Do Serum Brain Biomarkers Differentiate the Hemorrhagic Head Injury Lesion Phenotypes? An Interim Analysis of an On-Going Randomized Clinical Trial

<b>Background</b>: Traumatic head injury (THI) includes a diverse range of hemorrhagic brain lesions (HBL), which are distinct phenotypes with characteristic pathophysiological mechanisms. Computed tomography (CT) is the cornerstone of the initial assessment and diagnosis; however, its sensitivity is limited, especially in mild head injury. Blood-derived biomarkers, including Neuron-Specific Enolase (NSE) and S-100B, have been extensively studied; however, their efficacy in distinguishing HBL subtypes remains unclear. We evaluated whether circulating serum levels of S-100B and NSE can discriminate between distinct intracranial HBLs and extracranial hemorrhagic lesions (ECH). <b>Methods</b>: This is an interim analysis of a prospective, randomized, double-blind clinical trial including 434 adult patients with blunt THI. HBL phenotypes identified by CT scan included subarachnoid hemorrhage (SAH), subdural hematoma (SDH), epidural hematoma (EDH), and brain contusion (BC). Unique lesions were considered while overlapping lesions were excluded. Subgaleal hematoma (SGH) was included as an example of ECH. Serum S-100B was assessed within 6 h post-injury, while serum NSE was evaluated at admission, 24 h, and 48 h thereafter. Serum NSE and inflammatory cytokines were quantified in duplicates using a Human Magnetic Luminex 5-plex assay, while serum S-100B concentrations were measured separately. Serum epinephrine concentrations were quantified using an ELISA. Biomarker profiles were analyzed based on lesion phenotype, lesion multiplicity, injury pattern, and clinical outcomes, including hospital length of stay (HLOS) and the Glasgow Outcome Scale-Extended (GOSE). <b>Results</b>: Admission median S-100B levels were higher in patients with SAH (495 pg/mL) and lower in those with SGH (191 pg/mL); however, they did not show statistically significant difference among HBL phenotypes. They were significantly higher in patients with polytrauma TBI (420 pg/mL) compared to isolated TBI (258 pg/mL). Baseline and 48 h NSE concentrations were significantly higher in SDH (25,089 and 28,438 pg/mL) than in other THI lesions (<i>p</i> = 0.04). There were no statistically significant changes in NSE values over time across all THI lesions except for SDH in which they raised more after 48 h (<i>p</i> = 0.02). They had a significant drop in polytrauma over the time (<i>p</i> = 0.001). Compared to intracranial lesions, S-100 B levels were significantly lower in SGH and in skull fractures without intracranial hematomas. Both S-100B and NSE levels were elevated in individuals with unfavorable GOSE scores. <b>Conclusions</b>: In this secondary exploratory analysis, elevated serum NSE and S-100B levels discriminate between extra- and intracranial lesions and appear to represent distinct but complementary aspects of THI, indicating neuronal damage and its temporal evolution, and predicting clinical and functional outcomes. The present findings reflect association and not causation. Future studies incorporating larger or multicenter cohorts, volumetric imaging, and long-term outcomes are required to validate and refine biomarker-guided algorithms for personalized THI care.