Serum S100B and Clinical Outcomes After Spontaneous Subarachnoid Hemorrhage: A Prospective Observational Study

This study aims to investigate the prognostic value of serum S100B protein in patients with spontaneous subarachnoid hemorrhage (sSAH), specifically in predicting mortality and functional outcomes. A prospective observational study was conducted on 108 consecutive sSAH patients admitted between January 2022 and August 2024. Serum S100B levels were measured at 24 h (T0), 72 h (T1), and 7 days (T2) post-admission. Clinical outcomes, including the modified Rankin Scale (mRS) at 14 days and 3 months, as well as complications such as delayed cerebral ischemia (DCI) and systemic adverse events, were recorded. Associations were analyzed using logistic regression and explored using random forest with repeated cross-validation. Higher early S100B levels were independently associated with worse functional outcome and higher mortality. S100B at T1 was associated with delayed cerebral ischemia (DCI) in univariate analysis, but this association did not persist after multivariable adjustment for clinical severity. Random forest analyses supported the prognostic value of early S100B measurements for functional outcome; S100B at T0 and T1 emerged as the most influential predictors. No significant association was found between S100B levels and systemic complications. S100B is a promising early biomarker for predicting mortality and functional outcomes in sSAH, whereas its independent association with DCI and its predictive value for systemic complications appear limited. Larger validation studies are warranted before biomarker-guided clinical protocols can be considered.