Neurofilament Light Chain and Multiple Sclerosis: Building a Neurofoundational Model of Biomarkers and Diagnosis.

Neurofilament light chain (NfL), an abundant cytoskeletal protein in neurons, has emerged as a promising serum biomarker that indicates non-specific neuronal damage secondary to various neurologic diseases, including multiple sclerosis (MS). Emerging evidence suggests that serum NfL levels correlate with future disability, brain atrophy, predict new disease activity, and decrease in response to various disease-modifying therapies. As research continues to validate NfL's potential role in clinical practice, the need for a practical model to conceptualize and visualize its relevance to MS pathology becomes evident-not only for healthcare providers but also for patients. To address this, we propose the Neurofoundational Model (NFM), which likens a neuron to a home, with various parts of the home representing distinct regions of the central nervous system (CNS). In this model, the home (neuron) experiences scenarios such as a fire, an earthquake, and a slow flood, representing distinct MS disease states. A fire illustrates an MS relapse with good recovery, where serum NfL levels rise during the relapse and subsequently return near baseline. An earthquake represents an MS relapse with poor recovery, where NfL levels increase and remain elevated above baseline. Finally, a slow flood depicts MS in progressive stages, characterized by sustained and gradually increasing serum NfL levels without abrupt clinical changes. This approach offers a clear and relatable visualization for clinicians and patients alike, illustrating the dynamics of serum NfL levels during CNS damage caused by demyelination. By integrating this model into clinical practice, we aim to enhance understanding and communication regarding the role of NfL in MS pathology and its potential utility as a biomarker.