NfL as Analogue of C-Reactive Protein in Neurologic Diseases

In the past decade, clinical research in neurologic diseases has been boosted by the possibility to quantify the degree of neuronal damage through easy-to-collect blood samples. Ultrasensitive immunoassays, such as the single-molecule array, have made it possible to measure the light chain of neurofilaments (NfL), a protein of exclusively neuronal origin, in serum and plasma, where its concentrations are roughly 40-fold lower compared with CSF.1 This sentinel of neuronal damage has been shown to detect the presence of a variety of CNS diseases, from multiple sclerosis to Alzheimer disease, frontotemporal dementia, motor neuron diseases, parkinsonism, cerebrovascular disease, and traumatic brain injury.1 Due to its ability to reflect the dynamic nature of CNS injuries, NfL has been called the “C-reactive protein” of neurology.2 Studies on blood NfL dynamics in the preclinical phases of neurologic diseases show that the signs and symptoms used to make clinical diagnoses appear late in the disease course in relation to when the pathology starts and ultrasensitive serum NfL levels can be used to identify diseases at an earlier stage.3