Serum neurofilament light chain is a biomarker of acute and chronic neuronal damage in early multiple sclerosis

Background: Monitoring neuronal injury remains one key challenge in early relapsing-remitting multiple sclerosis (RRMS) patients. Upon axonal damage, neurofilament - a major component of the neuro-axonal cytoskeleton - is released into the cerebrospinal fluid (CSF) and subsequently peripheral blood. Objective: To investigate the relevance of serum neurofilament light chain (sNfL) for acute and chronic axonal damage in early RRMS. Methods: sNfL levels were determined in 74 patients (63 therapy-naive) with recently diagnosed clinically isolated syndrome (CIS) or RRMS using Single Molecule Array technology. Standardized 3 T magnetic resonance imaging (MRI) was performed at baseline and 1-3 consecutive follow-ups (42 patients; range: 6-37 months). Results: Baseline sNfL correlated significantly with T2 lesion volume (r = 0.555, p < 0.0001). There was no correlation between baseline sNfL and age, Expanded Disability Status Scale (EDSS) score or other calculated MRI measures. However, T2 lesion volume increased (r = 0.67, p < 0.0001) and brain parenchymal volume decreased more rapidly in patients with higher baseline sNfL (r = -0.623, p = 0.0004). Gd-enhancing lesions correlated positively with sNfL levels. Initiation of disease-modifying treatment led to a significant decrease in sNfL levels. Conclusion: sNfL indicates acute inflammation as demonstrated by correlation with Gd+ lesions. It is a promising biomarker for neuro-axonal damage in early multiple sclerosis (MS) patients, since higher baseline sNfL levels predicted future brain atrophy within 2 years.