Neurofilament changes in serum and cerebrospinal fluid after acute ischemic stroke

Background: Neurofilament light (NFL) is a well-validated biomarker for neuronal injury and neurodegeneration. Increased cerebrospinal fluid (CSF) levels have been shown after stroke, as well as in patients with a broad range of neurodegenerative and neuroinflammatory diseases. Neurofilament heavy (NFH) belongs to the same family of structural proteins but it is less extensively studied. The potential of phosphorylated NFH (pNFH) as a stroke biomarker and for the prediction of clinical outcome is unknown. In this study, we aimed to examine the temporal pattern of NFL and pNFH concentrations in serum and CSF after acute ischemic stroke. Materials and Methods: A quantitative Enzyme-Linked ImmunoSorbent Assay (ELISA) for pNFH was developed and tested on CSF and serum samples. NFL and pNFH were analysed in serum and CSF of acute ischemic stroke patients, who were followed over time (Day 0-1, Day 2-3, Day 7-9, three weeks, and 3-5 months after stroke). Results: NFL and pNFH concentrations in serum and CSF increased after stroke, peaked during the 3rd week, and then decreased back to almost baseline levels at 3-5 months. CSF-NFL and serum-NFL correlated to the outcome measured by Barthel Index after 3-5 months, whilst no such association was seen for pNFH. Discussion: These findings suggest that NFL and pNFH in both CSF and serum reflect the temporal pattern of the post ischemic axonal injury and that this process does not seem to progress after 3-5 months. Conclusion: NFL and pNFH in CSF and serum are promising biomarkers for axonal injury following stroke. Further studies in larger populations are needed to fully understand the progression of the neuronal damage after acute ischemic stroke and to evaluate if these biomarkers can provide additive information and how they relate to outcome.