clinicians to determine the focus and direction of intervention to reduce the risk of pulmonary infection in patients.

This study has certain limitations. Firstly, it is a single-center, retrospective study, which may introduce selection bias. Additionally, due to limited data availability, external validation was not conducted. Furthermore, there are some shortcomings in the model, which may be related to some influencing factors are not included and require further study.

In conclusion, we found that NPAR and high cervical cord lesions are closely associated with the occurrence of pulmonary infections in patients with severe myelitis. The nomogram model combining the two can efficiently and reliably predict the occurrence of pulmonary infection in patients with severe myelitis, which may provide reference and inspiration for further studies.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving humans were approved by the Ethics Committee of the First Affiliated Hospital of Zhengzhou University. The studies were conducted in accordance with the local legislation and institutional requirements. The ethics committee/institutional review board waived the requirement of written informed consent for participation from the participants or the participants’ legal guardians/next of kin because written informed consent from the participants’ legal guardian/next of kin was not required to participate in this study in accordance with the national legislation and the institutional requirements.

FY: Formal analysis, Methodology, Software, Writing – original draft, Writing – review & editing. RD: Data curation, Writing – review & editing. YW: Data curation, Writing – review & editing. JG: Data curation, Writing – review & editing. QZ: Data curation, Writing – review & editing. LW: Data curation, Writing – review & editing. PH: Writing – review & editing. JQ: Writing – review & editing. DS: Data curation, Writing – review & editing. ZR: Data curation, Writing – review & editing. JT: Project administration, Writing – review & editing. WM: Funding acquisition, Project administration, Supervision, Writing – review & editing.