Introduction

Deep medullary veins (DMVs) and asymmetrically prominent cortical veins (APCVs) have been observed in ischemic stroke^{1, 2}. Although the relationship between DMVs/APCVs and stroke prognosis have been explored in previous studies, controversy persists about the impact of DMVs and APCVs on prognosis. In this study, we explored the relationship between DMVs, APCVs, middle cerebral artery (MCA) thrombosis, the size of cerebral infarction, and Admission and Discharge National Institute of Health Stroke Scale (NIHSS) scores in patients with MCA occlusion using the susceptibility-weighted imaging and mapping technique (SWIM).

Methods

A total of 73 patients were retrospectively included in our study. The inclusion criteria were: 1) the middle cerebral artery territory showed hyperintensity on diffusion-weighted imaging (DWI) and hypointensity on apparent diffusion coefficient (ADC) images; 2) the patient had a unilateral MCA occlusion confirmed by Time-of-Flight MR Angiography (TOF-MRA) and corresponding thrombosis confirmed by susceptibility-weighted imaging (SWI); 3) the clinical information and imaging information were complete. The exclusion criteria were: 1) the patient had MR contraindications; 2) the patient had bilateral MCA occlusion; 3) the patient had other diseases, including cerebrovascular malformations, tumor, brain trauma, neuropsychiatric disorder, hemorrhage, or previously undergone neurosurgery. The patients were divided into a DMVs group (16 patients), a non-DMVs group (57 patients), an APCVs group (41 patients), and a non-APCVs group (32 patients) based on the imaging evidence of DMVs/APCVs (Fig. 1). MRI data were collected on a MAGNETOM Trio Tim 3T MR scanner (Siemens, Erlangen, Germany), including a routine head scan plus a SWI scan. The parameters of SWI were: TR/TE=27/20ms; field of view=230×200mm²; receiver bandwidth=120 Hz/pixel; flip angle=15°; number of slices=56; acquisition time=179 sec; voxel size=0.5×0.5×2.0mm³. SWIM was reconstructed using both phase and magnitude data, and using SMART (Susceptibility Mapping and Phase Artifacts Removal Toolbox, Detroit, Michigan, USA) software. The length and susceptibility of the MCA thrombus were measured using SPIN (Signal Processing in Nuclear Magnetic Resonance, Detroit, Michigan, USA) software (Fig. 1), and the thrombus length in SWIM images was kept the same as that in SWI images. The thrombus segment (single or multiple segments), length, susceptibility, and clot burden score (CBS) were recorded. The DWI-Alberta Stroke Program Early CT score (DWI-ASPECTS) was measured to estimate the size of cerebral infarction. The NIHSS scores were also assessed. The differences in thrombus length, thrombus susceptibility, CBS, DWI-ASPECTS, and NIHSS scores in the groups with/without DMVs or in the groups with/without APCVs were explored using two independent sample t-tests and the Mann-Whitney U test. The difference in the presence of APCVs between the group with/without DMVs was explored using a chi-square test.

Results

The DWI-ASPECTS scores of the different groups are shown in Table 1. The admission NIHSS scores in the APCVs group were significantly higher than those in the non-APCVs group (P=0.025). There was no statistically significant difference in DWI-ASPECTS and discharged NIHSS scores between APCVs group and non-APCVs group (P>0.05) (Table 2). There was no significant difference in the thrombosis length, thrombus susceptibility, CBS scores, and the number of thrombus segments between the DMVs group and the non-DMVs group and between the APCVs group and the non-APCVs group (P>0.05) (Table 3). There was a statistically significant difference in the presence of APCVs between DMVs group and non-DMVs group (P=0.001) (Table 4). 93.8% of patients in the DMVs group had the presence of APCVs.

Discussions

We found that the DWI-ASPECTS score of the non-DMVs group was significantly higher than that of the DMVs group. We also found that the admission NIHSS scores and the discharged NIHSS scores of the DMVs group were significantly higher than those of the non-DMVs group, indicating that the presence of DMVs suggested more severe cerebral infarction. The reason may be that severe cerebral infarction can cause total cerebral hemisphere ischemia, decreased cerebral blood velocity, and increased deoxyhemoglobin in the DMVs⁴, all of which can increase the clarity of the DMVs. In our study, we found that admission NIHSS scores in the APCVs group were significantly higher than those in the non-APCVs group, suggesting that the presence of APCVs also correlated with more severe cerebral infarction. The mechanism underlying the presence of APCVs may be that ischemic brain tissue results in decreased cerebral blood velocity and increased deoxyhemoglobin in the cortical veins^{1, 5}. The presence of a DMV or APCV was not affected by thrombus-related burden factors, such as the thrombus length, thrombus susceptibility, CBS scores, or the number of thrombosis segments.

Conclusions

The presence of DMVs indicates a larger size of cerebral infarction and increased discharged NIHSS score, suggesting poor short-term prognosis.

Acknowledgements

The contribution of each author to the work was listed as followed: Shuang Xia (S.X.): substantial contributions to conception and design; agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved; Chao Chai (C.C.): substantial contributions to conception and design, acquisition of data, or statistical analysis and interpretation of data; Qingyuan Yang(Q.Y.Y.): contributions to conception and design; acquisition of data, or analysis and interpretation of data; Sile Hu(S.L.H.): acquisition of data, or analysis and interpretation of data; Tianyi Qian (T.Y.Q.): analysis and interpretation of data; E Mark Haacke (E.M.H.): substantial contributions to conception and design; analysis and interpretation of data; revising it critically for important intellectual content; Wen Shen (W.S.): substantial contributions to conception and design.