Cerebral Small Vessel Disease Influences Hippocampal Subfield Atrophy in Mild Cognitive Impairment

To investigate patterns of hippocampal subfield atrophy among patients with amnestic mild cognitive impairment, stratified by severity of small vessel disease (SVD) and corresponding associations with cognitive domains. One hundred seventy-six MCI subjects (mean age = 65.56 years, SD = 8.77) underwent neuropsychological assessments and magnetic resonance imaging. SVD was rated 0 (no SVD), 1 (mild SVD) and 2 (moderate to severe SVD) based on load of white matter hyperintensities (WMH) and lacunes. Demographics, cerebrovascular risk factors, grey and white matter volumes and hippocampal subfield atrophies were compared across SVD severity through ANCOVA analyses. Subjects were categorized into positive or negative SVD-hippocampal subfield atrophy (HSA) and influence of positive SVD-HSA on episodic memory and frontal executive function was evaluated through ANCOVA analyses. All analyses corrected for covariates and bias-corrected bootstrap estimation with 1000 resamples was applied with Bonferroni correction. Hippocampal subfield atrophy worsened with increasing SVD severity. Positive SVD-HSA was characterised by significant atrophy in the subiculum, CA1, CA4, molecular layer and dentate gyrus. Greater atrophy was seen with moderate to severe SVD compared to mild SVD in these subfields. Atrophy in the five subfields of SVD-HSA was significantly associated with poor episodic memory and frontal executive function. Presence and burden of SVD influences the pattern and severity of hippocampal subfield atrophy. SVD-related hippocampal subfield atrophy is associated with poorer episodic memory and frontal executive function in mild cognitive impairment.