脑膜瘤患者伽玛刀治疗后脑白质损伤与认知功能的关系

目的探讨脑膜瘤患者伽玛刀治疗后脑白质损伤与患者认知功能的关系。方法 89例接受伽玛刀治疗的脑膜瘤患者在伽玛刀治疗前及治疗后1月、6月,分别进行磁共振检查(FLAIR序列),采用脑白质高信号Schelten评分评估脑白质损伤严重程度;同时以蒙特利尔认知评估量表(MoCA)评定患者认知功能。结果①治疗后1月、6月患者Schelten评分均较治疗前显著增高,差异均有统计学意义(t=4.066,5.376;P=0.000);②治疗后1月、6月患者MoCA评分均较治疗前显著下降,差异均有统计学意义(t=2.370,2.265;P=0.019,0.024);③治疗后1月、6月时患者的Schelten评分与MoCA评分之间有负性相关(r=-0.308,-0.402;P=0.038,0.007)。结论伽玛刀治疗可致脑膜瘤患者脑白质损伤,并与其认知功能的降低有关。     

Do Deductive and Probabilistic Reasoning Abilities Decline in Older Adults?

This present study investigated whether older adults' ability to accurately discriminate between deductive and probabilistic reasoning tasks declines with age, and whether this ability correlates with cognitive ability as measured by the Montreal Cognitive Assessment (MoCA) test. Seventy‐eight adults (65–92 years) were tested for their abilities to carry out deductive and probabilistic reasoning. Pearson correlations were conducted to determine the relationships among age, MoCA, deductive reasoning, probabilistic reasoning, and overall discrimination ability. Separate single‐factor analyses of variance were used to determine differences across age groups (65–74, 75–84, 85–94) on the MoCA, deductive and probabilistic reasoning, and overall discrimination ability. Ability to discriminate between the two tasks did not decline with age, nor did they correlate with scores of cognitive ability as measured by the MoCA. Furthermore, those with MoCA scores showing mild cognitive impairment appeared to retain all of these abilities. This leads to the conclusion that reasoning abilities may be retained while general cognitive skills decline. This in turn supports the notion that reasoning, both deductive and probabilistic, may be more domain specific than they are often considered to be.     

Taking the pulse of aging: Mapping pulse pressure and elasticity in cerebral arteries with optical methods

Cerebrovascular support is crucial for healthy cognitive and brain aging. Arterial stiffening is a cause of reduced brain blood flow, a predictor of cognitive decline, and a risk factor for cerebrovascular accidents and Alzheimer's disease. Arterial health is influenced by lifestyle factors, such as cardiorespiratory fitness (CRF). We investigated new noninvasive optical measures of cerebrovascular health, which provide estimates of arterial pulse parameters (pulse pressure, transit time, and compliance/elasticity) within specific cerebral arteries and cortical regions, and low‐resolution maps of large superficial cerebral arteries. We studied naturally occurring variability in these parameters in adults (aged 55–87), and found that these indices of cerebrovascular health are negatively correlated with age and positively with CRF and gray and white matter volumes. Further, regional pulse transit time predicts specific neuropsychological performance.     

Arterial stiffness,the brain and cognition: A systematic review

BackgroundArterial stiffness is a known predictor of cardiovascular disease, and has also been associated with markers of cerebral small vessel disease as well as poor cognitive function and cognitive decline. The consistency of these associations and their relationship to each other are unclear.MethodWe conducted a systematic review of the evidence associating arterial stiffness with cognitive function and cognitive decline, and with makers of cerebral small vessel disease, specifically lacunar infarcts and white matter hyperintensities.ResultsThirteen cross-sectional studies examining arterial stiffness and white matter hyperintensities or lacunar infarctions reported a positive association between increased arterial stiffness and radiological findings of cerebral small vessel disease. Two longitudinal studies examining the relationship between arterial stiffness and white matter hyperintensities found increased pulse wave velocity to be an independent predictor of white matter hyperintensity volume. Fifteen cross-sectional and seven longitudinal studies examining arterial stiffness and cognition were identified. Fourteen of the fifteen cross-sectional studies associated increased arterial stiffness with lower cognitive function, and six of the seven longitudinal studies found arterial stiffness to be predictive of cognitive decline.ConclusionArterial stiffness is associated with cerebral small vessel disease and decreased cognitive function. However methodological limitations such as differing covariates between studies and an over-reliance on the MMSE to measure cognition are a concern across much of the literature.     

Effects of sustained cognitive activity on white matter microstructure and cognitive outcomes in healthy middle-aged adults: A systematic review

Adults who remain cognitively active may be protected from age-associated changes in white matter (WM) and cognitive decline. To determine if cognitive activity is a precursor for WM plasticity, the available literature was systematically searched for Region of Interest (ROI) and whole-brain studies assessing the efficacy of cognitive training (CT) on WM microstructure using Diffusion Tensor Imaging (DTI) in healthy adults (> 40 years). Seven studies were identified and included in this review. Results suggest there are beneficial effects to WM microstructure after CT in frontal and medial brain regions, with some studies showing improved performance in cognitive outcomes. Benefits of CT were shown to be protective against age-related WM microstructure decline by either maintaining or improving WM after training. These results have implications for determining the capacity for training-dependent WM plasticity in older adults and whether CT can be utilised to prevent age-associated cognitive decline. Additional studies with standardised training and imaging protocols are needed to confirm these outcomes.     

Rest-activity rhythms and white matter microstructure across the lifespan

Study ObjectivesThe purpose of this study was to examine how rest-activity (RA) rhythm stability may be associated with white matter microstructure across the lifespan in healthy adults free of significant cardiovascular risk.MethodsWe analyzed multi-shell diffusion tensor images from 103 healthy young and older adults using tract-based spatial statistics (TBSS) to examine relationships between white matter microstructure and RA rhythm stability. RA measures were computed using both cosinor and non-parametric methods derived from 7 days of actigraphy data. Fractional anisotropy (FA) and mean diffusivity (MD) were examined in this analysis. Because prior studies have suggested that the corpus callosum (CC) is sensitive to sleep physiology and RA rhythms, we also conducted a focused region of interest analysis on the CC.ResultsGreater rest-activity rhythm stability was associated with greater FA across both young and older adults, primarily in the CC and anterior corona radiata. This effect was not moderated by age group. While RA measures were associated with sleep metrics, RA rhythm measures uniquely accounted for the variance in white matter integrity.ConclusionsThis study strengthens existing evidence for a relationship between brain white matter structure and RA rhythm stability in the absence of health risk factors. While there are differences in RA stability between age groups, the relationship with brain white matter was present across both young and older adults. RA rhythms may be a useful biomarker of brain health across both periods of adult development.     

Risk factors for cerebral hypoperfusion, mild cognitive impairment, and dementia

Putative risk factors accelerating mild cognitive decline and dementia were correlated with repeated measures of cerebral atrophy, CT, densitometry, perfusions, and cognitive testing among neurologically and cognitively normative aging volunteers. A total of 224 normative subjects at increased risk for cognitive decline were admitted to the study. Mean entry age was 59.5 +/- 15.8 years. Mean follow-up is 5.8 +/- 3.3 years. At follow-up, 22 developed mild cognitive impairment (41 CCSE >/= -3), 19 became demented-8 with Vascular type (VAD), 11 with Alzheimer's type (DAT)-and 183 remain cognitively unchanged. Cerebral atrophy, tissue densities, and perfusions were measured by Xe-CT. After age 60, cerebral atrophy, ventricular enlargement, and polio- and leuko-araiosis geometrically increased as perfusions declined. Risk factors accelerating perfusional decline, cerebral atrophy, polio-araiosis, and leuko-araiosis were: transient ischemic attacks (TIAs), hypertension, smoking, hyperlipidemia, and male gender. At age 71.5 +/- 11.9, mild cognitive impairment began accelerated by TIAs, hypertension and heart disease. Leuko-araiosis began before cognitive decline. TIAs, hypertension, and hyperlipidemia correlated with VAD. Excessive cortical perfusional decrease, gray and white matter hypodensities, and cerebral atrophy correlate with cognitive decline.     

Determinants of cerebellar and cerebral volume in the general elderly population

In a population-based study of 3962 community-dwelling nondemented elderly we investigated the relation of age, sex, cardiovascular risk factors, and the presence of infarcts with cerebellar volume, and its interrelationship with cerebral volumes. Cerebellar and cerebral gray and white matter were segmented using Freesurfer version 4.5 (http://surfer.nmr.mgh.harvard.edu/). We used linear regression analyses to model the relationship between age, sex, cardiovascular risk factors, brain infarcts, white matter lesions (WMLs) and cerebellar and cerebral volume. Smaller cerebellar volumes with increasing age were mainly driven by loss of white matter. Diabetes, higher serum glucose and lower cholesterol levels were related to smaller cerebellar volume. No association was found between hypertension, smoking, apolipoprotein E (ApoE) genotype, and cerebellar volume. Supratentorial lacunar infarcts and WMLs were related to smaller cerebellar volume. Infratentorial infarcts were related to smaller cerebellar white matter volume and total cerebral volume. This study suggests that determinants of cerebellar volume do not entirely overlap with those established for cerebral volume. Furthermore, presence of infarcts or WMLs in the cerebrum can affect cerebellar volume.     

合并微出血对脑小血管闭塞性卒中患者认知功能的影响及其与P300的关系

目的 探讨合并微出血（CMBs）对脑小动脉闭塞性卒中（SAO）患者认知功能的影响及与事件相关电位（ERP）P300的相关性。方法 选取本院2017年12月~2019年4月脑病科SAO患者70例作为研究对象,应用蒙特利尔认知评估量表（MoCA）进行认知功能评估。应用1.5T超导磁共振对所有患者进行常规序列及磁敏感（SWI）序列检查,分析SAO患者认知功能损伤与CMBs的关系。采用Keypoint诱发电位仪检测P300电位,分析SAO患者CMBs与P300电位关系。结果 本研究最终纳入70例SAO患者,其中MoCA总分异常者48例,MoCA总分正常者22 例。年龄、教育年限、高血压病史、白质疏松程度和CMBs的有无与SAO患者MoCA评分异常有关（P＜0.05）。Logistic回归分析发现,CMBs的有无（OR=5.648,95%CI=1.105~28.869,P=0.038）仍然是MoCA评分异常的独立危险因素。微出血（CMBs）组 MoCA总分降低,P300潜伏期显著延长、波幅明显降低,差异均有统计学意义（P＜0.05）。CMBs程度与P300潜伏期相关Pz（r=0.252,P＜0.05）;Cz（r=0.296,P＜0.05）。结论 CMBs与SAO患者认知功能损伤相关,伴CMBs的SAO患者P300电位有明显改变,P300可作为评估SAO合并CMBs患者的认知功能障碍的客观指标之一。     

Age-related decline in white matter tract integrity and cognitive performance: A DTI tractography and structural equation modeling study

Age-related decline in microstructural integrity of certain white matter tracts may explain cognitive decline associated with normal aging. Whole brain tractography and a clustering segmentation in 48 healthy individuals across the adult lifespan were used to examine: interhemispheric (corpus callosum), intrahemispheric association (cingulum, uncinate, arcuate, inferior longitudinal, inferior occipitofrontal), and projection (corticospinal) fibers. Principal components analysis reduced cognitive tests into 6 meaningful factors: (1) memory and executive function; (2) visuomotor dexterity; (3) motor speed; (4) attention and working memory; (5) set-shifting/flexibility; and (6) visuospatial construction. Using theory-based structural equation modeling, relationships among age, white matter tract integrity, and cognitive performance were investigated. Parsimonious model fit demonstrated relationships where decline in white matter integrity may explain age-related decline in cognitive performance: inferior longitudinal fasciculus (ILF) with visuomotor dexterity; the inferior occipitofrontal fasciculus with visuospatial construction; and posterior fibers (i.e., splenium) of the corpus callosum with memory and executive function. Our findings suggest that decline in the microstructural integrity of white matter fibers can account for cognitive decline in normal aging.     

Structural MRI covariance patterns associated with normal aging and neuropsychological functioning

Structural magnetic resonance imaging (MRI) studies have shown dramatic age-associated changes in grey and white matter volume, but typically use univariate analyses that do not explicitly test the interrelationship among brain regions. The current study used a multivariate approach to identify covariance patterns of grey and white matter tissue density to distinguish older from younger adults. A second aim was to examine whether the expression of the age-associated covariance topographies is related to performance on cognitive tests affected by normal aging. Eighty-four young (mean age=24.0) and 29 older (mean age=73.1) participants were scanned with a 1.5T MRI machine and assessed with a cognitive battery. Images were spatially normalized and segmented to produce grey and white matter density maps. A multivariate technique, based on the subprofile scaling model, was used to capture sources of between- and within-group variation to produce a linear combination of principal components that represented a "pattern" or "network" that best discriminated between the two age groups. Univariate analyses were also conducted with statistical parametric maps. Grey and white matter covariance patterns were identified that reliably discriminated between the groups with greater than 0.90 sensitivity and specificity. The identified patterns were similar for the univariate and multivariate techniques, and involved widespread regions of the cortex and subcortex. Age and the expression of both patterns were significantly associated with performance on tests of attention, language, memory, and executive functioning. The results suggest that identifiable networks of grey and white matter regions systematically decline with age and that pattern expression is linked to age-related cognitive decline.     

Structural correlates of cognitive domains in normal aging with diffusion tensor imaging

The involvement of brain structures in specific cognitive functions is not straightforward. In order to characterize the brain micro-structural correlates of cognitive domains, 52 healthy subjects, age 25–82 years, completed a computerized neuropsychological battery and were scanned using magnetic resonance diffusion tensor imaging. Factor analysis of 44 different cognitive scores was performed, isolating three cognitive domains—executive function, information processing speed and memory. Partial correlation was conducted between DTI parameters and each of the three cognitive domains controlling for age and motor function. Regions showing significant correlations with cognitive domains are domain-specific and are consistent with previous knowledge. While executive function was correlated with diffusion tensor imaging (DTI) parameters in frontal white matter and in the superior longitudinal fasciculus, information processing speed was correlated with DTI parameters in the cingulum, corona radiata, inferior longitudinal fasciculus, parietal white matter and in the thalamus. Memory performance was correlated with DTI measures in temporal and frontal gray matter and white matter regions, including the cingulate cortex and the parahippocampus. Thus, inter-subject variability in cognitive performance and tissue morphology, as expressed by diffusion tensor magnetic resonance imaging, can be used to relate tissue microstructure with cognitive performance and to provide information to corroborate other functional localization techniques.     

晚发型抑郁症患者脑白质胆碱能通路的磁共振研究

目的探讨晚发型抑郁症患者脑白质胆碱能通路的改变及其与认知功能障碍的关系。方法晚发型抑郁症患者(患者组,n=20)行磁共振检查,采用胆碱能通路高信号评分(CHIPS)评估患者脑白质胆碱能通路的改变、采用蒙特利尔认知评估量表(MoCA)评定认知功能,并与正常老年人(对照组,n=20)进行对照。结果①患者组CHIPS评分显著高于对照组、MoCA评分显著低于对照组,差异均有统计学意义(t=3.119,3.025;P=0.0032,0.0044);②患者组、对照组的CHIPS评分均与MoCA评分负相关(r=-0.490,-0.482;P=0.026,0.038)。结论晚发型抑郁症患者存在脑白质胆碱能通路受损,并与患者的认知功能改变有关。     

Vagal modulation and aging

Cardiovascular disease accounts for approximately 30% of all deaths worldwide, and will only worsen as the world's population ages. It is well-established that age, per se, is a major risk factor and contributor to all cardiovascular morbidities and mortalities. However, environmental factors, including a lack of exercise, appear to play a critical role in the onset and progression of cardiovascular disease. This paper reviews the literature on cardiac variability and aging and addresses risk factors associated with aging that can be modified and possibly attenuate the decline of heart rate variability with aging, including exercise training to increase vagal modulation. Thus, results of the studies described in this review support a potential benefit of increasing or maintaining fitness in order to slow the decline of parasympathetic control of HR with normal aging.     

糖尿病对脑白质病变伴轻度认知功能障碍患者认知功能的影响

目的 探讨糖尿病与脑白质病变(WML)伴轻度认知功能障碍(MCI)患者认知功能减退的关系。方法 2012年1—12月在大坪医院神经内科住院病人中选择257例WML伴MCI患者进行前瞻性研究,随访时间为1年。收集患者血管危险因素(VRFs)及颅脑MRI检查结果,同时行神经心理学测试了解认知功能状态;根据1年内简易精神状态检查量表(MMSE)减少值分为认知功能下降组(≥3分)及无认知功能下降组(≤2分),并比较两组各种危险因素的差异。结果 257例中有246例(95.7%)患者完成了1年的观察随访过程,11例删失者中8例死亡、3例退出观察。246例中,认知功能下降组154例(62.6%),无认知功能下降组92例(37.4%);其中36例在观察期间发生卒中,余210例患者纳入线性回归分析。除受教育水平及血脂异常外,年龄、性别、高血压、糖尿病、短暂性脑缺血发作等各危险因素两组比较差异均有统计学意义 (P值均＜0.05)。糖尿病、基线WML程度及随访期间WML程度的加重与1年内MMSE减少值呈显著的线性关系,且对认知功能减退的影响由大至小依次为基线WML程度(β_j′=0.570)、随访期间WML加重程度(β_j′=0.244)、糖尿病(β_j′=0.171)。结论 糖尿病可使WML伴MCI患者认知功能进一步减退。重度WML伴MCI的糖尿病患者应作为痴呆的高危人群进行早期干预。     

Demyelination Induces the Decline of the Myelinated Fiber Length in Aged Rat White Matter

To determine the exact reason for the age‐related decline of the myelinated fiber length in white matter, we performed this study. In middle‐aged rats, there was age‐related loss of the unmyelinated fibers with large diameters. The demyelination of the myelinated fibers with small diameters in middle‐aged rat white matter might make the age‐related decrease of the unmyelinated fibers with small diameters in the white matter unnoticeable. However, in old‐aged female rats, the unmyelinated fibers with large and small diameters significantly degenerated together and that the unmyelinated fibers formed from the demyelination of the myelinated fibers could not replenish the age‐related loss of the unmyelinated fibers in the white matter. In conclusion, this study suggested that demyelination of myelinated fibers with small diameters in aged white matter might be the key mechanism of the significant decline of the myelinated fiber length in aged white matter. Anat Rec, 292:528–535, 2009. © 2009 Wiley‐Liss, Inc.     

The role of cerebral ischemia in Alzheimer's disease

The Alzheimer type of dementia and stroke are known to increase at comparable rates with age. Recent advances suggest that vascular risk factors linked to cerebrovascular disease and stroke in the elderly significantly increase the risk of developing Alzheimer's disease (AD). These include atherosclerosis, atrial fibrillation, coronary artery disease, hypertension, and diabetes mellitus. Moreover, review of various autopsy series shows that 60-90% of AD cases exhibit variable cerebrovascular pathology. Although some vascular lesions such as cerebral amyloid angiopathy, endothelial degeneration, and periventricular white matter lesions are evident in most cases of AD, a third will exhibit cerebral infarction. Despite the interpretation of pathological evidence, longitudinal clinical studies suggest that the co-existence of stroke and AD occurs more than by chance alone. Strokes known to occur in patients with Alzheimer syndrome and most frequently in the oldest old substantially worsen cognitive decline and outcome, implicating some interaction between the disorders. Nevertheless, the nature of a true relationship between the two disorders seems little explored. What predisposes to strokes in underlying cognitive decline or AD? Is it possible that cerebral ischemia is a causal factor for AD? I examined several vascular factors and the vascular pathophysiology implicated in stroke and AD, and propose that cerebral ischemia or oligemia may promote Alzheimer type of changes in the aging brain. Irrespective of the ultimate pathogenetic mechanism, these approaches implicate that management of peripheral vascular disease is important in the treatment or prevention of Alzheimer's disease or mixed dementia.     

Intracranial pulsatility is associated with regional brain volume in elderly individuals

Excessive intracranial pulsatility is thought to damage the cerebral microcirculation, causing cognitive decline in elderly individuals. We investigated relationships between brain structure and measures related to intracranial pulsatility among healthy elderly. Thirty-seven stroke-free, non-demented individuals (62–82 years of age) were included. We assessed brain structure, invasively measured cerebrospinal fluid (CSF) pulse pressure, and magnetic resonance–quantified arterial and CSF flow pulsatility, as well as arterial pulse pressure. Using both multivariate partial least squares and ordinary regression analyses, we identified a significant pattern of negative relationships between the volume of several brain regions and measures of intracranial pulsatility. The strongest relationships concerned the temporal lobe cortex and hippocampus. These findings were also coherent with observations of positive relationships between intracranial pulsatility and ventricular volume. In conclusion, elderly subjects with high intracranial pulsatility display smaller brain volume and larger ventricles, supporting the notion that excessive cerebral arterial pulsatility harms the brain. This calls for research investigating altered intracranial cardiac-related pulsatile stress as a potential risk factor that may cause or worsen the prognosis in subjects developing cognitive impairment and dementia.     

The role of diffusion MRI in neuroscience

Diffusion‐weighted imaging has pushed the boundaries of neuroscience by allowing us to examine the white matter microstructure of the living human brain. By doing so, it has provided answers to fundamental neuroscientific questions, launching a new field of research that had been largely inaccessible. We briefly summarize key questions that have historically been raised in neuroscience concerning the brain's white matter. We then expand on the benefits of diffusion‐weighted imaging and its contribution to the fields of brain anatomy, functional models and plasticity. In doing so, this review highlights the invaluable contribution of diffusion‐weighted imaging in neuroscience, presents its limitations and proposes new challenges for future generations who may wish to exploit this powerful technology to gain novel insights.