INTRODUCTION

Intracranial atherosclerotic disease (ICAD) represents the most common cause of ischemic stroke across the world¹. ICAD has a higher tendency to occur in the middle cerebral artery especially in Asians². Patients with ICAD have increased risk of recurrent stroke³.With the development of high-resolution vessel wall imaging (HR-VWI), more and more attention has been paid to not only the degree of vessel stenosis but also plaque characteristics of ICAD. However, previous studies mostly focused on the plaque features in ischemic stroke. There were few studies in which the analysis of plaque feature, perfusion and pial collaterals (PCs) were all presented⁴. In this study, we aim to investigate plaque characteristics, perfusion and PCs in recurrent ischemic stroke and demonstrate the value of these factors in the identification of the recurrence of ischemic stroke.

METHODS

From February 2018 to July 2021, patients presenting with a transient ischemic attack (TIA) or acute ischemic stroke(AIS) caused by unilateral atherosclerotic middle cerebral artery (MCA) stenosis(>50%) who underwent the routine head MRI/MRA scan，HR-VWI and dynamic susceptibility contrast-enhanced perfusion weighted imaging on an 3.0T MRI scanner(Ingenia 3.0T, Philips Healthcare, Best, the Netherlands) at Zhongda Hospital affiliated Southeast University were recruited. Based on the results of a twelve-month telephone follow-up, 62 patients were divided into group with recurrence (n=12) and group without recurrence (n=50). For all patients, the evaluation of characteristics of culprit plaques (defined as the only lesion or the most stenotic lesion when multiple plaques were present within the same vascular territory of the stroke), PCs and brain perfusion were performed. Plaque characteristics include stenosis grade, lumen area of stenotic lesion (LA_lesion), plaque area, plaque length, standardized wall index (NWI), eccentricity index, remodeling index, and plaque enhancement grade. PCs within the territory of stenotic MCA was evaluated on axial time-of-flight magnetic resonance angiography (TOF-MRA) source images on the level of lateral ventricle body according to a grading system: grade 0, absent vascular signal; grade 1,collaterals<50% compared to the reference side; grade 2,collaterals ≥50% compared to the reference side; grade 3, collaterals equal to or more than the reference side. Brain perfusion within the territory of MCA was visually assessed on a 10-point cerebral blood flow map based on the Alberta Stroke Program Early CT score (CBF-ASPECTS). Each ASPECTS region was scored 0 if abnormal and 1 if normal. Final CBF-ASPECTS for each patient were summed in ten subscores. Plaque features, demographic and clinical characteristics were compared between two groups. Multivariate logistic regression and receiver operating characteristic (ROC) curves were constructed to assess the effect of significant variables alone and their combination on identifying recurrence of ischemic stroke.

RESULTS

Table 1 summarized the demographics and plaque characteristics of group with and without recurrence. The CBF-ASPECTS in group with recurrence was 3.33±2.50, which was significantly lower than that in group without recurrence (7.96±1.31, P<0.01). In addition, PCs was significantly different between the two groups (P<0.01). Longer plaque length was seen in the group with recurrence (P＜0.01, Table 1, Figure 1-2). The three variables were input for the univariate logistic analysis. Multivariate regression was conducted for the variables with p < 0.05 in the univariate logistic analysis. In addition to plaque length (P=0.06), PCs (P<0.01) and CFB-ASPECTS (P<0.01) were associated with recurrence of ischemic stroke in the univariate logistic analysis. After the adjustment of clinical demographic factors, PCs(P=0.04,OR 0.17,95% 0.03-0.95)and CBF-ASPECTS(P<0.01,OR 0.31,95% 0.14-0.71) remained as significant factors in the multivariate logistic analysis (Table 2). Multivariate logistic analysis revealed that high CBF-ASPECTS and PCs were protective factors for recurrence of ischemic stroke. For the differentiation between group with and without recurrence, the diagnostic accuracy of the combination of CBF-ASPECTS and PCs (95%CI 0.93-1.00, AUC =0.97) was higher than that of CBF-ASPECTS (95%CI 0.82-1.00, AUC =0.92) or PCs (95%CI 0.72-0.94, AUC = 0.83) individually (Figure 3).

DISCUSSION

The relationship between plaque length, CBF-ASPECTS, PCs and recurrence of ischemic stroke was observed in our study. A recent study demonstrated that downstream perfusion was valuable in predicting clinical outcomes in ischemic stroke. The mechanism is possibly that hypoperfusion restrict the blood flow's ability to clean emboli and microemboli in distal arteries⁵. PCs provides alternative blood flow to protect cerebral tissue that is in a hypoperfused state. PCs is relevant to the outcome in acute ischemic stroke patients⁶. Our finding was similar to the observation from previous studies. Plaque length was significantly different between two groups but failed to remain significant in the multivariate logistic analysis. We speculate that plaque length may play a weaker role than the other factors in identifying recurrent ischemic stroke. Our findings support that a combined assessment of perfusion and collateral circulation may be useful in identifying the recurrence of patients with ischemic stroke.

CONCLUSION

Hypoperfusion and poor collateral state independently associated with recurrence of ischemic stroke in patients with atherosclerotic MCA stenosis. The combination of brain perfusion and collateral circulation may play a pivotal role in the identification of recurrent ischemic stroke caused by unilateral atherosclerotic MCA stenosis (>50%).

Acknowledgements

No acknowledgement found.

References

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