Both NfL and NfH CSF levels are increased in MS patients, however, this is not specific to MS: NfL levels are also increased in other neurodegenerative diseases, such as prion diseases, amyotrophic lateral sclerosis, Alzheimer’s disease, Parkinson’s disease, Hungtington’s disease, and traumatic brain injuries, and they can be influenced by other confounding effects, such as age or non-neurological comorbidities. This evidence concerns the gene NEFL and prion disease.