While the turnover of Nf-L in normally aging brains is slow, abnormally elevated levels of Nf-L in CSF and blood have been associated with several neurodegenerative conditions such as multiple sclerosis (MS), various types of dementia such as Alzheimer’s disease (AD) and frontotemporal dementia (FTD), and several other neurodegenerative diseases [4,6,8]. This evidence concerns the gene NEFL and early-onset autosomal dominant Alzheimer disease.