Circulating blood biomarkers after traumatic brain injury: A subanalysis of the biperiden phase III randomized, double-blind clinical trial (NCT01048138).

OBJECTIVE: Traumatic brain injury (TBI) is a leading cause of acquired epilepsy, death, and long-term disability, yet reliable biomarkers to predict chronic sequelae such as post-traumatic epilepsy (PTE) remain limited. We evaluated the associations between circulating blood biomarkers of neuronal, glial, and synaptic injury and the subsequent development of PTE. METHODS: This prespecified subanalysis was conducted within a randomized phase III clinical trial of biperiden in adults with acute TBI. Participants were randomly assigned to receive intravenous biperiden (4 mg every 6 h for 10 days) or placebo. Serum samples collected during the acute (1-15 days) or chronic (90-270 days) post-injury periods were analyzed for total tau (t-Tau), neurofilament light chain (NfL), glial fibrillary acidic protein (GFAP), ubiquitin C-terminal hydrolase L1 (UCHL1), and synaptosomal-associated protein 25 (SNAP25) using an ultrasensitive single-molecule array (SiMoA) platform. Exploratory multivariable analyses were performed to assess associations between biomarker concentrations and PTE. RESULTS: A total of 123 patients were enrolled. Blood samples were obtained from 58 participants (60 serum samples) for biomarker analysis, with most participants contributing a single sample and only two participants providing paired samples collected at different post-injury time points. The median age was 42 years and 48 participants (82.8%) were men. Only six patients (10.3%) developed PTE during follow-up, four in the biperiden group and two in the placebo group. NfL and GFAP concentrations varied according to injury severity and sampling period. Compared with patients who did not develop PTE, those who later developed epilepsy showed descriptively lower NfL and SNAP25 and higher t-Tau, GFAP, and UCHL1 concentrations. SNAP25 was detected in serum for the first time; however, concentrations were frequently below the assay's lower limit of quantification, limiting interpretation of this biomarker and no association with epilepsy development was observed. SIGNIFICANCE: Circulating biomarkers reflecting axonal, glial, and synaptic injury provide a descriptive characterization of biological processes following TBI. Given the limited number of PTE events, these analyses are exploratory and hypothesis generating. Further studies are needed to evaluate whether blood-based biomarkers can reliably identify individuals at risk of post-traumatic epileptogenesis.