Objective To investigate the relationship between the numbers of deep medullary veins (DMV) beside the ipsilateral lateral ventricle and the stenotic degree of large artery of ipsilateral internal carotid artery (ICA) system and cerebrovascular reactivity (CVR) in patients with acute cerebral infarction showed on susceptibility-weighted imaging (SWI) in middle cerebral artery (MCA) territory.Methods The patients with acute cerebral infarction in MCA territory who underwent SWI,cerebral angiography and the transcranlal Doppler carbon dioxide challenge test during the hospital stay were enrolled retrospectively.According to the numbers of DMV beside the lateral ventricle on SWI,they were classified into 3 grades:Grade 1:DMV ＜5; Grade 2:DMV 5-10; Grade 3:DMV ＞ 10.The correlations of the DMV grades and the degree of ipsilateral ICA/MCA and CVR were analyzed.Results A total of 44 patients with acute cerebral infarction in MCA territory were enrolled.Twenty-four patients were DMV 1,15 were DMV2,and 5 were DMV 3.The mean stenosis degree of the main arteries of the ipsilateral ICA system was 40.52％ ±30.62％.The mean CVR of MCA was 0.41 ± 0.16.The stenosis degrees in the DMA grade 1,2,and 3groups were 31.31％ ± 26.02％,44.93％ ± 31.03％,and 71.76％ ± 26.68％,respectively.There were significant differences among the 3 groups (F=4.589,P =0.018),and the stenosis degree in the DMV grade 3 group was significantly higher than that in the DMV grade 1 group (P=0.014).The CVRs in the grade 1,2,and 3 groups were 0.45 ± 0.12,0.41 ± 0.18,and 0.22 ± 0.12,respectively.There were significant differences among the 3 groups (F=6.179,P=0.005),and the CVR in the DMV grade 3 group was significantly lower than that in the DMV grade 1 group (P =0.006) and in the DMV grade 2 group (P =0.038).Spearman correlation analysis showed that DMV grade was significantly positively correlated with the stenosis degree (rs =0.381,P =0.013),and was significantly negatively correlated with CVR (rs =-0.375,P=0.012).Conclusions The DMV grade in patients with cerebral infarction was positively correlated with the stenosis degree of responsible large artery and was negatively correlated with the MCA CVR in the responsible side.