Primary progressive aphasia in Italian and English: a cross-linguistic cohort study

Abstract

ABSTRACTBackground and objectivesPrimary progressive aphasia (PPA) signifies a diverse group of neurodegenerative disorders principally affecting language functions. The major syndromic variants of PPA present with distinct profiles of linguistic deficits. However, current concepts and diagnosis of PPA are largely based on English-speaking patients, while few studies have explored how PPA syndromes might vary between languages. Here we undertook a comprehensive neuropsychological comparison of all major PPA syndromes in two languages with contrasting characteristics: Italian and English.MethodsWe retrospectively compared the PPA cohorts attending our specialist referral centres on neuropsychological tests sampling a range of linguistic and general cognitive domains. The cohorts comprised 106 native Italian-speakers with PPA (14 nonfluent/agrammatic variant [nfvPPA], 20 semantic variant [svPPA], 41 logopenic variant [lvPPA], 31 mixed PPA [mPPA]) and 166 native English-speakers with PPA (70 nfvPPA, 45 svPPA, 42 lvPPA, 9 mPPA). Neuropsychological scores were normalised to healthy older native speakers (adjusted for age and years of education) and dichotomised (impaired/unimpaired) to identify the proportion of each cohort showing impairment on each test. Cohorts were compared in logistic regression models, covarying for symptom duration and overall cognitive severity.ResultsThe English PPA cohort was significantly younger (mean 62.7 years) than the Italian cohort (mean 65.9 years; p=0.003), with longer symptom duration (mean 4.6 vs 3.1 years; p=0.048), a higher proportion of nfvPPA cases (42% vs. 13%, p<0.001) and lower proportions of lvPPA (25% vs. 38%, p=0.019) and mPPA (5% vs. 29%, p<0.001). Compared with Italian-speaking patients, English-speaking nfvPPA patients had less frequent expressive agrammatism (p=0.015) and more frequently impaired single-word comprehension (p=0.013) and nonverbal working memory (p=0.041). English svPPA patients had more frequent surface dyslexia (p=0.046) and dysgraphia (p=0.021), while English lvPPA patients had more frequently impaired single-word comprehension (p<0.001), word repetition (p=0.02), nonverbal working memory (p=0.005) and visuospatial perception (p<0.001).DiscussionLanguage-specific characteristics importantly influence PPA phenotypes: degeneration of language networks may predispose to expressive agrammatism in Italian (reflecting its morphological complexity) and to impaired spoken word processing and regularisation errors in English (reflecting its articulatory, acoustic and orthographic complexity). These findings have implications for diagnosis, management and cross-linguistic collaborative initiatives in PPA.