NEFL and primary progressive aphasia: Thus, for frontal forms of AD (e.g., primary progressive logopenic aphasia), the measurement of NfL could be of interest in the differential diagnosis with other primary progressive aphasias and, more generally, with frontotemporal lobar degeneration (FTLD), where NfL levels are higher (Pijnenburg et al., 2015; Disanto et al., 2016; Steinacker et al., 2017a; Paterson et al., 2018; Lleó A et al., 2019).