Prognostic Value of Systemic Immune-Inflammation Index for Early Mortality After Decompressive Craniectomy in Malignant Middle Cerebral Artery Infarction.

Objective: Malignant middle cerebral artery infarction is associated with high mortality despite decompressive craniectomy. Reliable biomarkers predicting early outcome remain limited. The aim of this study was to evaluate the prognostic significance of inflammatory biomarkers, particularly the systemic immune-inflammation index (SII), for predicting in-hospital mortality in patients undergoing decompressive craniectomy for malignant middle cerebral artery infarction. Methods: This retrospective study included 31 patients who underwent decompressive craniectomy for malignant MCA infarction between 2014 and 2024. Demographic, clinical, radiological, and laboratory variables were analyzed. Results: Overall in-hospital mortality was 61.3%. Non-survivors had significantly higher SII, neutrophil count, neutrophil-to-lymphocyte ratio, serum creatinine, and higher prevalence of hypertension and anticoagulant therapy. ROC analysis showed that SII had the highest predictive performance (AUC = 0.833). Multivariate analysis identified age, serum creatinine, NLR, SII, hypertension, and anticoagulant therapy as independent predictors of mortality. Patients aged ≥65 years had significantly higher in-hospital mortality than younger patients. Conclusions: Elevated SII is a strong independent predictor of early mortality after decompressive craniectomy and may serve as a simple and clinically applicable biomarker for risk stratification.