Neurofilament Light Chain (NfL) is an important structural component of the neuronal cytoskeleton. It is released into the cerebrospinal fluid (CSF) and blood following neuronal injury and degeneration in a range of neurodegenerative disorders, including multiple sclerosis (MS), amyotrophic lateral sclerosis, Alzheimer's disease, Guillain-Barré syndrome, and Huntington disease.
Based on how well NfL levels in blood and CSF correlate with MS disease activity, it has been proposed as a biomarker for neurologic damage and disease activity in relapsing MS (Thebault et al. 2021, and references therein).