Bjornevik K, Munger KL, Cortese M, et al. - Researchers performed this nested case-control study to determine if serum neurofilament light chain levels are raised prior to the clinical multiple sclerosis (MS) onset. Participants were US military personnel from whom serum samples were obtained. The study sample had a mean age of 27.5 years at baseline, and 92 of 120 participants (76.7%) were males. Findings revealed that case patients with MS vs matched control individuals exhibited elevated serum levels of neurofilament light chain 6 years prior to the clinical onset. With reducing time to the case clinical onset, an increase in this difference between cases and controls was evident. A marked rise in neurofilament light chain levels was observed in relation to clinical onset. These findings are suggestive of a prodromal phase lasting many years in MS, as well as indicate the occurrence of neuroaxonal damage already during this phase.