Perforator artery disease (PAD), which accounts for approximately one-quarter of all ischemic strokes, was defined as an acute isolated infarct in the clinically relevant territory of perforator arteries such as the basal ganglia region and brainstem (1). According to the CISS typology, the probable pathogenesis of PAD includes atherosclerosis at the proximal segment of the penetrating arteries and lipohyalinotic degeneration of arterioles (2, 3). The diagnostic criteria include the following: (1) acute isolated infarct in the clinically relevant territory of one penetrating artery, regardless of the size of the infarct; (2) no evidence of atherosclerotic plaque (detected by HR-MRI) or any degree of stenosis in the parent artery (detected by TCD, MRA, CTA, or DSA); (3) with evidence of vulnerable plaques or stenosis ≥50% in ipsilateral proximal intracranial or extracranial large arteries, or cardiac disease that has a potential for embolism is classified in UE (multiple etiology); (4) other possible causes have been excluded. Due to different anatomical structures, patients with PAD also differ from those with large artery atherosclerosis in terms of pathogenesis, clinical features, and prognosis (4). Previous studies have shown that patients with PAD are prone to early neurological deterioration (END) and progressive movement disorders (PMD) (5, 6), but the risk factors affecting the prognosis of patients with PAD are unclear. Studies have suggested that neutrophil-to-lymphocyte ratio (NLR) affects post-thrombolysis early neurological outcomes in patients with large-vessel occlusive stroke (7, 8), but the effect on patients with PAD is rarely reported. Using the data from Dushu Lake Hospital affiliated to Soochow University, we analyzed the potential predictors for unfavorable outcomes in patients with PAD, as well as the correlation between NLR, an indicator of inflammation, and the prognosis of PAD and its clinical application value.

A total of 181 patients with PAD were chosen according to the inclusion and exclusion criteria, comprising 112 male patients and 69 female patients, of which 133 patients were in the favorable prognosis group and 48 patients were in the unfavorable prognosis group. The demographics and clinical characteristics of the two groups are shown in Table 1. Univariate logistic analysis showed that patients in the unfavorable prognosis group were older (median 66 versus 63, p = 0.019) and NIHSS scores at admission (median 5 versus 2, p < 0.001), baseline NE (median 4.93 versus 3.94, p = 0.003), and NLR were higher (median 3.53 versus 2.25, p < 0.001) than those in the favorable prognosis group, whereas the baseline LYM was lower (mean 1.35 versus 1.92, p < 0.001) in the unfavorable prognosis group. There were no statistical differences between the two groups in terms of other demographic characteristics, vascular risk factors, clinical assessment, lesion location, and laboratory data (p > 0.050). Figure 2 shows the boxplots of inflammatory indices between the two groups.

Table 2 displays the results of the multiple logistic regression models for subgroups according to prognosis. Due to the correlation between NE, LYM, and NLR, we divided into two models for analysis. Furthermore, we incorporated potential risk factors of BMI, diabetes mellitus, HDL, SBP, and WBC (p < 0.1). In addition, due to the correlation between WBC NE and LYM, in Model 1, we removed the confounder WBC. After adjustment for all potential confounders, Model 1 showed that age (odds ratio [OR], 1.092; 95% confidence interval [CI] 1.019 ~ 1.171, p = 0.013), NIHSS (OR, 3.123; 95% CI 1.975 ~ 4.938, p < 0.001), NE (OR, 1.889; 95% CI 1.200 ~ 2.975, p = 0.006), and LYM (OR, 0.054; 95% CI 0.011 ~ 0.257, p < 0.001) were identified as independent factors for unfavorable prognosis for patients with PAD, while Model 2 also showed that age (OR, 1.076; 95% CI 1.012 ~ 1.144, p = 0.019), NIHSS (OR, 2.930; 95% CI 1.905 ~ 4.508, p < 0.001), and NLR (OR, 3.028; 95% CI 1.6154 ~ 5.675, p = 0.001) were identified as independent factors for unfavorable prognosis for patients with PAD.

The ROC curves, which were depicted in Figure 3, were used to test the overall discriminative ability of risk factors for unfavorable prognosis for patients with PAD. We observed in Model 1 that the areas under the curve (AUC) of NE and LYM were 0.636 (95% CI, 0.538–0.734) and 0.768 (95% CI, 0.693–0.843) and the composite diagnostic model was 0.960 (95% CI, 0.935–0.984), and in Model 2, the area under the curve (AUC) of NLR was 0.798 (95% CI, 0.727–0.869) and the composite diagnostic model was 0.956 (95% CI, 0.930–0.982). In the performance of predicting prognosis of PAD, the AUC of NLR was superior to NE (0.798 versus 0.636, p < 0.001) and LYM (0.798 versus 0.768, p < 0.001), which means that NLR may be a better biological indicator to predict the prognosis of stroke with PAD. We also established optimal cutoff values at which the Youden Index was highest. The details are described in Supplementary Table S1.

Furthermore, patients with PAD were divided into the anterior circulation group (n = 104) and posterior circulation group (n = 77) according to the lesion site shown on the images, and the changes of inflammatory indices NE, LYM, and NLR were analyzed to see whether there was any difference between the two groups. The results shown in Table 3 suggested that the decrease in LYM and the increase in NLR in the anterior circulation group were significantly correlated with an unfavorable prognosis and that the increase in NE and NLR as well as the decrease in LYM in the posterior circulation group were all significantly correlated with an unfavorable prognosis (p > 0 05).

Our study showed that increasing age, higher NIHSS score at admission, decreased LYM, and elevated NE and NLR were significantly associated with unfavorable prognosis in patients with PAD. Further multifactorial analysis showed that elevated NLR was independently associated with an unfavorable prognosis. Further subgroup analysis showed that NLR correlated with unfavorable prognosis in both anterior and posterior groups, which suggests that inflammation and immune factors may play an essential role in the clinical regression process of PAD and the use of NLR to predict prognosis in PAD deserves further investigation.

Aging exacerbates the damage and dysfunction of different components of the non-injurious brain unit, affecting the integrity of the neurovascular unit and the vulnerability to neurodegeneration, thus accelerating the progression and deterioration of brain injury (12). The National Institute of Health Stroke Scale (NIHSS) is currently the most used clinical scale for assessing neurologic deficits. Studies have demonstrated that the more severe a patient’s neurological deficit, the higher the risk of poor prognosis (13). This study further confirms that aging and elevated baseline NIHSS are risk factors for unfavorable prognosis of PAD.

Acute ischemic stroke triggers an inflammatory response at an early stage, leading to the disruption of the blood–brain barrier and the deterioration of neurological function (14, 15). Studies have shown that neutrophils promote atherogenesis and the progression of atherosclerosis by mediating a non-specific inflammatory response (16, 17), and the infiltration of neutrophils can cause an increase in cerebral infarct volume and worsening of ischemic brain damage (18). Whereas lymphocytes have a role in maintaining immune homeostasis and immune tolerance, they can repair damage through inflammatory responses (19, 20). Tregs in lymphocytes are key cerebroprotective immunomodulators in acute stroke (21), which act as endogenous neuroprotective modulators in maintaining blood–brain barrier permeability, delaying leukocyte infiltration, reducing tissue edema, decreasing brain damage, and playing a protective role in improving prognostic recovery (22–24). Lack of lymphocytes can accelerate the process of atherosclerosis progression (25, 26). Previous studies have found that there is a significant tendency for lymphocytes to decrease at the onset of cerebral infarction (27, 28), and although immunosuppression may reduce brain damage, it may impede neuronal cell repair and increase the risk of systemic bacterial infections during the acute phase of the disease (29, 30). Elevated levels of NLR have been observed in diabetic patients who develop renal arterial vitreous degeneration (31, 32), while lipohyalinotic degeneration is the main pathogenesis of PAD, so we hypothesized that elevated NLR plays a role in the development of PAD and may be involved in the progression of penetrating arterial lesions. In the present study, we observed that elevated NLR was independently associated with unfavorable functional outcomes in PAD, suggesting that mediating the inflammatory response could be a new target for the prevention and treatment of PAD.

As a retrospective study, our study has some limitations. First, this study only collected data on baseline inflammatory markers after emergency or admission and did not assess the dynamic changes in NLR during hospitalization, which may provide information for discovering the pathophysiological mechanisms of the inflammatory response after the onset of PAD (33). Second, the single-center study was not fully representative of the total patients with PAD. Moreover, the sample size is small, and there is a possibility of bias in some clinical characteristics. Therefore, more prospective, large-sample, multicenter studies are needed for further validation. Despite these limitations mentioned above, it is the first time the relationship between inflammatory indices and neurological outcomes of PAD was explored, and this can be validated in the future research.

In summary, our study showed that elevated baseline NLR and NIHSS scores and aging may be independent risk factors for unfavorable prognosis in patients with PAD. NLR can be used as a potential biological indicator for predicting the prognosis of PAD, suggesting that intervening in the inflammatory response is expected to be a new target for preventing and treating stroke.

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 Suzhou Dushu Lake Hospital. The studies were conducted in accordance with the local legislation and institutional requirements. The participants provided their written informed consent to participate in this study.

LS: Writing – original draft, Data curation, Formal analysis, Methodology, Software. XL: Data curation, Software, Writing – original draft. WH: Formal analysis, Software, Writing – original draft. LY: Data curation, Software, Writing – review & editing. SG: Data curation, Methodology, Writing – review & editing. YJ: Supervision, Visualization, Writing – review & editing. HP: Conceptualization, Supervision, Writing – review & editing. YH: Conceptualization, Visualization, Writing – review & editing.