Introduction

Infarct pattern referring single or multiple infarction lesions of patients with ischemic stroke is a feasible imaging marker to predict future stroke recurrence [1]. The underlying mechanism of infarct pattern due to large artery atherosclerosis has not been well studied. Taking advantage of the newly developed three dimensional (3D) combined intra- and extra-cranial vessel wall magnetic resonance (MR) imaging technique based on T1 weighted variable-flip-angle turbo spin echo (SPACE) with isotropic 0.55 mm high resolution and improved cerebrospinal fluid suppression [2], it is capable to visualize the arterial vessel wall from common carotid artery to distal segments of intracranial arteries for comprehensive evaluating ischemic stroke etiology and recurrence risk. The aim of this study was to detect large artery atherosclerosis features resulting in single or multiple infarction lesions in patients with non-cardiac acute and sub-acute ischemic stroke using the combined intra- and extra-cranial vessel wall MR imaging method.

Materials and Methods

The study was approved by the local institutional review board and all patients had given the written informed consent before MR imaging. 55 patients with non-cardiac acute and subacute ischemic stroke were retrospectively collected from 2016 to 2017 in one imaging center. Inclusion criteria included ischemic stroke confirmed by diffusion weighted imaging (DWI) within 30 days and caused by larger artery disease. Patients with potential cardiac embolism were excluded. All patients had underwent routine MR Imaging, DWI and 3D high resolution combined intra- and extra-cranial vessel wall MR imaging with (post-contrast) and without contrast agent (Figure 1) on a 3T MR system (MAGNETOM TIM Trio, Siemens, Germany). Stroke etiology was diagnosed according to both imaging findings and clinical evidences by two experienced neurologists in consensus. Based on DWI findings, patients were divided into 2 groups for comparison according to infarct pattern: (1) single infarction lesion in one vascular territory, and (2) multiple infarction lesions in single or multiple vascular territories. For patients with large artery atherosclerosis, the location and number of the plaques identified with focal or diffuse eccentric vessel wall thickening were recorded. In addition, all detected plaques were then categorized based on plaque location (Intracranial or extracranial arterial plaques) and infarct pattern (single-lesion or multiple-lesion pattern). Also the culprit and non-culprit plaques were discriminated by the same two neurologists with consensus according to Qiao et al [3]. For post-contrast vessel wall images, plaque enhancement was assessed as Grade 0 (no enhancement or similar to the enhancement of normal vessel wall), Grade 1 (mild to moderate enhancement less than post-contrast pituitary), and grade 2 (obvious enhancement similar to post-contrast pituitary). Intraplaque hemorrhage was also identified. The clinical demographics of the patients with large artery atherosclerosis and characteristics of the identified culprit plaques were statistically compared between single-lesion and multiple-lesion groups. A comparison for characteristics of all detected plaques between intracranial and extracranial arteries was also performed.

Results

A total of 55 patients (45.53±12.06 years, 46 male) were included in the study. 19 patients showed single-lesion pattern and 36 patients showed multiple-lesion pattern. The stroke etiology was diagnosed as follows: large artery atherosclerosis: 43; artery dissection: 3; Moyamoya disease: 2; vasculitis: 2 and other etiology: 5. There was no significant difference of the stroke etiology between single-lesion group and multiple-lesion group. Among the 43 patients with large artery atherosclerosis, 14 patients showed single-lesion pattern and 29 patients showed multiple-lesion pattern. And 21 and 64 culprit lesions were identified in the two groups, respectively. The clinical demographics of the 43 patients and characteristics of the identified culprit plaques for the two patterns were summarized in Table 1. Plaque enhancement of culprit plaques was significantly more prominent in multiple-lesion pattern group than single-lesion pattern group (p=0.004). A representative single-lesion pattern diagnosed on DWI image and the culprit plaque identified on vessel wall MR images were shown in Figure 2. The comparison of all detected plaques of patients with large artery atherosclerosis between intracranial and extracranial arteries were summarized in Table 2. There was significant difference of prevalence of culprit lesion between intracranial and extracranial arteries (p=0.009).

Discussion and Conclusion

The results of this study indicate that in large artery atherosclerosis, infarct pattern may be associated with the vulnerability of atherosclerotic plaques. And compared with intracranial arterial plaques, extracranial arterial plaques may characterize more vulnerability. And this is still needed to be confirmed in a large-scale patients with arterial atherosclerosis in our near future study. In conclusion, the 3D combined vessel wall imaging is a clinical useful approach and can be used to explore the vascular pathology and predict recurrence of ischemic stroke.

Acknowledgements

This work was supported in part by National Key R&D Program of China (2016YFC0100100) and Key Laboratory for Magnetic Resonance and Multimodality Imaging of Guangdong Province (2014B030301013).

References

1. Wen H et al. Neurology, 2004;63(7): 1317-1319. 2. Zhang L et al. MRI 2017; 44:65-71. 3. Qiao Y et al. Radiology 2014; 271(2): 534-542.