Prediction of Postoperative Recurrence of Chronic Subdural Hematoma Using Preoperative Systemic Immune Inflammation Index and Eosinophils

<b>Objective</b> Chronic subdural hematoma (CSDH) is a common neurological problem with significant recurrence after surgery. Risk considerations can vary, ranging from patient-related factors to those related to the surgical procedure. This study explores the association between preoperative eosinophil count and systemic immune inflammation (SII) with CSDH recurrence. <b>Materials and Methods</b> We conducted a prospective analysis of 105 patients with equal numbers of CSDHs who underwent surgery for CSDH between January 2023 and January 2024. The preoperative eosinophil counts, along with other differential leukocyte counts, were measured. The SII index was calculated using the standard formula (SII = neutrophil count × platelet count/lymphocyte count). Multivariate and univariate regression analyses were performed to assess the association between risk factors and CSDH recurrence. <b>Results</b> The preoperative eosinophil count showed a significant correlation with recurrence ( <i>p</i> < 0.001). The SII index was significantly higher in patients with recurrent CSDH ( <i>p</i> = 0.003). Neutrophils were found to be significantly associated with CSDH recurrence ( <i>p</i> = 0.038). Age ( <i>p</i> < 0.001) and SII ( <i>p</i> = 0.005) were found to be independent predictors of CSDH recurrence, whereas hematoma volume ( <i>p</i> < 0.001) and the antiplatelet regimen were a significant predictor of CSDH recurrence ( <i>p</i> = 0.047). Variables like male gender, diabetes mellitus, anticoagulants, and hematoma volume were associated with eosinophil-rich or eosinophil-poor status. <b>Conclusion</b> Preoperative eosinophil count, neutrophils, and the SII index may serve as potential predictors of CSDH recurrence. Further studies with larger sample sizes are needed to validate these findings.