Sentence Production in Bilingual and Multilingual Aphasia: A Scoping Review

Language processing impairments across different dimensions result in deficits of informational content, syntactic complexity, and morphological well-formedness of sentences produced by people with aphasia (PWA). Deficits in language processing affect linguistic skills of bi/multilingual PWA in all languages that they have acquired prior to aphasia. However, the impairments of dual or multiple languages in aphasia may not necessarily be parallel. One language may be more preserved than another and be recovered at different paces, including sentence production abilities. This scoping review aims to compare syntactic characteristics and errors demonstrated by bi/multilingual PWAs between their acquired languages and to explore the nature of bilingual impairments in primary progressive aphasia (PPA). We conducted an online search on three databases (MEDLINE, SciVerse Scopus, and Taylor and Francis publications) for original studies on sentence production of bi/multilingual aphasia that were published between 1991 and 2021 using keywords related to “bilingualism”, “aphasia”, and “speech production”. Based on the titles, abstracts, and full-text screenings, 13 studies were found to have met our inclusion criteria. A qualitative synthesis of the accumulated evidence was conducted following the PRISMA guidelines. Collectively, past researchers reported dominance in L1 with higher occurrences of linguistic errors in L2 among participants with sudden onset aphasia. In PPA, language impairments were found to be comparable between L1 and L2, which may indicate parallel deterioration. It is noted that this review is not exhaustive and many of the reviewed studies were based on single case studies. This review also highlighted an urgent need for investigation into multilingual PPA to fully comprehend the nature of sentence production impairment.