NEFL and frontotemporal dementia: Examples of the diagnostic utility of NfL is its ability to differentiate between idiopathic Parkinson's disease and atypical parkinsonian syndromes,5,9 as well as between primary psychiatric syndromes and frontotemporal dementia, where levels are roughly five-fold higher.9,27 However, as with most clinical chemistry analyses, changes due to the normal biology exist also for NfL.