Introduction

Intracranial atherosclerotic stenosis (ICAS), especially the middle cerebral artery (MCA) involvement, is the main cause of acute ischemic stroke (AIS) or transient ischemic attack (TIA)[1-2]. However, TIA patients have a higher chance of subsequent ischemic stroke, which seriously affects the survival status of TIA patients [3-4]. The occurrence of stroke is related to the vascular lumen characteristics, plaque characteristics and cerebral blood flow defects of ICAS[5]. Previous studies used high-resolution magnetic resonance imaging (HRMRI) to characterize plaque features and dynamic sensitivity contrast-enhanced (DSC) perfusion-weighted imaging (PWI) to reflect hemodynamic injury[6]. However, there are no studies on the difference in DSC and ASL perfusion to characterize the hemodynamic changes in patients with intracranial artery stenosis. Therefore, DSC and ASL were used to investigate the differential hemodynamics of MCA in patients with ischemic stroke and TIA, and tried to establish a predictive model of ischemic stroke together with clinical risk factors in this study.

Materials and Methods

Consecutive patients with sICAS were retrospectively collected from October 2020 to December 2021. All patients underwent MR imaging using a 3.0 T MR scanner (Ingenia CX, Philips Healthcare,) with a 32-channel head coil. A total of 32 participants were finally evaluated, and 12/20 were assigned to TIA/stroke group (table 1). Two experienced neuroradiologists were blinded to any clinical information, evaluated blood perfusion information in the MCA area on the DSC images and ASL (2-PLD: 1500 ms, 2500 ms) images, mirror measured CBF on the affected and unaffected side. And to define the perfusion reduction as: DSC-Hypoperfusion: (DSC-rCBFa - DSC-rCBFu)/DSC-rCBFa≥10%；1500msASL-Hypoperfusion：(1500msASL-CBFa - 1500msASL-CBFu)/1500msASL-CBFa≥10%；2500msASL-Hypoperfusion：(2500msASL-CBFa - 2500msASL-CBFu)/2500ASL-CBFa≥10%. If the CBF perfusion reduction of the above sequence is inconsistent, it is defined as a perfusion mismatch. Logistic regression (binary variables) analyses were performed to assess the different features between TIA and stroke group. Variables with P values <0.05 were entered into the multivariate logistic analysis. Receiver operating characteristic (ROC) curves were used to evaluate the diagnostic performance of the different models. All tests were twosided and performed by using SPSS (version 26, IBM) where appropriate. A significant difference was assumed if p < 0.05.

Results

Figure 1 shown two typical examples of images and measurements. Compared with the TIA group, the stroke group had significantly more patients with hyperhomocysteinemia (Table 1). 2500msASL-Hypoperfusion, DSC-2500msASL mismatch were significantly higher in stroke than those in the TIA group (Table 2). Multivariable regression analysis revealed that hyperhomocysteinemia and DSC-2500msASL mismatch were risk factors for patients with ischemic strokeafter adjusting for clinical confounding factors ( P = 0.036, 0.043). All other indices shown no significant difference between two groups. In distinguishing between patients with ischemic stroke and TIA, the diagnostic accuracy of the combination of hyperhomocysteinemia and DSC-2500msASL mismatch was higher than that of the above single features (Figure 2). The combination had a significantly higher AUC(95%CI 0.655–0.978, AUC=0.817) than hyperhomocysteinemia (95%CI 0.539–0.911, AUC=0.725) and DSC-2500msASL mismatch (95%CI 0.533–0.900, AUC=0.717), respectively.

Discussion

This study found a difference between the ASL and DSC methods in showing cerebral perfusion abnormalities in patients with ischemic stroke and TIA. Although perfusion showed little difference between the two groups when PLD was 1500ms, ASL and DSC perfusion mismatch was significantly different between stroke and TIA patients when PLD was delayed by 2500ms. This indicates the importance of two PLD to distinguish stroke from that of TIA patients, which side reflects the difference between the perfusion process and the outcome of patients with stroke and TIA. ASL at a PLD of 2500ms in this study showed more stroke patients with hypoperfusion than those demonstrated with DSC. The reason may be the occurrence of post-infarction reperfusion or open collateral circulation in these stroke patients, and the hyperperfusion (magnetized-labeled endogenous water quality is sensitive to BBB damage) is generally poor, so such unmatched patients should pay additional clinical attention[7]. However, in TIA patients, there are fewer mismatched patients and comparable perfusion abnormalities, which may indicate that TIA patients may not break the blood-brain barrier, and additional attention should be paid to TIA patients with mismatched perfusion. Therefore, the prolongation of PLD increases the difference of blood flow abnormalities between TIA patients and stroke patients. ASL with multi-PLD has more clinical value than the ASL with single PLD in intracranial stenosis evaluation.

Conclusion

DSC-2500msASL mismatch may be a biological marker for screening high-risk TIA patients, and we should pay additional attention to this population for more aggressive secondary stroke measures.

Acknowledgements

No acknowledgement found

References

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