Background and Purpose—Collateral flow compensation followed by cerebrovascular stenosis is closely correlated to acute ischemic stroke (AIS) and chronic cerebral hypoperfusion. Many evidences indicated that diabetes mellitus (DM) probably had impact on it, but the exact extent was unclear. Aim of this study is to investigate the impact of DM on collateral flow of patients with severe stenosis or occlusion of middle cerebral artery (MCA). Methods—We retrospectively identified patients from our

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... egistry of patients who had severe stenosis or occlusion in the MCA diagnosed by digital substraction angiography (DSA), besides it, collateral flow compensation was also assessed by magnetic resonance perfusion (MRP). Relative parameters of perfusion (MTT, TTP, CBF, CBV) in the different areas including Am, Lm, Pm, Bm were compared between diabetic and non-diabetic patients. Based on this background, multivariable logistic regression was used to identify the independent correlation between DM and above MRP values with obvious difference, so did the correlation between they and HbA1c or fasting blood glucose (FBG) through Spearman correlation coefficient. Results—105 patients were included in this study, with 73 patients belong to non-diabetes mellitus (NDM) group and 32 patients belong to DM group. Older age, higher fibrinogen (FIB) and fasting blood glucose (FBG), higher percent of hypertension were seen in the DM group compared to the NDM group. Higher ipsilateral/contralateral ratio of CBF and CBV in Lm area was observed in DM group in contrast with NDM group, and lower ipsilateral/contralateral ratio of MTT was observed in DM group in Am and Lm areas, so did TTP in Lm and Pm areas. Independent correlation was also maintained between DM and Lm-CBF, Lm-CBV, Lm-MTT, Lm-TTP, Am-MTT, Pm-TTP through multivariable logistic regression. Both FBG and HbA1c were correlated to part of above parameters of ipsilateral/contralateral ratio, while the impact of FBG was more prominent. Conclusions—DM can partly improve cerebral hypoperfusion due to severe stenosis or occlusive in the MCA, which is probably originated from microvascular remodeling induced by pre-existence of DM.