Reading prosody in the non-fluent and logopenic variants of primary progressive aphasia

Primary progressive aphasia (PPA) is a clinical syndrome including a group of neurodegenerative disorders that present with language impairment. We hypothesised that impairment in reading prosody may be present in a subgroup of patients with PPA, and particularly non-fluent PPA (nfvPPA), because of the impairment of key brain regions involved in the pathophysiology of speech dysprosody and reading observed in these patients.

Ninety-five participants were evaluated using a narrative text comprising several declarative, exclamatory, and interrogative sentences, as well as a comprehensive language protocol. Patients were also examined with ¹⁸F-fluorodeoxyglucose positron emission tomography imaging.

Impairment was more frequent and more severe in patients with nfvPPA, especially in the subgroup of patients with Apraxia of Speech (AOS). Patients with nfvPPA, mainly those with AOS, showed lower values in several pitch variables. Statistically significant differences were also observed in sentence duration, reading times, and types of error. A regression model including mean length of utterances, time after full stops, number of pauses, and number of pitch variables below the mean, correctly classified 70-71.3% of patients. When combined with sentence repetition task, the percentage of patients correctly classified was 96.2% and 92.4%, respectively, for each classification. The left frontal lobe was the region most strongly correlated with reading prosody parameters. Specific tasks displayed additional correlations with the left parietal and occipital lobes; right frontal lobe, thalamus, and caudate; and right cerebellum.

Reading prosody is relevant in PPA diagnosis and classification. Because reading prosody may be quantified, it is amenable to use in diagnosis and follow-up. We found neuroimaging correlation with metabolism in the left frontal lobe, as well as in other regions including the right frontal lobe, basal ganglia, and cerebellum, which suggests that these may be the main brain regions involved in prosodic control in patients with PPA.