Cognitive and functional impairment in hypertensive brain microangiopathy

Microvascular and Macrovascular Abnormalities and Cognitive and Physical Function in Older Adults: Cardiovascular Health Study

OBJECTIVES

To evaluate and compare the associations between microvascular and macrovascular abnormalities and cognitive and physical function

DESIGN

Cross-sectional analysis of the Cardiovascular Health Study (1998-1999).

SETTING

Community.

PARTICIPANTS

Individuals with available data on three or more of five microvascular abnormalities (brain, retina, kidney) and three or more of six macrovascular abnormalities (brain, carotid artery, heart, peripheral artery) (N = 2,452; mean age 79.5).

MEASUREMENTS

Standardized composite scores derived from three cognitive tests (Modified Mini-Mental State Examination, Digit-Symbol Substitution Test, Trail-Making Test (TMT)) and three physical tests (gait speed, grip strength, 5-time sit to stand)

RESULTS

Participants with high microvascular and macrovascular burden had worse cognitive (mean score difference = -0.30, 95% confidence interval (CI) = -0.37 to -0.24) and physical (mean score difference = -0.32, 95% CI = -0.38 to -0.26) function than those with low microvascular and macrovascular burden. Individuals with high microvascular burden alone had similarly lower scores than those with high macrovascular burden alone (cognitive function: -0.16, 95% CI = -0.24 to -0.08 vs -0.13, 95% CI = -0.20 to -0.06; physical function: -0.15, 95% CI = -0.22 to -0.08 vs -0.12, 95% CI = -0.18 to -0.06). Psychomotor speed and working memory, assessed using the TMT, were only impaired in the presence of high microvascular burden. Of the 11 vascular abnormalities considered, white matter hyperintensity, cystatin C-based glomerular filtration rate, large brain infarct, and ankle-arm index were independently associated with cognitive and physical function.

CONCLUSION

Microvascular and macrovascular abnormalities assessed using noninvasive tests of the brain, kidney, and peripheral artery were independently associated with poor cognitive and physical function in older adults. Future research should evaluate the usefulness of these tests in prognostication.

Freezing of gait and white matter changes: a tract-based spatial statistics study

Background

We hypothesized that the integrity of white matter might be related to the severity of freezing of gait in age-related white matter changes.

Methods

Twenty subjects exhibiting excessive hyperintensities in the periventricular and deep white matter were recruited. The subjects underwent the Freezing of Gait Questionnaire, computerized gait analyses, and diffusion tensor magnetic resonance imaging. Images of axial, radial and mean diffusivity, and fractional anisotropy were calculated as indices of white matter integrity and analyzed with tract-based spatial statistics.

Results

The fractional anisotropy, mean, axial and radial diffusivity averaged across the whole white matter structure were all significantly correlated with Freezing of Gait Questionnaire scores. Regionally, a negative correlation between Freezing of Gait Questionnaire scores and fractional anisotropy was found in the left superior longitudinal fasciculus beneath the left premotor cortex, right corpus callosum, and left cerebral peduncle. The scores of the Freezing of Gait Questionnaire were positively correlated with mean diffusivity in the left corona radiata and right corpus callosum, and with both axial and radial diffusivity in the left corona radiata. The white matter integrity in these tracts (except the corpus callosum) showed no correlation with cognitive or other gait measures, supporting the specificity of those abnormalities to freezing of gait.

Conclusion

Divergent pathological lesions involved neural circuits composed of the cerebral cortex, basal ganglia and brainstem, suggesting that freezing of gait has a multifactorial nature.

Hypertension Accelerates the Progression of Alzheimer-Like Pathology in a Mouse Model of the Disease

Cerebrovascular impairment is frequent in patients with Alzheimer disease and is believed to influence clinical manifestation and severity of the disease. Cardiovascular risk factors, especially hypertension, have been associated with higher risk of developing Alzheimer disease. To investigate the mechanisms underlying the hypertension, Alzheimer disease cross talk, we established a mouse model of dual pathology by infusing hypertensive doses of angiotensin II into transgenic APPPS1 mice overexpressing mutated human amyloid precursor and presenilin 1 proteins. At 4.5 months, at the early stage of disease progression, only hypertensive APPPS1 mice presented impairment of temporal order memory performance in the episodic-like memory task. This cognitive deficit was associated with an increased number of cortical amyloid deposits (223±5 versus 207±5 plaques/mm 2 ; P <0.05) and a 2-fold increase in soluble amyloid levels in the brain and in plasma. Hypertensive APPPS1 mice presented several cerebrovascular alterations, including a 25% reduction in cerebral microvessel density and a 30% to 40% increase in cerebral vascular amyloid deposits, as well as a decrease in vascular endothelial growth factor A expression in the brain, compared with normotensive APPPS1 mice. Moreover, the brain levels of nitric oxide synthase 1 and 3 and the nitrite/nitrate levels were reduced in hypertensive APPPS1 mice (by 49%, 34%, and 33%, respectively, compared with wild-type mice; P <0.05). Our results indicate that hypertension accelerates the development of Alzheimer disease–related structural and functional alterations, partially through cerebral vasculature impairment and reduced nitric oxide production.

Clinical symptoms and risk factors in cerebral microangiopathy patients

OBJECTIVE

Although the clinical manifestation and risk factors of cerebral microangiopathy (CM) remain unclear, the number of diagnoses is increasing. Hence, patterns of association among lesion topography and severity, clinical symptoms and demographic and disease risk factors were investigated retrospectively in a cohort of CM patients.

METHODS

Patients treated at the Department of Neurology, University of Bonn for CM (n = 223; 98m, 125f; aged 77.32±9.09) from 2005 to 2010 were retrospectively enrolled. Clinical symptoms, blood chemistry, potential risk factors, demographic data and ratings of vascular pathology in the brain based on the Wahlund scale were analyzed using Pearson's chi square test and one-way ANOVA.

RESULTS

Progressive cognitive decline (38.1%), gait apraxia (27.8%), stroke-related symptoms and seizures (24.2%), TIA-symptoms (22%) and vertigo (17%) were frequent symptoms within the study population. Frontal lobe WMLs/lacunar infarcts led to more frequent presentation of progressive cognitive decline, seizures, gait apraxia, stroke-related symptoms, TIA, vertigo and incontinence. Parietooccipital WMLs/lacunar infarcts were related to higher frequencies of TIA, seizures and incontinence. Basal ganglia WMLs/lacunar infarcts were seen in patients with more complaints of gait apraxia, vertigo and incontinence. Age (p = .012), arterial hypertension (p<.000), obesity (p<.000) and cerebral macroangiopathy (p = .018) were positively related to cerebral lesion load. For increased glucose level, homocysteine, CRP and D-Dimers there was no association.

CONCLUSION

This underlines the association of CM with neurological symptoms upon admission in a topographical manner. Seizures and vertigo are symptoms of CM which may have been missed in previous studies. In addition to confirming known risk factors such as aging and arterial hypertension, obesity appears to increase the risk as well. Since the incidence of CM is increasing, future studies should focus on the importance of prevention of vascular risk factors on its pathogenesis.

Retinal microvascular signs and disability in the Cardiovascular Health Study

OBJECTIVE

To study the associations of retinal microvascular changes, which are associated with systemic conditions and cognitive decline, with disability in performing activities of daily living (ADL).

DESIGN

Prospective cohort study of 1487 community-dwelling participants in the Cardiovascular Health Study (mean age, 78 years) who were free of ADL disability and had available data on retinal signs and carotid intima-media thickness at the 1998-1999 visit. Main outcome measures were incident ADL disability, defined as self-reported difficulty in performing any ADL, by the presence of retinal signs and advanced carotid atherosclerosis, defined by carotid intima-media thickness in the 80th percentile or more or 25% or more stenosis, and potential mediation by cerebral microvascular disease on brain imaging or by executive dysfunction, slow gait, and depressive mood, which are symptoms of frontal subcortical dysfunction.

RESULTS

During the median follow-up of 3.1 years (maximum, 7.8 years), participants with 2 or more retinal signs had a higher rate of disability than those with fewer than 2 retinal signs (10.1% vs 7.1%; adjusted hazard ratio, 1.45; 95% confidence interval, 1.24-1.69; P < .001). There was no evidence of interaction by advanced carotid atherosclerosis (P > .10). The association seemed to be partially mediated by executive dysfunction, slow gait, and depressive symptoms but not by cerebral microvascular disease on brain imaging.

CONCLUSIONS

These results provide further support for the pathophysiologic and prognostic significance of microvascular disease in age-related disability. However, it remains to be determined how to best use retinal photography in clinical risk prediction.

Is Alzheimer's disease amyloidosis the result of a repair mechanism gone astray?

Here, we synthesize several lines of evidence supporting the hypothesis that at least one function of amyloid-β is to serve as a part of the acute response to brain hemodynamic disturbances intended to seal vascular leakage. Given the resilient and adhesive physicochemical properties of amyloid, an abluminal hemostatic repair system might be highly advantageous, if deployed on a limited and short-term basis, in young individuals. However, in the aged, inevitable cardiovascular dysfunction combined with brain microvascular lesions may yield global chronic hypoperfusion that may lead to continuous amyloid deposition and consequential negative effects on neuronal viability. A large body of experimental evidence supports the hypothesis of an amyloid-β rescue function gone astray. Preventing or inducing the removal of amyloid in Alzheimer's disease (AD) has been simultaneously successful and disappointing. Amyloid deposits clearly play major roles in AD, but they may not represent the preeminent factor in dementia pathogenesis. Successful application of AD preventative approaches may hinge on an accurate and comprehensive view of comorbidities, including cardiovascular disease, diabetes, and head trauma.

White matter hyperintensities and impaired choice stepping reaction time in older people

White matter hyperintensities (WMHs) are associated with impaired mobility in older people, but no studies have identified neuropsychological and sensorimotor mediating factors for this association. Our objective was to determine whether neuropsychological and sensorimotor functions mediate the association of WMHs and choice stepping reaction time (CSRT) under standard and dual-task conditions using structural equation modeling. Two hundred fifty-four older community dwellers (77.8 ± 4.5 years) underwent structural magnetic resonance imaging, CSRT tests, neuropsychological and sensorimotor assessments. WMH volumes were quantified using an automated method. WMH volumes were significantly associated with neuropsychological tests and dual task CSRT performance. All neuropsychological and sensorimotor variables were also significantly associated with standard and dual task CSRT. The structural equation modeling revealed that impaired sensorimotor function was the only factor influencing impaired stepping performances in the standard condition. In the dual task condition, the association between WMHs and CSRT was mediated through slowed cognitive processing and not through reduced sensorimotor functioning. The conclusion was that WMHs are associated with slowed performance on a dual task CSRT task and this relationship is explained primarily by underlying neuropsychological impairments.

Gait disturbance associated with white matter changes: a gait analysis and blood flow study

To clarify the mechanisms underlying gait disturbance secondary to age-related white matter changes (ARWMC), cerebral perfusion was investigated during treadmill walking. Twenty subjects with extensive hyperintensities in the periventricular and deep white matter on T(2)-weighted magnetic resonance images (MRI) were recruited. The ARWMC subjects were classified into gait-disturbed (GD) and non-GD groups according to clinical criteria. All the subjects underwent gait analyses and cerebral perfusion measurements during both gait and rest by using single photon emission computed tomography. The GD group showed greater double support time/phase and stride width, and slower walking velocity, than the non-GD group. In an analysis of pooled data from all the subjects, gait-induced increases in cerebral perfusion were observed in the supplementary motor areas (SMA), lateral premotor cortex (PMC), primary motor and somatosensory areas, visual areas, basal ganglia and cerebellum. A between-group comparison of gait-induced perfusion changes showed relative underactivation of the SMA, thalamus and basal ganglia, together with relative overactivation of the PMC, in the GD group compared with the non-GD group. In a separate correlation analysis including all the subjects, as the double support phase was longer (that was, gait disturbance was more severe), the gait-induced perfusion changes were proportionally reduced in the SMA, visual cortex, and thalamus. The present study suggests that abnormalities in the basal ganglia-thalamo-cortical loops partly explain gait disturbance observed in a subset of subjects with ARWMC.

Brain flexibility and balance and gait performances mark morphological and metabolic abnormalities in the elderly

Although previous studies have found that cerebral white matter hyperintensities are associated with balance-gait disorders, no proton magnetic resonance spectroscopy data at the plane of the basal ganglia have been published. We investigated a possible relationship between balance performance and brain metabolite ratios or structural MRI measurements. We also included neuropsychological tests to determine whether such tests are related to structural or metabolic findings. All 80 participants were taken from the cohort of the Three-City study (Dijon-Bordeaux-Montpellier, France). The ratios of N-acetyl-aspartate to creatine (NAA/Cr) and choline to creatine (Cho/Cr) were calculated in the basal ganglia, thalami and insular cortex. We used univariate regression to identify which variables predicted changes in NAA/Cr and Cho/Cr, and completed the analysis with a multiple linear or logistic regression. After the multivariate analysis including hypertension, age, balance-gait, sex, white matter lesions, brain atrophy and body mass index, only balance-gait performance remained statistically significant for NAA/Cr (p=0.01) and for deep white-matter lesions (p=0.02). The Trail-Making Test is independently associated with brain atrophy and periventricular white-matter hyperintensities. Neuronal and axonal integrity at the plane of the basal ganglia is associated with balance and gait in the elderly, whereas brain flexibility is associated with structural MRI brain abnormalities.