Abstract: Objective · To analyse the relating factors that influence the prognosis of chronic subdural hematoma(CSDH) after drilling drainage and to explore the bilateral bleeding risk factors of CSDH. Methods · Four hundred and forty patients with CSDH who underwent drilling drainage were retrospectively analysed. Clinical data, including medical history, signs, blood coagulation function and imaging examination were collected. Spearman correlation analysis and ordinal Logistic regression analysis were performed to assess the relationships between various variables and the prognosis, and univariate analysis and multivariate Logistic regression analysis were performed to explore the risk factors that lead to the occurrence of bilateral bleeding. Results · Spearman correlation analysis indicated that age, medication history of anticoagulant drugs, bilateral hematoma or not, the thickness of the hematoma and volume of intracranial gas on the first post-surgery day and preoperative Markwalder grade were associated with postoperative Markwalder grade (P<0.05). Ordinal Logistic regression analysis showed that medication history of anticoagulant drugs and preoperative Markwalder grade were the independent risk factors (P0.028, P0.000). Univariate analysis of the bilateral bleeding indicated that age, medication history of anticoagulant drugs and thrombin time were statistically different between unilateral and bilateral CSDH (P<0.05). Multivariate Logistic regression analysis revealed that thrombin time was the independent risk factor (OR1.147, 95%CI 1.005-1.309, P0.042). Conclusion · Age and medication history of anticoagulant drugs were closely related to the bilateral chronic subdural hematoma. The higher the preoperative Markwalder grade is, the higher the postoperative Markwalder grade is. The prognosis of patients without anticoagulant drugs is better than those users.

Key words: chronic subdural hematoma, bilateral bleeding, risk factors, prognostic analysis