In the future, when CSF analysis, amyloid PET, and possibly other neurodegenerative biomarkers and/or tracers (i.e., amyloid and/or tau) become widely available for clinical purposes, a formal comparison with FDG-PET will be needed to define a cost-effective algorithm for diagnosis in PPA and dementia in general [15, 16]. This evidence concerns the gene MAPT and primary progressive aphasia.