[Language deficits in major forms of dementia and primary progressive aphasias: an update according to new diagnostic criteria].

In this review, we report current data on spoken and written language disorders in the most frequent dementia syndromes, namely Alzheimer' disease, vascular cognitive impairment and dementia with Lewy bodies. Language deficits are also the core features of three variants of primary progressive aphasia, namely the nonfluent/agrammatic, semantic and logopenic variants. This review reveals that, like other cognitive functions, language is highly vulnerable to neurodegenerative diseases. For some, language deficits result from impairment in linguistic processes per se, while for others, they are the direct consequence of impairments affecting working memory and executive functions. Language deficits in Alzheimer's disease and in nonfluent/agrammatic and semantic variants of primary progressive aphasia are well documented. By contrast, those about vascular cognitive impairment and dementia with Lewy bodies remain scarce and limited to large cognitive domains. The identification of logopenic variant of primary progressive aphasia is very recent, and more research is needed to complete the clinical description and identification of the functional origin of the disorders. Finally, knowledge on the impairment of written language in neurodegenerative diseases is less well documented than those on spoken language deficits. Other studies are therefore needed to improve the description of linguistic profiles and to provide additional elements to help in the differential diagnosis.