AbstractObjectivePsychogenic non‐epileptic seizures (PNES) are functional neurological disorders that are often misdiagnosed and treated as epileptic seizures (ES). Video‐electroencephalography (v‐EEG) is the gold standard for differentiating ES from PNES. However, blood biomarkers provide a faster and more accessible methodology, particularly for unwitnessed events. Ubiquitin C‐terminal hydrolase L1 (UCH‐L1) and protein S100B are key biomarkers released following neuronal and glial damage. Previous experimental and clinical studies have shown increased postictal serum and cerebrospinal fluid (CSF) levels of UCH‐L1 and S100B in patients with ES.MethodsThis prospective cohort pilot study compared postictal serum levels of UCH‐L1 and S100B proteins in subjects with ES to those with PNES, aiming to identify specific biomarkers for distinguishing these conditions. To exclude confounding factors, the inclusion criteria required normal magnetic resonance (MR) findings of the brain. Strict timing of blood sampling and v‐EEG monitoring were used for diagnosing PNES. The study included 32 subjects with epilepsy, 36 with PNES, and 30 healthy controls.ResultsA significant difference in postictal UCH‐L1 levels was observed among the groups. Subjects with ES had significantly higher postictal UCH‐L1 levels (pg/mL) compared to those with PNES (p = 0.049) and healthy controls (p = 0.029). No significant differences were found between PNES subjects and healthy controls (p = 0.756). Postictal protein S100B levels did not differ significantly between the groups (p = 0.515).SignificanceThis study confirms the potential of postictal UCH‐L1 levels as a biomarker for distinguishing ES from PNES. However, it also raises questions about the utility of protein S100B as a biomarker in epilepsy. Given the pilot nature of this study, UCH‐L1 cannot yet be adopted for clinical use due to the small sample size, as statistical significance may have been driven by a subset of eight patients.Plain Language SummaryThis study evaluated two potential biomarkers, UCH‐L1 and S100B, to differentiate ES from PNES in clinical practice. Our findings showed elevated postictal UCH‐L1 levels in subjects with epilepsy compared to those with PNES, while no significant differences in S100B levels were observed among the groups.