NEFL and neurodegenerative disease: NfL constitutes a part of the neuronal cytoskeleton and shows promise in evaluating acute and chronic severity and the course of neurodegenerative diseases, such as Alzheimer disease, Parkinson disease, and multiple sclerosis,1,2,3 as well as hypoxic and traumatic brain injuries.4,5 Data on NfL in the preterm infant are sparse.