Reported symptoms and patterns of language impairment in bilingual speakers with primary progressive aphasia: a retrospective study

Background The relative scarcity of studies of bilingual speakers with primary progressive aphasia (PPA) leads to knowledge gaps regarding their symptoms and patterns of language impairment. It is unknown if PPA symptoms in bilingual speakers differ from those of monolingual speakers. In addition, it remains unclear if one of a bilingual speaker’s languages is more vulnerable to the onset of symptoms and/or is better preserved. Furthermore, bilingualism factors (e.g. order/age of language acquisition (L1/L2) and language dominance) may explain patterns of impairment both within and across the variants of PPA.Aims To characterize the bilingualism factors, speech and language symptoms, and patterns of language impairment in a retrospective cohort of bilingual speakers with PPA.Methods In a large cohort (N = 69) of bilingual speakers, we performed a chart review to extract information regarding self/caregiver-reported PPA symptoms, first language impacted by PPA at symptom onset, less preserved language at time of evaluation, and bilingual history factors (age/order of acquisition (L1/L2) and language dominance). We explored how emergence and presentation of symptoms associated with bilingualism factors.Results The presenting symptoms were mostly consistent with current PPA diagnostic criteria, although symptoms unique to bilingual speakers were reported. The language reported to first be impacted by PPA, as well as the less preserved language at the time of evaluation, was generally reported to be the less dominant language, regardless of PPA variant. These measures did not associate as closely with age/order of acquisition (L1 versus L2).Conclusion Bilingual speakers with PPA may report additional symptoms that reflect their ability to speak more than one language. The less dominant language was most susceptible to the initial impact of PPA and also tended to the less preserved language at the time of evaluation. Future studies of bilingual speakers with neurodegenerative diseases should systematically consider bilingualism factors, which are likely to contribute to clinical presentation and disease progression.