Cerebrospinal fluid markers of neuronal and glial cell damage in patients with autoimmune neurologic syndromes with and without peripheral malignancies Constantinescu R, Krýsl D, Andrén K, Asztély F, Bergquist F, Zetterberg H, Andreasson U, Axelsson M, Menachem EB, Jons D, Mahamud U, Malmeström C, Rosengren L, Blennow K * Corresponding author. Acknowledgments: Anna Edelvik¹, MD; Thordis Gudmundsdottir¹, MD; Björn Holmberg¹, MD, PhD; Marie-Anne Langvall¹, RN; Peter Vaghfeldt¹, MD. Abstract Autoimmune neurological syndromes (ANS) can be paraneoplastic or non-paraneoplastic. Their clinical presentation is often similar. Better biomarkers are needed to rapidly identify patients with tumors. We investigated cerebrospinal fluid (CSF) levels of commercially available markers of neuronal (neurofilament light chain = NFL, total tau protein = T-tau) and glial (glial fibrillary acidic protein) damage in patients with ANS. CSF-NFL and T-tau were increased in both paraneoplastic and non-paraneoplastic cases. Patients with malignancies had increased CSF-NFL, CSF-blood albumin ratio, and worse long-term outcome, compared with those without. CSF-NFL levels predicted long- term outcome but were not diagnostic for malignancy after age adjustment. Key words: Autoimmune neurologic syndrome, paraneoplastic neurological syndrome, non-paraneoplastic, autoimmune encephalitis, neurofilament light chain, tau protein