Brain Perfusion, Atrophy, and Dopaminergic Changes in Amyloid Negative Logopenic Primary Progressive Aphasia

Although most cases of logopenic variant primary progressive aphasia (lvPPA) are caused by Alzheimer's disease (AD), Lewy body disease (LBD) has also been reported. We assessed brain perfusion, atrophy, dopamine transporter (DAT) uptake, and language function among patients with lvPPA based on beta-amyloid. Thirty-three patients with lvPPA and 28 healthy controls (HCs) underwent MRI, ¹⁸F-florbetaben PET, and early- and late-phase DAT PET. All patients completed a language test. General linear models were applied to investigate the association of brain imaging with the aphasia quotient (AQ) and repetition scores. 20 (60.6%) and 13 (39.4%) of the lvPPA patients were amyloid-positive (lvPPA^A+) and -negative (lvPPA^A-), respectively. Language function was comparable between groups. Compared to HCs, the lvPPA^A+ had lower perfusion across widespread brain regions, the lvPPA^A- had lower perfusion in the left supramarginal and angular gyri, and both groups had lower DAT in the left caudate and bilateral substantia nigra. In the lvPPA^A-, AQ and repetition scores were positively correlated with perfusion in the left temporal and inferior parietal cortices, with perfusion in the left supramarginal gyrus mediating the effect of left substantia nigra DAT. Although AD is the most common underlying pathology of lvPPA, LBD may contribute to the logopenic phenotype.