Altered neurovascular coupling in semantic variant primary progressive aphasia

Semantic variant primary progressive aphasia (svPPA) is one of the main clinical phenotypes of frontotemporal lobar degeneration. Changes in both neuronal activity and cerebral perfusion have been observed in svPPA, suggesting a possible breakdown of neurovascular coupling (NVC).

To investigate alterations in NVC and their correlations with clinical manifestations in svPPA patients.

In this study, a cohort consisting of 19 subjects diagnosed with svPPA and 36 cognitively unimpaired controls (CUCs) have been enrolled for analysis. All participants underwent multimodal magnetic resonance imaging (MRI) scans, resting-state functional MRI and arterial spin labelling, and neuropsychological assessments. The amplitude of low-frequency fluctuations (ALFF) and cerebral blood flow (CBF) were obtained to measure neural activity and perfusion, respectively. The calculation of voxel CBF-ALFF correlation and CBF/ALFF ratio enables the assessment of global NVC and regional NVC, respectively. Correlations between the CBF/ALFF ratios and cognitive scores of the svPPA patients were analyzed. The relationships between the CBF/ALFF ratios and the cognitive performance of the svPPA patients were investigated through correlational analyses.

Compared with CUCs, svPPA patients had decreased global CBF-ALFF correlation coefficients (p < 0.001) and lower CBF/ALFF ratios in bilateral inferior temporal gyrus, fusiform gyrus, left temporal pole and middle temporal gyrus (p < 0.05). In svPPA patients, the CBF/ALFF ratios in the left inferior and middle temporal gyrus correlated positively with naming ability and general cognition, respectively.

The study indicate that NVC is disrupted in svPPA patients and is relevant to cognitive and language function.