Objective To explore the risk factors,mechanism and treatment strategies of secondary brain injury (cerebral hemorrhage or cerebral infarction/encephaledema) adjacent to acute epidural hematoma after surgical evacuation.Methods Forty-four patients with acute epidural hematoma underwent craniotomy in our hospital from March 2013 to December 2018 were chosen in this study.According to postoperative CT or MR imaging examination results,patients were divided into group of secondary brain injury (n=11) and group of non-secondary brain injury (n=33).The clinical data of the two groups were compared,and the significance of epidural hematoma thickness in assessing secondary brain injury was analyzed by receiver operating characteristic (ROC) curve.Binary Logistic regression analysis was used to analyze the independent risk factors affecting secondary brain injury.Results After surgery,11 showed secondary brain injury:3 occurred cerebral hemorrhage,one of whom was diagnosed as having cerebral venous hemorrhage in the cortical vein drainage area caused by traumatic cerebral venous circulation disorder;6 had cerebral infarction/encephaledema,and 2 occurred hemorrhagic cerebral infarction/encephaledema;two underwent secondary craniotomy and both achieved satisfactory effect.As compared with patients from the non-secondary brain injury group,patients fromsecondary brain injury group had significantly higher percentage of patients with epidural hematoma thickness ≥ 33.5 mm (P＜0.05).ROC curve analysis showed that the thickness of epidural hematoma had predictive value in secondary brain injury after surgery (P＜0.05),and area under the curve was 0.722 and diagnostic threshold was 33.5 mm.Binary Logistic regression analysis revealed that epidural hematoma thickness ≥33.5 mm was an independent risk factor for secondary brain injury adjacent to epidural hematoma after surgery (odds ratio=7.367,P=0.024,95％CI=1.298-41.797).Conclusions Acuteepidural hematoma thickness ≥33.5 mm is a high-risk factor associated with secondary brain injury adjacent to epidural hematoma after surgery.Intracranial venous circulatory disorders have non-negligible effect on occurrence of secondary brain injury.