Olsson B, et al. - In this case-control study with 913 participants, researchers examined cerebrospinal fluid (CSF) levels of neurofilament light (NFL) protein (a marker of neuroaxonal degeneration) in control participants and patients with dementia, motor neuron disease, and parkinsonian disorders, and identified its association with longitudinal cognitive decline. Between control participants, participants with mild cognitive impairment, and those with Alzheimer disease, a stepwise increase in cerebrospinal fluid neurofilament light (CSF NFL) levels were observed, showing that NFL levels rise with increasing cognitive impairment. In patients with Alzheimer disease and frontotemporal dementia, levels of CSF NFL were related to cognitive impairments. NFL levels seem to mirror intensity of the neurodegenerative processes in other neurodegenerative disorders. In frontotemporal dementia, amyotrophic lateral sclerosis, and atypical parkinsonian disorders, the highest levels were seen.