Nomenclature

FTD nomenclature has evolved rapidly as our scientific understanding has improved. The term "frontotemporal dementia" (FTD) is used to refer to the clinical syndromes, such as behavioral variant FTD (bvFTD), nonfluent/agrammatic variant PPA (NFAV-PPA), and semantic variant PPA (SV-PPA). These syndromes are united by involvement of frontal and temporal brain regions. Previously, researchers sometimes used “FTD” to refer only to bvFTD, which has also been called "frontal variant FTD" (fvFTD).

FTD language variants are sometimes grouped under the umbrella term "primary progressive aphasia" (PPA). PPA has now been split into three subgroups: nonfluent/agrammatic variant PPA (NFAV-PPA, also known as progressive nonfluent aphasia (PNFA) and agrammatic PPA or PPA-G), semantic variant PPA (SV-PPA, also known as semantic dementia (SD) or PPA-S), and logopenic variant PPA (LV-PPA, also known as logopenic progressive aphasia (LPA) and logopenic PPA or PPA-L). Patients with LV-PPA are often found to have Alzheimer’s disease at autopsy. SV-PPA was previously referred to at times as "temporal variant FTD" (tvFTD).

Motor presentations of FTD include FTD with motor neuron disease (FTD-MND), corticobasal degeneration (CBD) – also sometimes referred to as corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP).

The term "frontotemporal lobar degeneration" (FTLD) is used to describe the specific pathological diseases that result in FTD syndromes. These too are united by their impact on frontal and temporal brain structures. Subtyping is based on the specific proteins found within neuronal inclusions. Most FTLD subtypes are either

1. FTLD-tau, which includes Pick’s disease, CBD and PSP, all of which show tau-containing inclusions or
2. FTLD-TDP, which includes several subtypes in which TDP-43 containing inclusions are seen.