NEFL and Alzheimer disease: Other studies have reported elevated NfL levels in patients with more aggressive neurodegenerative disease entities such as progressive supranuclear palsy (a four-repeat-(4R)-tauopathy), corticobasal syndrome (distinct underlying histopathologies, including 4R-tauopathies and mixed 3/4R tauopathy of AD pathology among others) or amyotrophic lateral sclerosis [16, 33].