Hippocampal subfield volumetry in patients with subcortical vascular mild cognitive impairment

Xinwei Li, Deyu Li, Qiongling Li, Yuxia Li, Kuncheng Li, Shuyu Li, Ying Han
2016 Scientific Reports  
Memory impairment is a typical characteristic of patients with subcortical vascular mild cognitive impairment (svMCI) or with amnestic mild cognitive impairment (aMCI). The hippocampus, which plays an important role in the consolidation of information from short-term memory to long-term memory, is a heterogeneous structure that consists of several anatomically and functionally distinct subfields. However, whether distinct hippocampal subfields are differentially and selectively affected by
more » ... pathology and whether these abnormal changes in hippocampal subfields are different between svMCI and aMCI patients are largely unknown. A total of 26 svMCI patients, 26 aMCI patients and 26 healthy controls matched according to age, gender and years of education were enrolled in this study. We utilized an automated hippocampal subfield segmentation method provided by FreeSurfer to estimate the volume of several hippocampal subfields, including the cornu ammonis (CA) areas, the dentate gyrus (DG), the subiculum and the presubiculum. Compared with controls, the left subiculum and presubiculum and the right CA4/DG displayed significant atrophy in patients with svMCI. Interestingly, we also found significant differences in the volume of the right CA1 between the svMCI and aMCI groups. Taken together, our results reveal region-specific vulnerability of hippocampal subfields to svMCI pathology and identify distinct hippocampal subfield atrophy patterns between svMCI and aMCI patients. Vascular dementia (VaD) and Alzheimer's disease (AD) are regarded as the most common forms of dementia in the elderly. Subcortical VaD (SVaD) is a small vessel disease 1 , which constitutes approximately half of all cases of VaD 2 . SVaD is characterized by multiple lacunar infarcts and ischemic white matter hyperintensity (WMH) 3 . Similar to amnestic mild cognitive impairment (aMCI), which is thought to represent a transitional state between normal aging and AD, subcortical vascular mild cognitive impairment (svMCI) refers to a prodromal stage of SVaD 4 . The early diagnosis of svMCI may be clinically important because it is potentially reversible by modifying the vascular risk factors 5,6 . Memory deficit is an important characteristic of AD and is also observed in subcortical vascular disease, although to a lesser extent compared with AD 7,8 . The hippocampus plays an important role in memory processing. Hippocampal atrophy has been found in patients with aMCI/AD and is widely considered a neuroimaging hallmark for the early diagnosis of AD 9 . A reduced size of the hippocampus has also been reported in svMCI and SVaD patients 10-13 . Moreover, the extent of hippocampal atrophy has shown a strong association with cognitive decline in subcortical ischemic vascular disease 14, 15 . Notably, the hippocampus is not a homogeneous structure but rather is composed of several subfields, specifically the cornu ammonis (CA) areas 1-4, the dentate gyrus (DG), the subiculum and the presubiculum 16 . These subfields have distinct histological characteristics and appear to be differentially affected by various neurodegenerative diseases 17 . An autopsy study found substantial neuronal loss in the CA1 and the subiculum in VaD patients with microvascular pathology 18 . Recently, studies employing a three-dimensional surface mapping technique have reported deformations of hippocampal shape in the lateral body (CA1) among svMCI patients, and
doi:10.1038/srep20873 pmid:26876151 pmcid:PMC4753487 fatcat:q3uydqtwfzdrvas3sygcsvvig4