Primary progressive aphasia.

Primary progressive aphasia (PPA) is a progressive loss of specific language functions with relative sparing of other cognitive domains at least for the first few years of the illness. Based on the constellation of symptoms, PPA has been recently classified into a nonfluent, semantic, or logopenic variant. Nonfluent variant PPA is characterized by dysfluent and effortful speech, often combined with agrammatism. Also, some patients have initially predominant apraxia of speech. The neuroimaging findings in nfvPPA are in most cases progressive atrophy within the left inferior, opercular, and insular regions. Pathology is a tauopathy (FTLD-T), most often Pick's disease or CBD. Semantic variant PPA, on the other hand is characterized by fluent, but circumlocutory speech, then severe anomia and word-finding difficulties, all being associated with a progressive loss of lexical-semantic knowledge. As the disease progresses, the semantic impairment typically becomes multimodal. The clinical picture of svPPA is often associated with atrophy of the anterior regions of the temporal lobes, usually more prominent on the left side. The majority of these patients have TDP-43 pathology. The third, most recently described form of PPA is the logopenic variant characterized by decreased spontaneous speech output with frequent word-finding pauses, phonologic parahpasias, and repetition deficits. It resembles aphasia in Alzheimer's disease. Imaging abnormalities in lvPPA have been predominantly found in the left temporo-parietal junction area, and the pathological changes have been often those of AD.