EXPRESS: Stage-Dependent Deep Gray Matter Alterations in Cerebral Small Vessel Disease Revealed by 7T Quantitative Susceptibility Mapping

Susceptibility alterations in deep gray matter (DGM) across clinical stages of cerebral small vessel disease (CSVD) remain unclear. In this case-control study, we used 7-tesla magnetic resonance imaging quantitative susceptibility mapping (QSM) with source separation (APART-QSM) to characterize stage-related changes in normal controls, preclinical CSVD, and symptomatic CSVD. Compared with controls, CSVD showed increased QSM in the basal ganglia, particularly the putamen and globus pallidus, whereas small-magnitude QSM reductions were observed in selected thalamic and amygdalar subregions (all P < 0.05). Source separation revealed that basal ganglia abnormalities were mainly associated with increased paramagnetic components, whereas some thalamic alterations may involve increased diamagnetic components, suggesting distinct susceptibility contributions. Lower MoCA scores were associated with higher QSM and paramagnetic values in the globus pallidus, as well as higher diamagnetic values across the thalamus, putamen, and nucleus accumbens (all P < 0.05). Notably, right anterior globus pallidus QSM discriminated symptomatic CSVD from controls with the highest accuracy (AUC = 0.818). These findings reveal DGM susceptibility patterns associated with cognitive impairment, suggesting that 7T QSM and susceptibility source separation may provide complementary information for early CSVD characterization and future longitudinal evaluation.