Abstract： Objective:To explore the correlation between decreased cerebral perfusion measured from arterial spin labeling and cerebrovascular events in patients with bilateral moyamoya angiography (MMA).Methods:Twenty-seven consecutive cases with bilateral MMA, who were admitted to the neurosurgery department of Nanjing Drum Tower Hospital from April to November 2020, were included in this retrospective study. Among them, 10 were males and 17 were females, aged 35-66 (55±9) years. These patients all presented with unilateral cerebral hemisphere cerebral infarction or cerebral hemorrhage. The Wilcoxon paired signed-rank test was used to qualitatively analyze the differences in the Arterial Transit Artifact (ATA) of the bilateral cerebral hemispheres. The mean gray value, the kurtosis and skewness of gray distribution curve of bilateral cerebral hemispheres on cerebral blood flow (CBF) images with post labeling delay (PLD) of 1.5 s and 2.5 s were quantitative calculated. The relationship between ASL and cerebrovascular event was determined using binary logistics regression analysis.Results:No significant difference was observed in ATA between bilateral hemispheres on CBF images with PLDs of 1.5 s and 2.5 s ( P>0.05). On the CBF images with a PLD of 1.5 s, the mean gray value of the cerebral hemisphere on the lesion side (17.50±5.88) was markly lower than that on the non-lesion side (20.80±5.51) ( P<0.001), the kurtosis and skewness of gray distribution were significantly different between bilateral cerebral hemispheres ( P<0.05);On the CBF images with a PLD of 2.5 s, the mean gray value and the skewness of the gray distribution on the lesion side of the cerebral hemisphere were statistically different from those on the non-lesion side ( P<0.05), while the difference in kurtosis was not statistically significant between bilateral cerebral hemispheres ( P>0.05). Multivariate regression analysis showed that the reduction of gray value on the side of the lesion was independently associated to the occurrence of the cerebrovascular events ( ORPLD1.5=0.192, 95% CI:0.047-0.783; ORPLD2.5=0.175, 95% CI:0.050-0.615). Conclusion:The decreased perfusion detected by ASL is independently associated with cerebrovascular events in patients with MMA.