Table 1.

Classification of primary progressive aphasia (PPA) variants.

	LvPPA	SvPPA	NFvPPA
Clinical features	• Impaired single-word retrieval in spontaneous speech and naming • Impaired repetition of sentences and phrases Additionally, at least 3 of the following features must be present: • Phonologic errors in spontaneous speech and naming • Spared single-word comprehension and object knowledge • Spared motor speech • Absence of outspoken agrammatism	• Impaired confrontation naming • Impaired single-word comprehension Additionally, at least three of the following features must be present: • Impaired object knowledge, particularly for low-frequency items • Surface dyslexia or dysgraphia • Spared repetition • Spared speech production	• Agrammatism in language production • Effortful, halting speech (e.g., apraxia of speech) Additionally, at least two of the following features must be present: • Impaired comprehension of syntactically complex sentences • Spared single-word comprehension • Spared object knowledge
Neuroimaging*	• Atrophy is most prominent in the left posterior perisylvian or parietal region on MRI • Hypoperfusion or hypometabolism is most prominent in the left posterior perisylvian or parietal region on SPECT or PET	• Atrophy is most prominent in the anterior temporal lobe on MRI • Hypoperfusion or hypometabolism is most prominent in the anterior temporal region on SPECT or PET	Atrophy is most prominent in the left posterior fronto-insular region on MRI Hypoperfusion or hypometabolism in the left posterior fronto-insular region on SPECT or PET
Most commonly associated pathology	• AD (50-60%)(Mesulam et al., 2008)	• FTLD-TDP (69-83%)(Gorno-Tempini et al., 2011)	• FTLD-tau (52%)(Mesulam et al., 2008)

PPA, primary progressive aphasia; LvPPA, logopenic/phonological variant PPA; SvPPA, semantic variant PPA; NFvPPA, nonfluent/agrammatic variant PPA; AD, Alzheimer's disease; FTLD-TDP-43, frontotemporal lobar dementia with ubiquitin and transactive response DNA binding protein kDa (TDP-43) pathology; FTLD-tau, frontotemporal lobar dementia with tau-positive pathology.

^*Disease epicenters. Damage can progress and become more widespread, including white matter (Acosta-Cabronero et al., 2011; Galantucci et al., 2011; Agosta et al., 2012; Mahoney et al., 2013) and functional connectivity (Guo et al., 2013; Agosta et al., 2014; Whitwell et al., 2015; Bonakdarpour et al., 2019) alterations.