Longitudinal measurement of cerebrospinal fluid neurofilament light in anti‐N‐methyl‐D‐aspartate receptor encephalitis

BACKGROUND AND PURPOSE: Biomarkers reflecting the course of patients suffering from anti‐N‐methyl‐D‐aspartate receptor encephalitis (anti‐NMDARE) are urgently needed. Neurofilament light chains (NfL) have been studied as potential markers for neuroaxonal injury mainly in neuroinflammatory diseases, but so far there have been only in a few small reports on anti‐NMDARE. We aimed to compare the longitudinal course of cerebrospinal fluid (CSF)‐NfL levels and anti‐N‐methyl‐D‐aspartate receptor (anti‐NMDAR) antibodies with clinical parameters in six patients with anti‐NMDARE. METHODS: Longitudinal measurement of CSF‐NfL levels and CSF anti‐NMDAR antibodies in six patients suffering from anti‐NMDARE was performed. RESULTS: The major finding of this study is that most of our patients showed highly elevated NfL, with peak levels considerably delayed to clinical nadir. High NfL levels were associated with hippocampal atrophy but not with tumors detected. Furthermore, we did not find a clear relationship between NfL levels, CSF antibody titer, and CSF inflammatory markers. CONCLUSIONS: CSF‐NfL levels do not predict short‐term outcome but rather are associated with intensive care unit stay and extreme delta brushes. However, high CSF‐NFL levels were associated with long‐term outcome. Our data suggest early aggressive immunotherapy to avoid primary and secondary neuroaxonal damage.