Risk Factors of Chronic Subdural Hematoma Recurrence: A Systematic Review.

Background: Although various factors have been proposed in connection with the recurrence of chronic subdural hematoma (cSDH), the results obtained in previous studies have not been consistent. This study was conducted to describe the risk factors for cSDH recurrence, drawing upon the current literature, and to provide an integrative framework that links these factors with underlying biological mechanisms. Methods: In December 2024, a systematic literature search was performed using the Scopus, Web of Science, PubMed, and Embase electronic databases. The retrieved records were screened against eligibility criteria and selected in 2 stages. The Newcastle-Ottawa Scale (NOS) was utilized for bias assessment, and the PRISMA (Preferred Reporting Items for Systematic Reviews) checklist was employed to assess the methodological rigor and reliability of the selected studies and their findings. Results: After applying the inclusion and exclusion criteria, 61 studies were retained for the systematic review. The principal risk factors associated with the recurrence of cSDH were elucidated and correlated with underlying pathophysiological processes. Lower Glasgow Coma Scale (GCS) scores and elevated postoperative neutrophil counts indicate increased inflammation. The use of antiplatelet and anticoagulant agents reflects coagulation dysfunction, which raises the risk of rebleeding. Additional factors such as male sex, older age, larger hematoma size, and shorter drainage duration relate to anatomical and clinical vulnerability. Radiological signs, such as high hematoma density and midline shift, support the role of structural brain changes. Comorbidities, including diabetes and hypertension, exacerbate vascular fragility, increasing recurrence risk. Early detection, effective postoperative drainage, and higher serum HDL levels contribute to a reduced risk of recurrence. Conclusion: cSDH recurrence results from the complex interplay of biological processes, including inflammation, coagulation dysfunction, and structural brain changes, with clinical risk factors. Recognizing and targeting these integrated pathways is crucial for improving prevention and management strategies.