Longitudinal Kinetics of Cerebrospinal Fluid and Serum S100B in Patients with Delayed Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage

S100 calcium-binding protein B (S100B) has been proposed as a biomarker of brain injury after aneurysmal subarachnoid hemorrhage (aSAH), although the clinical utility of serial measurements remains uncertain. This prospective observational study investigated whether longitudinal serum and cerebrospinal fluid (CSF) S100B concentrations are associated with delayed cerebral ischemia (DCI), inflammatory activation, and neurological outcome. Twenty-six consecutive patients with aSAH underwent serial serum and CSF S100B measurements throughout hospitalization. Associations between S100B concentrations, DCI, disease severity, inflammatory biomarkers, and 3-month neurological outcome were analyzed. Admission serum S100B concentrations were significantly higher in patients who subsequently developed DCI (152.6 vs. 21.0 ng/L, p = 0.012) and correlated with disease severity and inflammatory biomarkers. Admission serum S100B was associated with DCI and showed good discriminative ability for DCI (AUC 0.79) and unfavorable 3-month outcome (AUC 0.86). Longitudinal analyses showed persistently elevated serum S100B concentrations in patients who developed DCI, while serum and CSF S100B exhibited similar temporal profiles throughout the observation period Serial serum S100B measurements appear to reflect the temporal evolution of secondary brain injury after aSAH and may provide complementary biological information alongside established clinical assessment.