NEFL and frontotemporal dementia: NfL may also be useful for predicting symptom onset in genetic neurodegenerative conditions such as frontotemporal dementia [19], genetic Creutzfeldt-Jakob disease [17], or genetic amyotrophic lateral sclerosis [20], although it is still unclear when increased levels can first be detected in these different disorders and whether NfL rises in the asymptomatic phase of each disease or only with symptom onset.