Subcortical Vascular Cognitive Impairment-A Longitudinal Perfusion Imaging Study

描述（申请人提供）：老年人小血管缺血性疾病，其磁共振成像（MRI）的特征是T2和FLAIR序列上的白质高信号（WMH），推测是由慢性灌注不足引起的。WMH变化几乎无处不在，对非痴呆个体的认知和运动加工产生负面影响，对阿尔茨海默病病理有协同作用，并增加功能下降和痴呆的风险。由小血管脑血管疾病引起的认知能力下降被称为皮层下血管性认知障碍（VCI），这可能是老年人轻度认知障碍的一个未被充分认识的原因。尽管最近我们对WMH变化对老年人认知和运动健康的影响的理解取得了进展，但这些变化的潜在机制和功能轨迹，以及随之而来的皮质下VCI和痴呆的风险在很大程度上仍然未知。本研究的目的是研究脑血流量随时间变化对WMH负荷积累的影响，确定WMH病变是否是弥漫性病理过程的局灶性征象，并确定导致认知和运动障碍风险增加的解剖和灌注MRI标志物。具体目的是：1)确定灌注改变在老年人WMH积累形成中的作用；2)表征WMH和灌注相关的正常白质（NAWM）和胼胝体白质微结构变化；3)确定认知和运动衰退的MRI生物标志物。65岁以上的非痴呆老年人将被邀请参加。除了每年常规的心理测量和神经学测试外，还将对受试者进行纵向随访，对其在家步态和运动活动进行不显眼的评估。80名受试者将接受每年一次的高场（3和7特斯拉）MRI。通过动脉自旋标记（一种量化脑血流的非侵入性方法）获得灰质和白质灌注的纵向测量。在NAWM和胼胝体中，将使用扩散张量成像和定量T1松弛成像来评估白质完整性微结构下降的证据。所有受试者将获得WMH病变负荷的体积定量。本研究建议使用高视场先进成像技术来研究老年人群中wmh相关认知障碍和运动功能下降的机制。本研究将首次前瞻性研究脑灌注不足对认知障碍和痴呆风险老年人认知和运动功能的影响，并建立CBF与常见wmh变化之间的因果关系。此外，本研究将确定WMH病变对NAWM和胼胝体的广泛微结构损伤的程度和功能影响。最终，本提案的目标是确定VCI背后的机制，并识别有认知和运动障碍风险的老年人，以便制定早期治疗和预防措施。

DESCRIPTION (provided by applicant): Small vessel ischemic disease in the elderly whose signature on Magnetic Resonance Imaging (MRI) is white matter hyperintensities (WMH) on T2 and FLAIR sequences is presumed to be caused by chronic hypoperfusion. WMH change is nearly ubiquitous, negatively impacts cognitive and motor processing in nondemented individuals, has synergistic effects on Alzheimer disease pathology, and increases the risk of functional decline and dementia. Cognitive decline that occurs as a result of small vessel cerebrovascular disease has been termed subcortical vascular cognitive impairment (VCI), a likely underrecognized cause of mild cognitive impairment in the elderly. Despite recent advances in our understanding of the impact of WMH changes on cognitive and motor health in the elderly, the underlying mechanisms and functional trajectory of these changes, as well as the attendant risks of subcortical VCI and dementia remain largely unknown. The goals of this study are to investigate the effects of changes in cerebral blood flow over time on WMH burden accumulation, determine whether WMH lesions are focal signs of a more diffuse pathological process, and identify anatomical and perfusion MRI markers that confer increased risk of cognitive and motor impairment. Specific aims are to: 1) Identify the role of altered perfusion in the formation of WMH accumulation in the elderly, 2) Characterize WMH and perfusion-related microstructural white matter changes in normal appearing white matter (NAWM) and the corpus callosum, and 3) Determine MRI biomarkers of cognitive and motor decline. Non-demented seniors over age 65 will be asked to participate. In addition to annual conventional psychometric and neurologic testing, subjects will also be followed longitudinally with unobtrusive assessment of in-home gait and motor activity. Eighty subjects will undergo yearly high-field (3 and 7 Tesla) MRI. Longitudinal measures of grey and white matter perfusion will be obtained using arterial spin labeling, a non-invasive means of quantifying cerebral blood flow. Evidence of microstructural decline in white matter integrity will be evaluated in NAWM and the corpus callosum using diffusion tensor imaging and quantitative T1 relaxography. Volumetric quantification of WMH lesion burden will be obtained for all subjects. This study proposes to use high-field advanced imaging techniques to investigate the mechanisms behind WMH-related cognitive impairment and motor function decline in a well-characterized elderly cohort. This study would be one of the first to prospectively study the effects of cerebral hypoperfusion over time on cognitive and motor function in elderly at risk for cognitive impairment and dementia, and establish a causal relationship between CBF and commonly observed WMHs changes. In addition, this study will determine the extent and functional effects of widespread microstructual damage to the NAWM and corpus callosum in those with WMH lesions. Ultimately, the goal of this proposal is to determine the mechanisms behind VCI and identify elderly at risk for cognitive and motor impairment, so that early treatment and preventative measures can be instituted.