Amyloid and Tau as cerebrospinal fluid biomarkers in anti-N-Methyl-D-aspartate receptor encephalitis

Introduction Neuroinfection is associated with the deposition of amyloid-beta (Aβ) peptides, and subsequent decrease in cerebrospinal fluid (CSF) amyloid levels. However, whether autoimmune encephalitis involves extracellular deposition of Aβ peptides in the brain is unreported. Methods We examined CSF amyloid and tau values in adults with anti-N-methyl-D-aspartate receptor encephalitis (NMDAR-E). Forty-two patients with NMDAR-E, 35 patients with viral and bacterial neuroinfections, and 16 controls were included. We measured CSF Aβ1–42 (cAβ1–42), Aβ1–40 (cAβ1–40), t-Tau (ct-Tau), and p-Tau181 (cp-Tau181) levels and assessed their efficacies regarding differential diagnosis and predicting prognosis. Results NMDAR-E patients had lower cAβ1–42 levels; however, they were higher than those of patients with bacterial meningitis. ct-Tau levels in NMDAR-E patients were lower than those in patients with neuroinfections. No changes were observed in controls. cAβ1–42 and ct-Tau were combined as an excellent marker to distinguish NMDAR-E from neuroinfections. cAβ1–42 levels in NMDAR-E patients were positively correlated with Montreal Cognitive Assessment scores. We observed an inverse relationship between cAβ1–42 levels and modified Rankin Scale scores. Patients with poor outcomes exhibited low cAβ1–42 levels and high levels of several blood parameters. cAβ1–42 was the highest quality biomarker for assessing NMDAR-E prognosis. Correlations were found between cAβ1–42 and some inflammatory indicators. Conclusion cAβ1–42 was decreased in NMDAR-E patients. cAβ1–42 levels indicated NMDAR-E severity and acted as a biomarker for its prognosis. Combining cAβ1–42 and ct-Tau levels could serve as a novel differential diagnostic marker for NMDAR-E.