The multifaceted role of neurofilament light chain protein in non-primary neurological diseases.

The advancing validation and exploitation of cerebrospinal fluid and blood neurofilament light chain protein as a biomarker of neuroaxonal damage has deeply changed the current diagnostic and prognostic approach to neurological diseases. Further, recent studies have provided evidence of potential new applications of this biomarker also in non-primary neurological diseases. In the present review we summarise the current evidence, future perspectives, but also limitations, of neurofilament light chain protein as a cerebrospinal fluid and blood biomarker in several medical fields, including intensive care, surgery, internal medicine and psychiatry. In particular, neurofilament light chain protein is associated with the degree of neurologic impairment and outcome in patients admitted to intensive care units or in the perioperative phase and it seems to be highly interconnected with cardiovascular risk factors. Beyond that, interesting diagnostic and prognostic insights have been provided by the investigation of neurofilament light chain protein in psychiatric disorders as well as in the current coronavirus disease 19 (COVID-19) pandemic and in normal aging. Altogether, current data outline a multifaceted applicability of cerebrospinal fluid and blood neurofilament light chain protein ranging from the critical clinical setting to the development of precision medicine models suggesting a strict interplay between the nervous system pathophysiology and the health-illness continuum.