Primary Progressive Aphasias in Bilinguals and Multilinguals

Primary progressive aphasia (PPA) is the result of neurodegeneration affecting language abilities that continue to decline as the disease progresses. There are three main variants of PPA: non‐fluent, semantic, and logopenic. Deficits may occur in different areas of language, such as lexical retrieval, auditory comprehension, syntactic structure, processing morphological components, and repetition abilities. However, the impact on language is not comparable across all individuals with PPA; rather it differs for each of the different variants based on the underlying pattern of neural change. In bilinguals or multilinguals with PPA, the language decline has an added layer of complexity. Decline may occur across the different languages in parallel, or differentially, and a number of factors may affect the pattern of decline. Recognizing the factors that most affect language decline in bilinguals and multilinguals with PPA, along with identifying the neural changes occurring in the brain, can increase our understanding of language organization in the bilingual or multilingual brain. It should be noted that language decline is not the only decline associated with PPA, as changes in cognition and behaviour have also been observed, particularly in the later stages (e.g. Rosen et al. 2006). However, language is the most salient decline in PPA so we focus on language in this chapter