Hippocampal fimbria atrophy and its mediating effect between cerebral small vessel disease and cognitive impairment

We aimed to investigate the relationship between the volume reduction in hippocampal (HP) subregions and cognitive impairment in patients with cerebral small vessel disease (CSVD). Clinical, cognitive, and magnetic resonance imaging data were obtained for 315 participants. The CSVD group included 146 participants with a total CSVD score of 1-4. 169 participants with a total CSVD score of zero were used as control group (CSVD-0). The volume differences of 19 HP subregions between CSVD and CSVD-0 groups were analyzed, and we investigated the hazard factors that might cause subregional volume reduction in HP. Mediation analysis was performed to detect the relationship among HP subregional volumes, CSVD burden, and cognitive function. In our results, significant differences can be found in the volumes of CA4 body, presubiculum-head, presubiculum-body, subiculum-body, GC-ML-DG-head, GC-ML-DG-body, fimbria, and HP tail between CSVD group and control group. Regression analysis showed that fimbria was the most impacted HP subregion by CSVD. And mediation analysis revealed fimbria volume was a mediator variable between total CSVD score and MoCA/SCWT score. These results suggest that the volumes of HP subregions, especially the fimbria, may be effective potential biomarkers for early detecting cognitive impairment in CSVD.