Beyond language: A structured profile of number processing impairment in logopenic primary progressive aphasia

BackgroundThe logopenic variant of primary progressive aphasia (lvPPA) is a language-led neurodegenerative syndrome commonly associated with Alzheimer's disease pathology and temporo-parietal degeneration. Although acalculia has been reported in lvPPA, numerical cognition has not been systematically investigated, and the specific profile of impairment remains poorly defined.ObjectiveTo characterize numerical cognition impairment in lvPPA using a comprehensive, theory-driven assessment battery and to examine its clinical relevance for diagnosis and cognitive characterization.MethodsFourteen individuals with lvPPA and twenty-eight demographically matched healthy controls completed the dCALQ, a standardized battery assessing number recognition and comprehension, number production (transcoding), and calculation. Participants also underwent global cognitive screening (Montreal Cognitive Assessment), language assessment (Detection Test for Language Impairments in Adults and the Aged), and measures of working memory and executive functioning. Group comparisons, intra-group domain analyses, correlation analyses, and receiver operating characteristic (ROC) analyses were performed.ResultsIndividuals with lvPPA showed significant impairments across all numerical domains compared with controls, with the most severe deficits in calculation, followed by transcoding, and milder impairment in number recognition and comprehension. Within the lvPPA group, performance differed significantly across domains, revealing a graded pattern of impairment. ROC analyses demonstrated excellent diagnostic accuracy for the dCALQ total score and strong discrimination for the calculation and transcoding domains.ConclusionsNumerical impairment is a robust and systematic feature of lvPPA rather than an incidental finding. The distinct numerical profile identified highlights the contribution of parietal-based cognitive dysfunction and supports the clinical utility of structured numerical assessment for cognitive characterization and diagnosis in dementia syndromes.