Sechi E, Mariotto S, McKeon A, et al. - This study was undertaken to determine if the ratio between serum neurofilament light chain levels and MRI T2-lesion area (neurofilament light chain/area ratio—NAR) can discriminate spinal cord infarction (SCI) from acute myelitis of similar severity. Mayo Clinic patients (January 1, 2000–December 31, 2019) were retrospectively identified with SCI, AQP4 (aquaporin 4)-IgG, or MOG (myelin oligodendrocyte glycoprotein)-IgG-associated myelitis at disease clinical presentation, or idiopathic transverse myelitis from a previously identified population-based cohort of patients seronegative for AQP4-IgG and MOG-IgG. Participants in the study were 48 patients. In patients with SCI, serum neurofilament light chain levels were significantly higher vs patients with AQP4-IgG-associated myelitis, MOG-IgG-associated myelitis, and idiopathic transverse myelitis. With 86% specificity and 95% sensitivity, NAR showed the greatest accuracy for identification of SCI vs acute myelitis with values ≥0.35 pg/(mL·mm2). Data reported that the positive and negative likelihood ratios, respectively, were 6.67 and 0.06. NAR remained independently linked to SCI after adjusting for age, gender, immunotherapy before sampling, and days from myelopathy symptoms onset to sampling. For differentiation of SCI from acute myelitis, NAR is a novel and promising clinical biomarker.