Subcortical ischaemic vascular dementia

Altered functional connectivity in patients with subcortical ischemic vascular disease: A resting-state fMRI study

Patients with subcortical ischemic vascular disease (SIVD) may hold a high risk of cognitive impairment (CI) by affecting the functional connectivity (FC) of resting-state networks (RSNs). Current studies have mainly focused on the patients with CI but have ignored the prodromal stage when people suffered subcortical vascular damage, but without CI. Independent component analysis (ICA) of rs-fMRI could detect altered FC in RSNs at the early stage of the disease. 81 SIVD patients with CI (SVCI = 29) and without CI (pre-SVCI = 25), and 27 normal controls (NCs) were scanned with rs-fMRI, analyzed by ICA and assessed by neuropsychological examinations. We found significantly altered FC within the RSNs of sensorimotor network (SMN), posterior default mode networks (pDMN), right frontoparietal network (rFPN) and language network (LN) (P < 0.05, AlphaSim corrected). The pre-SVCI group showed significantly increased FC in brain regions of the multiple RSNs when compared with the other two groups. The mean values extracted from the right inferior frontal gyrus (IFG.R) and the left posterior cingulate gyrus (PCG.L) were significantly correlated with clock drawing test (CDT). The right precentral/postcentral gyrus (PreCG.R/PoCG.R) and the right supramarginal gyrus (SMG.R) were positively correlated with Stroop-1 Test. We concluded the FC in RSNs had already been changed at the early stage of the disease as the maladaptive response or compensatory reallocation of the cognitive resources. The ICA of rs-fMRI can be applied as a potential approach to identify the underlying mechanisms of SIVD.

Chronic cerebral hypoperfusion shifts the equilibrium of amyloid β oligomers to aggregation-prone species with higher molecular weight

Epidemiological studies have shown that atherosclerotic risk factors accelerate the pathological process underlying Alzheimer’s disease (AD) via chronic cerebral hypoperfusion. In this study, we aimed to clarify the mechanisms by which cerebral hypoperfusion may exacerbate AD pathology. We applied bilateral common carotid artery stenosis (BCAS) to a mice model of AD and evaluated how the equilibrium of amyloid β oligomers respond to hypoperfusion. BCAS accelerated amyloid β (Aβ) convergence to the aggregation seed, facilitating the growth of Aβ plaques, but without changing the total Aβ amount in the brain. Furthermore, Aβ oligomers with high molecular weight increased in the brain of BCAS-operated mice. Considering Aβ is in an equilibrium among monomeric, oligomeric, and aggregation forms, our data suggest that cerebral hypoperfusion after BCAS shifted this equilibrium to a state where a greater number of Aβ molecules participate in Aβ assemblies to form aggregation-prone Aβ oligomers with high molecular weight. The reduced blood flow in the cerebral arteries due to BCAS attenuated the dynamics of the interstitial fluid leading to congestion, which may have facilitated Aβ aggregation. We suggest that cerebral hypoperfusion may accelerate AD by enhancing the tendency of Aβ to become aggregation-prone.

Executive Dysfunction Detected with the Frontal Assessment Battery in Alzheimer's Disease Versus Vascular Dementia

Alzheimer's disease (AD) and vascular dementia (VaD) lead to progressive decline in executive function. We estimated the prevalence of executive dysfunction in AD and VaD patients, investigating cognitive, functional, and clinical correlates and also using a multidimensional approach based on a standardized comprehensive geriatric assessment (CGA). We included 215 patients (115 AD patients and 100 VaD patients) consecutively evaluated with a complete cognitive and affective assessment, a CGA, and the Frontal Assessment Battery (FAB) with six subtests investigating conceptualization, mental flexibility, motor programming, sensitivity to interference, inhibitory control, and environmental autonomy. The prevalence of dysexecutive syndrome screened with a FAB score <12 points was high in both AD (97 patients) and VaD (77 patients) (84.3% versus 77.0%, p = 0.171). AD patients were significantly younger, with higher grade of cognitive impairment and less severe comorbidity and polypharmacy than VaD patients. AD patients showed a significantly higher impairment in FAB total score and five FAB subtests (conceptualization, motor programming, sensitivity to interference, inhibitory control, and environmental autonomy) than VaD patients. These findings were largely confirmed in a sub-analysis conducted subdividing the sample in mild and moderate-to-severe demented patients and suggesting that in moderate-to-severe AD there was higher impairment in FAB total score and four FAB subtests (conceptualization, sensitivity to interference, inhibitory control, and environmental autonomy). Executive dysfunction could be greater in AD patients with moderate-to-severe dementia compared to VaD patients, although our groups were also not matched for age, comorbidity or polypharmacy, which could also exert an effect.

Multimodal imaging analyses in patients with genetic and sporadic forms of small vessel disease

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is thought to be a pure genetic form of subcortical vascular cognitive impairment (SVCI). The aim of this study was to compare white matter integrity and cortical thickness between typical CADASIL, a genetic form, and two sporadic forms of SVCI (with NOTCH3 and without NOTCH3 variants). We enrolled typical CADASIL patients (N = 11) and SVCI patients [with NOTCH3 variants (N = 15), without NOTCH3 variants (N = 101)]. To adjust the age difference, which reflects the known difference in clinical and radiologic courses between typical CADASIL patients and SVCI patients, we constructed a W-score of measurement for diffusion tensor image and cortical thickness. Typical CADASIL patients showed more frequent white matter hyperintensities in the bilateral posterior temporal region compared to SVCI patients (p < 0.001, uncorrected). We found that SVCI patients, regardless of the presence of NOTCH3 variants, showed significantly greater microstructural alterations (W-score, p < 0.05, FWE-corrected) and cortical thinning (W-score, p < 0.05, FDR-corrected) than typical CADASIL patients. In this study, typical CADASIL and SVCI showed distinct anatomic vulnerabilities in the cortical and subcortical structures. However, there was no difference between SVCI with NOTCH3 variants and SVCI without NOTCH3 variants.

Alterations of White Matter Integrity in Subcortical Ischemic Vascular Disease with and Without Cognitive Impairment: a TBSS Study

Patients with subcortical ischemic vascular disease (SIVD) may exhibit a high risk of cognitive impairment (CI) by disruption of white matter (WM) integrity. Diffusion tensor imaging (DTI) is recommended as a sensitive method to explore whole brain WM alterations at an asymptomatic stage of the disease, which might be correlated with underlying cognitive disorders. We aim to investigate alterations in WM microstructures and evaluate the relationships between the mean values of diffusion metrics (FA, MD, AD, and RD) and cognitive assessments in SIVD patients. Fifty SIVD patients with (SVCI, N = 25) and without (pre-SVCI, N = 25) cognitive impairments and normal controls (NC, N = 23) underwent DTI and neuropsychological examinations. DTI data were analyzed via TBSS to detect significant changes in WM tracts. Spearman correlation analysis was performed to evaluate relationships between the mean values of diffusion indices and the cognitive assessments. In general, extensive symmetrically altered areas that involved approximately the entire cerebral WM were noted in the pre-SVCI group but were less distinct than that noted in the SVCI group compared with NCs. The genu of corpus callosum exhibited the most damaged WM fiber. Throughout WM, FA was decreased, whereas MD, AD, and RD were increased. Some specific WM tracts in patient groups were significantly correlated with the severity of white matter hyperintensity (WMH), cognitive assessments about executive functions and processing speed. WM integrity has already been damaged at the pre-SVCI stage, which would be associate with future cognitive dysfunction. DTI could potentially establish early biomarkers to detect underlying mechanisms of SIVD.

The Prophylactic and Therapeutic Effects of Fermented Cordyceps sinensis Powder, Cs-C-Q80, on Subcortical Ischemic Vascular Dementia in Mice

Corbrin Capsule, a preparation of Cordyceps sinensis analogue, is a pleiotropic traditional Chinese patent medicine with the main component of fermentative cordyceps fungus powder (Cs-C-Q80). The neuroprotective effects of Cs-C-Q80, as a substitution of Cordyceps sinensis, have not been fully identified. The objectives of this study were to explore the prophylactic and therapeutic effects of Cs-C-Q80 in vascular dementia mice model. The efficacy of Cs-C-Q80 was investigated in a molecular level as well. The subcortical ischemic vascular dementia was modelled by permanent right unilateral common carotid arteries occlusion (rUCCAO) in adult male mice. The animals were randomly divided and treated by gavage with vehicle (1% CMC-Na solution) (rUCCAO model) or Cs-C-Q80 powder at 0.2 g/kg or 1.0 g/kg, respectively. Preventive treatment was administrated by gavage daily for 7 days before rUCCAO, while therapeutic treatment was administrated continuously from 28 days after rUCCAO. Object recognition test and Morris water maze test were performed to evaluate the learning and working memory. The luxol fast blue stain (Kluver-Barrera method) and immunohistochemistry for myelin basic protein (MBP) were employed to determine the severity of white matter damage. Both preventive and therapeutic treatment with Cs-C-Q80 protected against the rUCCAO-induced memory impair in mice as determined by object recognition and Morris water maze tests. The histopathological analyses revealed significant white matter rarefaction and reduction of MBP expression in corpus callosum after rUCCAO, which could be counteracted by either preventive or therapeutic treatment with Cs-C-Q80. Moreover, the Cs-C-Q80 treatments inhibited rUCCAO-induced astrocytes activation and the tumor necrosis factor α (TNF-α) and interleukin-1β expression, indicating the anti-inflammatory roles of Cs-C-Q80 against subcortical ischemia. Cs-C-Q80 is a potential preparation for the prophylaxis and treatment of subcortical ischemic vascular dementia. The underlying pharmacological efficacy might be associated with suppression of myelin degeneration, glia activation, and inflammatory cytokines release.

[Dynamics of the cognitive sphere indicators and neurotrophic factors in the course of balneotherapy of dyscirculatory encephalopathy]

BACKGROUND

The natural factors of therapeutic significance play an important role in the rehabilitation of the patients suffering from chronic disorders of cerebral circulation since they are known to promote the development of the compensatory and adaptive processes. However, there is virtually no information in the relevant literature publications about the influence of balneotherapy on the dynamics of the cognitive sphere indicators and neurotrophic factors.

AIMS

The objective of the present study was to evaluate the effectiveness of balneotherapy as a component of the combined treatment of the patients presenting with discirculatory encephalopathy based on the investigations into dynamics of the neuropsychological status and the quantitative content of the neurotrophic factors in the peripheral blood, with special reference to the brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CNTF), in the patients receiving the balneotherapeutic treatment based at they at the 'Kluchi' health resort.

MATERIAL AND METHODS

A total of 72 patients presenting with the 1st and 2nd stages of chronic cerebral ischemia were examined (including 9 men and 63 women at the mean age of 62.2±2.1 years). They were given the health resort -based treatment during 14 days while staying at the 'Kluchi' resort located in the Perm region. The examination of all the patients included the psychometric testing and the determination of blood serum neurotrophic factors (BDNF and CNTF). The patients were allocated to three groups depending on the character of the prescribed treatment. The first group consisted of 29 subjects, who were given the conventional therapy (the alternation of hydrogen sulphide muds and baths number 7, daily massage of the neck-collar region in the combination with exercise therapy). The second group was comprised of 32 persons who received the standard course of chloride-sodium bromine baths number 7. The third group was composed of 11 persons suffering from chronic cerebral ischemia who received no balneo- or peloid therapy whatever.

RESULTS

The study has revealed the different stages of cognitive and emotional disorders combined with the initially reduced level of BDNF in the blood serum of the examined patients. The level of BDNF in the peripheral blood of the patients comprising the first group increased from 3.68±2.15 to 5.02±2.88 ng/ml after the course of balneotherapy. These values were significantly higher than before the treatment (p=0.000). In the patients of the second group, the level of situational and personal anxiety estimated with the use of the Spielberger-Khanin test decreased in association with the improvement in the cognitive sphere after they received the standard course of balneotherapy including the usual chloride-sodium bromine baths. Simultaneously, the level of BDNF in the peripheral blood of these patents increased from 4.00±2.3 to 5.39±2.44 ng/ml (p=0.02). The patients of the third group, who were given no treatment whatever displayed no statistically significant changes of the studied parameters.

CONCLUSION

The health resort-based treatment including the course of chloride-sodium bromine baths has a direct beneficial influence on the neuroreparative and neuroprotective functions in the patients presenting with chronic cerebral ischemia owing to the increase in the level of neurotrophic factors in the blood.

Contributions of sex to cerebrovascular function and pathology

Sex differences exist in how cerebral blood vessels function under both physiological and pathological conditions, contributing to observed sex differences in risk and outcomes of cerebrovascular diseases (CBVDs), such as vascular contributions to cognitive impairment and dementia (VCID) and stroke. Throughout most of the lifespan, women are protected from CBVDs; however, risk increases following menopause, suggesting sex hormones may play a significant role in this protection. The cerebrovasculature is a target for sex hormones, including estrogens, progestins, and androgens, where they can influence numerous vascular functions and pathologies. While there is a plethora of information on estrogen, the effects of progestins and androgens on the cerebrovasculature are less well-defined. Estrogen decreases cerebral tone and increases cerebral blood flow, while androgens increase tone. Both estrogens and androgens enhance angiogenesis/cerebrovascular remodeling. While both estrogens and androgens attenuate cerebrovascular inflammation, pro-inflammatory effects of androgens under physiological conditions have also been demonstrated. Sex hormones exert additional neuroprotective effects by attenuating oxidative stress and maintaining integrity and function of the blood brain barrier. Most animal studies utilize young, healthy, gonadectomized animals, which do not mimic the clinical conditions of aging individuals likely to get CBVDs. This is also concerning, as sex hormones appear to mediate cerebrovascular function differently based on age and disease state (e.g. metabolic syndrome). Through this review, we hope to inspire others to consider sex as a key biological variable in cerebrovascular research, as greater understanding of sex differences in cerebrovascular function will assist in developing personalized approaches to prevent and treat CBVDs.

Periodontal Ehlers-Danlos syndrome is associated with leukoencephalopathy

Here, we report brain white matter alterations in individuals clinically and genetically diagnosed with periodontal Ehlers-Danlos syndrome, a rare disease characterized by premature loss of teeth and connective tissue abnormalities. Eight individuals of two families clinically diagnosed with periodontal Ehlers-Danlos syndrome were included in the present study and underwent general physical, dental, and neurological examination. Whole exome sequencing was performed, and all patients included in the study underwent MRI of the brain. Whole exome sequencing revealed heterozygous C1R mutations c.926G>T (p.Cys309Phe, Family A) and c.149_150TC>AT (p.Val50Asp, Family B). All adult individuals (n = 7; age range 31 to 68 years) investigated by MRI had brain white matter abnormalities. The MRI of one investigated child aged 8 years was normal. The MRI pattern was suggestive of an underlying small vessel disease that is progressive with age. As observed in other leukoencephalopathies related to microangiopathies, the extent of the white matter changes was disproportionate to the neurologic features. Medical history revealed recurrent headaches or depression in some cases. Neurological examination was unremarkable in all individuals but one had mild cognitive decline and ataxia and experienced a seizure. The observation that periodontal Ehlers-Danlos syndrome caused by missense mutations in C1R is consistently associated with a leukoencephalopathy opens a new pathogenic link between the classical complement pathway, connective tissue, brain small vessels, and brain white matter abnormalities.

Deficiency of TLR4 ameliorates hypoperfusion-induced brain pathology

Microglial inflammatory activation contributes to chronic cerebral hypoperfusion-induced brain pathology. This editorial highlights a study by Qin et al. (Theranostics 2018; 8(19):5434-5451. doi:10.7150/thno.27882) that deficiency of TLR4 attenuates cognitive dysfunction and white matter injury by reducing autophagy and pro-inflammatory activation in microglia.

Memory decline in elderly with cerebral small vessel disease explained by temporal interactions between white matter hyperintensities and hippocampal atrophy

White matter hyperintensities (WMH) constitute the visible spectrum of cerebral small vessel disease (SVD) markers and are associated with cognitive decline, although they do not fully account for memory decline observed in individuals with SVD. We hypothesize that WMH might exert their effect on memory decline indirectly by affecting remote brain structures such as the hippocampus. We investigated the temporal interactions between WMH, hippocampal atrophy and memory decline in older adults with SVD. Five hundred and three participants of the RUNDMC study underwent neuroimaging and cognitive assessments up to 3 times over 8.7 years. We assessed WMH volumes semi-automatically and calculated hippocampal volumes (HV) using FreeSurfer. We used linear mixed effects models and causal mediation analyses to assess both interaction and mediation effects of hippocampal atrophy in the associations between WMH and memory decline, separately for working memory (WM) and episodic memory (EM). Linear mixed effect models revealed that the interaction between WMH and hippocampal volumes explained memory decline (WM: β = .067; 95%CI[.024-0.111]; p < .01; EM: β = .061; 95%CI[.025-.098]; p < .01), with better model fit when the WMH*HV interaction term was added to the model, for both WM (likelihood ratio test, χ² [1] = 9.3, p < .01) and for EM (likelihood ratio test, χ² [1] = 10.7, p < .01). Mediation models showed that both baseline WMH volume (β = -.170; p = .001) and hippocampal atrophy (β = 0.126; p = .009) were independently related to EM decline, but the effect of baseline WMH on EM decline was not mediated by hippocampal atrophy (p value indirect effect: 0.572). Memory decline in elderly with SVD was best explained by the interaction of WMH and hippocampal volumes. The relationship between WMH and memory was not causally mediated by hippocampal atrophy, suggesting that memory decline during aging is a heterogeneous condition in which different pathologies contribute to the memory decline observed in elderly with SVD.

Relationships among clinic, home, and ambulatory blood pressures with small vessel disease of the brain and functional status in older people with hypertension

BACKGROUND

Subcortical small vessel disease, represented as white matter hyperintensity (WMH) on magnetic resonance images (MRI) is associated with functional decline in older people with hypertension. We evaluated the relationships of clinic and out-of-office blood pressures (BP) with WMH and functional status in older persons.

METHODS

Using cross-sectional data from 199 older study participants enrolled in the INFINITY trial, we analyzed the clinic, 24-hour ambulatory, and home BPs and their relationships with WMH burden and mobility and cognitive outcomes.

RESULTS

Volume of WMH was associated with clinic and 24-hour ambulatory systolic BP but not home systolic BP. The mobility measure, supine-to-sit time, had a significant association with 24-hour systolic BP and pulse pressure but not with diastolic BP or values obtained by home BP. Cognitive measures of processing speed (Trails Making Test Part A and the Stroop Word Test) were significantly associated with 24-hour systolic BP, but not clinic and home BPs.

CONCLUSION

These data demonstrate that ambulatory BP measurements in older people are more strongly associated with WMH and certain measures of functional status compared to home BP measurements. Hence, home BP may not be a useful substitute for ambulatory BP for assessing subcortical small vessel disease and its consequences. Further longitudinal analyses comparing clinic and various types of out-of-office BP measures with small vessel brain disease are needed. Clinicaltrials.gov identifier: NCT01650402.

Convergent, Discriminant, and Concurrent Validity of Nonmemory-Based Performance Validity Tests

To supplement memory-based Performance Validity Tests (PVTs) in identifying noncredible performance, we examined the validity of the two most commonly used nonmemory-based PVTs—Dot Counting Test (DCT) and Wechsler Adult Intelligence Scale–Fourth edition (WAIS-IV) Reliable Digit Span (RDS)—as well as two alternative WAIS-IV Digit Span (DS) subtest PVTs. Examinees completed DCT, WAIS-IV DS, and the following criterion PVTs: Test of Memory Malingering, Word Memory Test, and Word Choice Test. Validity groups were determined by passing 3 (valid; n = 69) or failing ⩾2 (noncredible; n = 30) criterion PVTs. DCT, RDS, RDS–Revised (RDS-R), and WAIS-IV DS Age-Corrected Scaled Score (ACSS) were significantly correlated (but uncorrelated with memory-based PVTs). Combining RDS, RDS-R, and ACSS with DCT improved classification accuracy (particularly for DCT/ACSS) for detecting noncredible performance among valid-unimpaired, but largely not valid-impaired examinees. Combining DCT with ACSS may uniquely assess and best supplement memory-based PVTs to identify noncredible neuropsychological test performance in cognitively unimpaired examinees.

The impact of education on cortical thickness in amyloid-negative subcortical vascular dementia: cognitive reserve hypothesis

Background

The protective effect of education has been well established in Alzheimer’s disease, whereas its role in patients with isolated cerebrovascular diseases remains unclear. We examined the correlation of education with cortical thickness and cerebral small vessel disease markers in patients with pure subcortical vascular mild cognitive impairment (svMCI) and patients with pure subcortical vascular dementia (SVaD).

Methods

We analyzed 45 patients with svMCI and 47 patients with SVaD with negative results on Pittsburgh compound B positron emission tomographic imaging who underwent structural brain magnetic resonance imaging. The main outcome was cortical thickness measured using surface-based morphometric analysis. We also assessed the volumes of white matter hyperintensities (WMH) and numbers of lacunes as other outcomes. To investigate the correlation of education with cortical thickness, WMH volume, and number of lacunes, multiple linear regression analyses were performed after controlling for covariates, including Mini Mental State Examination, in the svMCI and SVaD groups.

Results

In the SVaD group, higher education was correlated with more severe cortical thinning in the bilateral dorsolateral frontal, left medial frontal, and parahippocampal areas, whereas there was no correlation of education with cortical thickness in the svMCI group. There was no correlation between education and cerebral small vessel disease, including WMH and lacunes, in both patients with svMCI and patients with SVaD.

Conclusions

Our findings suggest that the compensatory effects of education on cortical thinning apply to patients with SVaD, which might be explained by the cognitive reserve hypothesis.

Magnetic resonance imaging and neuropsychological correlates of subcortical vascular dementia

Common understanding of dementia is mostly based on the Alzheimer's disease model. However, in subcortical vascular dementia (SVaD), several other cognitive and behavioral dysfunctions predominate over what is commonly noticed in Alzheimer's disease. There are inconsistencies in literature regarding the profile of cognitive impairments in vascular dementia.

Postmortem brain MRI is related to cognitive decline, independent of cerebral vessel disease in older adults

The purpose of this study was to determine whether metrics of brain tissue integrity derived from postmortem magnetic resonance imaging (MRI) are associated with late-life cognitive decline, independent of cerebral vessel disease. Using data from 554 older adults, we used voxelwise regression to identify regions where the postmortem MRI transverse relaxation rate constant R2 was associated with the rate of decline in global cognition. We then used linear mixed models to investigate the association between a composite R2 measure and cognitive decline, controlling for neuropathology including 3 indices of vessel disease: atherosclerosis, arteriolosclerosis, and cerebral amyloid angiopathy. This composite R2 measure was associated with the rate of decline (0.049 unit annually per R2 unit, p < 0.0001) and accounted for 6.1% of its variance, beyond contributions from vessel disease indices and other prominent age-related neuropathologies. Thus, postmortem brain R2 reflects disease processes underlying cognitive decline that are not captured by vessel disease indices or other standard neuropathologic indices and may provide a measure of brain tissue integrity that is complementary to histopathologic evaluation.

Visualization of the lenticulostriate arteries at 3T using black-blood T1-weighted intracranial vessel wall imaging: comparison with 7T TOF-MRA

OBJECTIVES

The objective of this study was to explore the feasibility of using intracranial T1-weighted vessel wall imaging (VWI) to visualize the lenticulostriate arteries (LSAs) at 3T.

MATERIAL AND METHODS

Thirteen healthy volunteers were examined with VWI at 3T and TOF-MRA at 7T during the same day. On the vascular skeletons obtained by manual tracing, the number of stems and branches of LSAs were counted. On the most prominent branch in every hemisphere, the contrast-to-noise ratio (CNR), the full length and the local length (5-15 mm above MCAs) were measured and compared between the two methods. Nine stroke patients with intracranial artery stenosis were also recruited into the study. The branches of LSAs were compared between the symptomatic and asymptomatic side.

RESULTS

The extracted vascular trees were in good agreement between 7T TOF-MRA and 3T VWI. The two acquisitions showed similar numbers of the LSA stems. The number of branches revealed by 3T VWI was slightly lower than 7T TOF. The full lengths were slightly lower by VWI at 3T (p = 0.011, ICC = 0.917). The measured local lengths (5-15 mm from MCAs) showed high coherence between VWI and TOF-MRA (p = 0.098, ICC = 0.970). In stroke patients, 12 plaques were identified on MCA segments, and nine plaques were located on the symptomatic side. The average numbers of LSA visualized by 3T VWI were 4.3±1.3 on the symptomatic side and 5.0±1.1 on the asymptomatic side.

CONCLUSION

3T VWI is capable of depicting LSAs, particularly the stems and the proximal segments, with comparable image quality to that of 7T TOF-MRA.

KEY POINTS

• T1-weighted intracranial VWI at 3T allows for black-blood MR angiography of lenticulostriate artery. • 3T intracranial VWI depicts the stems and proximal segments of the lenticulostriate arteries comparable to 7T TOF-MRA. • It is feasible to assess both large vessel wall lesions and lenticulostriate vasculopathy in one scan.

Disorders of the immune status in patients with chronic cerebral ischemia; differentiated pharmacological correction

Introduction: Chronic cerebral ischemia (CCI) accounts for 60-75% of all cerebrovascular diseases in Russia and around the world. The problem: the issues concerning the role of immunity in the pathogenesis of CCI depending on the main etiologic factor and stage of the disease are hardly elaborated, which makes the main pharmacological correction impossible. The objective of the study is to establish the immune disorder patterns in patients with CCI I-II associated with arterial hypertension and to develop differentiated pharmacological methods for their correction.

Material and methods: The results of treatment of 104 patients of Kursk Regional Clinical Hospital with CCI associated with II-stage arterial hypertension were analyzed: 52 patients were with CCI I stage (2th-4th groups of 12-14 patients) and 52 patients were with CCI II stage (5th -7th groups of 12-14 patients), aged 50±5, who received the basic pharmacological therapy (enalapril and vinpocetine). The patients of the 2nd and 5th groups additionally received ceraxon and mexicor, those of the 3rd and the 6th groups additionally received immunomodulator glutoxim, and those from the 4th and 7th groups received polyoxidonium. Twenty-two healthy donors were in the control group. Immune disorders were assessed by the parameters of the functional activity of neutrophils, levels of cytokines in plasma, components of the complement and inhibitors.

Results and discussion: In the case of CCI I and II stages similar proinflamatory immune disorders were detected, which is indicative of immune inflammation. The inclusion of glutoxime and polyoxidonium in a complex pharmacotherapy helps reduce the severity of immune and neuropsychic status indicators, which are more evident in case of stage II.

Conclusions: In case of CCI I stage, the medications used can be arranged according to their clinico-immunological efficacy in ascending order: ceraxon+mexicore ® ceraxon+mexicor+glutoxim ® ceraxon+mexicor+polyoxidonium, and in case of CCI II stage: ceraxon+mexicor ® ceraxon+mexicor+polyoxidonium = ceraxon+mexicor+glutoxim.

Estradiol Protects White Matter of Male C57BL6J Mice against Experimental Chronic Cerebral Hypoperfusion

BACKGROUND AND PURPOSE

Estradiol is a sex steroid hormone known to protect the brain against damage related to transient and global cerebral ischemia. In the present study, we leverage an experimental murine model of bilateral carotid artery stenosis (BCAS) to examine the putative effects of estradiol therapy on chronic cerebral hypoperfusion. We hypothesize that long-term estradiol therapy protects against white matter injury and declarative memory deficits associated with chronic cerebral hypoperfusion.

METHODS

Adult male C57BL/6J mice underwent either surgical BCAS or sham procedures. Two days after surgery, the mice were given oral estradiol (Sham+E, BCAS+E) or placebo (Sham+P, BCAS+P) treatments daily for 31-34 days. All mice underwent Novel Object Recognition (NOR) testing 31-34 days after the start of oral treatments. Following sacrifice, blood was collected and brains fixed, sliced, and prepared for histological examination of white matter injury and extracellular signal-regulated kinase (ERK) expression.

RESULTS

Animals receiving long-term oral estradiol therapy (BCAS-E2 and Sham-E2) had higher plasma estradiol levels than those receiving placebo treatment (BCAS-P and Sham-P). BCAS-E2 mice demonstrated less white matter injury (Klüver-Barrera staining) and performed better on the NOR task compared to BCAS-P mice. ERK expression in the brain was increased in the BCAS compared to sham cohorts. Among the BCAS mice, the BCAS-E2 cohort had a greater number of ERK + cells.

CONCLUSION

This study demonstrates a potentially protective role for oral estradiol therapy in the setting of white matter injury and declarative memory deficits secondary to murine chronic cerebral hypoperfusion.

Molecular Mechanisms of Oligodendrocyte Regeneration in White Matter-Related Diseases

Even in adult brains, restorative mechanisms are still retained to maintain the microenvironment. Under the pathological conditions of central nervous system (CNS) diseases, several immature cells in the brain would be activated as a compensative response. As the concept of the neurovascular unit emphasizes, cell-cell interactions play important roles in this restorative process. White matter damage and oligodendrocyte loss are representative characteristics for many neurodegenerative diseases. In response to oligodendrocyte damage, residual oligodendrocyte precursor cells (OPCs) initiate their proliferation and differentiation for the purpose of remyelination. Although mechanisms of oligodendrogenesis and remyelination in CNS diseases are still mostly unknown and understudied, accumulated evidence now suggests that support from neighboring cells is necessary for OPC proliferation and differentiation. In this review, we first overview basic mechanisms of interaction between oligodendrocyte lineage cells and neighboring cells, and then introduce how oligodendrogenesis occurs under the conditions of neurodegenerative diseases, focusing on vascular cognitive impairment syndrome, Alzheimer’s disease, and multiple sclerosis.

Enriched Brain Omega-3 Polyunsaturated Fatty Acids Confer Neuroprotection against Microinfarction

Cerebral microinfarcts have significant effects on the development of geriatric neurological disorders, including vascular dementia and Alzheimer's disease. However, little is known about the pathophysiological mechanisms involved in the evolution of microinfarcts and potential treatment and prevention against these microvascular ischemic lesions. In the present study, the "single cortical microinfarct model" generated via occluding a penetrating arteriole by femtosecond laser ablation and the "multiple diffuse microinfarcts model" induced by unilateral injection of cholesterol crystals through the internal carotid artery were established to investigate the pathophysiological mechanisms underlying the evolution of microinfarcts and the effects of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) on alleviating microinfarct burdens and functional deficits. The occlusion of a single penetrating arteriole led to a distinct cortical microinfarct, which manifested as neuronal loss and occupation of activated glial cells in the ischemic core. Using Fat-1 transgenic mice and fish oil supplements, we demonstrated that both endogenously-generated and exogenously-delivered ω-3 PUFAs significantly inhibited the activation of receptor-interacting serine/threonine protein kinases 1 (RIPK1) and its downstream apoptosis-associated proteins, mitigated cell apoptosis, and anatomically reduced the microinfarct size. The protective effects of ω-3 PUFAs against microinfarcts were further verified in a multiple diffuse microinfarcts model, where ω-3 PUFAs significantly attenuated cell apoptosis as revealed by TUNEL staining, alleviated the diffuse microinfarct burdens and remarkably improved the functional deficits as evidenced by reduced spontaneous anxiety, increased preference for the novel object, and improved hippocampal-based learning and short-term memory. Together, these findings demonstrate that enriched brain ω-3 PUFAs are effective for reducing microinfarct burdens and improving the function deficits, which support the clinical research and application of ω-3 PUFAs in the treatment or prophylaxis in vascular dementia.

Associations between lesions and domain-specific cognitive decline in poststroke dementia

Objective

To investigate whether the effect of prestroke and stroke-related lesions on incident poststroke dementia (PSD) is mediated by a unique pattern of domain-specific cognitive impairment, and the relative strength of these anatomical–cognitive associations in predicting incident PSD.

Methods

In this incident case-control study (n = 150), we defined incident cases as acute stroke patients who developed PSD and controls as acute stroke patients who remained free from dementia at a 6 month follow-up, matched on age, prestroke cognitive status, and number of stroke-related lesions. MRI was performed at initial clinical presentation; neuropsychological assessments and clinical diagnosis of PSD was performed 6 months poststroke. Moderated mediation analysis evaluated the interactions among PSD, anatomical lesions, cognitive domains, and individual demographic and medical characteristics.

Results

Compared to stroke-related lesions, prestroke lesions were associated with the widest range of cognitive domain impairments and had stronger clinical utility in predicting incident PSD. Specifically, global cortical atrophy (GCA) and deep white matter hyperintensities (WMH) were indirectly associated with PSD by disrupting executive functions, memory, and language. Acute infarcts were indirectly associated with PSD by disrupting executive functions and language. The strongest mediator was executive dysfunction, increasing risk of PSD in patients with deep WMH, GCA, and large infarcts by more than 9 times, with sex and educational attainment moderating the magnitude of association. Periventricular WMH were directly associated with incident PSD but not mediated by deficits in cognitive domains.

Conclusion

We provide an anatomical–cognitive framework that can be applied to stratify patients at highest risk of PSD and to guide personalized interventions.

Histopathologic features of an autopsied patient with cerebral small vessel disease and a heterozygous HTRA1 mutation

Cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) is a hereditary cerebral small vessel disease (CSVD) caused by homozygous or compound heterozygous mutations of the high temperature requirement A serine peptidase 1 gene (HTRA1). Affected patients suffer from cognitive impairment, recurrent strokes, lumbago and alopecia. Recently, clinical studies have indicated that some patients with heterozygous mutations in HTRA1 may also suffer CSVD. Here, we report the histopathologic features of an autopsied 55-year-old male patient who had shown cognitive impairment and multiple cerebral infarcts, and was found to have a heterozygous missense mutation (p.R302Q) in the HTRA1 gene. Histologically, small vessels in the brain and spinal cord showed intimal proliferation, splitting of the internal elastic lamina, and degeneration of smooth muscle cells in the tunica media. Thus, although less severe, the features were quite similar to those of patients with CARASIL, indicating that patients with heterozygous mutations develop CSVD through underlying pathomechanisms similar to those of CARASIL.

Hippocampal microvasculature changes in association with oxidative stress in Alzheimer's disease

Vascular endothelial dysfunction is a primary phenotype of aging, and microvascular (MV) lesion is mainly associated with Alzheimer's disease (AD). Here we have studied the correlation of MV wall thickness and CA1 pyramidal neuronal pathology in autopsy-confirmed AD brains. Both hyaline (h-MV) and increased cell number (c-MV) associated MV wall thickening was found in age-matched control (AC) hippocampus without significant change in Aβ level (Braak stages 0-III). AC neurons neighboring the h-MV showed lower levels of oxidative DNA/RNA damage and Aβ precursor protein (APP), while the neurons around c-MV showed higher oxidative DNA/RNA damage with increased APP expression. Neurons in AC hippocampus without MV wall thickening (thin wall) showed increased DNA/RNA damage and APP levels compared to AC cases with h-MV and c-MV walls. In the AD hippocampus neurons neighboring h-MV walls showed increased levels of Aβ and decreased number of dendritic spines (at Braak stages IV-VI). C-MV neighboring neurons in the AD cases showed higher levels of DNA/RNA damage with increased APP at stages II - III, followed by lower levels of oxidative DNA/RNA damage, decreased APP and increased Aβ levels with loss of dendritic spines at stages IV-VI. Prolonged treatment of primary human fetal hippocampal neurons with tert-butyl hydroperoxide (TBHP) induced oxidative DNA damage with a sustained increase in APP. Aβ increased rapidly and then decreased overtime. Short-term TBHP treated neurons showed lower levels of superoxide (O₂^{• -}) without significant DNA damage. Short-term TBHP treatment induced a gradual decrease in APP but an increase in Aβ levels over time. In conclusion this study indicates that AD hippocampus at Braak stages II-III are characterized by strong oxidative DNA/RNA damage with increased APP in neurons associated with c-MV, while stages IV-VI are characterized by a slow increase in Aβ in neurons neighboring both h-MV and c-MV.

Effect of treadmill exercise on spatial navigation impairment associated with cerebellar Purkinje cell loss following chronic cerebral hypoperfusion

In addition to roles in motor coordination, the cerebellum is also associated with cognitive function. The aim of the present study was to investigate the effect of treadmill exercise on spatial navigation deficit induced by chronic cerebral hypoperfusion (CCH). Furthermore, whether decreased loss of Purkinje cells, which contain the calcium-binding protein in the posterior lobe of the cerebellum, attenuates the spatial navigation deficit induced by CCH was also investigated. Wistar rats were randomly divided into three groups: Sham group, bilateral common carotid arteries occlusion (BCCAO) group and a BCCAO + exercise (Ex) group. The rats in the BCCAO + Ex group ran on a treadmill for 30 min once a day for 8 weeks, starting at 4 weeks post-birth. CCH was induced by performing BCCAO at 12 weeks post-birth. The Morris water maze test was performed to determine the spatial navigation function of the rats. To investigate the histological features of the cerebellum in all of the experimental groups post-treatment, terminal deoxynucleotidyl transferase dUTP nick end labeling staining, as well as immunohistochemical analysis revealing the expression of calbindin, parvalbumin, glial fibrillary acidic protein, ionized calcium-binding adaptor molecule 1 and caspase-3, was performed. The results of the present study revealed that treadmill exercise improved spatial navigation, decreased the expression of reactive astrocytes and microglial cells, and decreased apoptotic rates in the cerebellar vermis post-CCH. Treadmill exercise also attenuated the loss of Purkinje cells following CCH. The number of Purkinje cells was revealed to be negatively correlated with spatial navigation performance. These results indicate that treadmill exercise may attenuate spatial navigation impairment via inhibition of Purkinje cell loss in the posterior lobe of the cerebellum following CCH. Therefore, treadmill exercise may represent a therapeutic strategy for the treatment of patients with spatial navigation impairment following CCH.

Both Reaction Time and Accuracy Measures of Intraindividual Variability Predict Cognitive Performance in Alzheimer's Disease

Dementia researchers around the world prioritize the urgent need for sensitive measurement tools that can detect cognitive and functional change at the earliest stages of Alzheimer's disease (AD). Sensitive indicators of underlying neural pathology assist in the early detection of cognitive change and are thus important for the evaluation of early-intervention clinical trials. One method that may be particularly well-suited to help achieve this goal involves the quantification of intraindividual variability (IIV) in cognitive performance. The current study aimed to directly compare two methods of estimating IIV (fluctuations in accuracy-based scores vs. those in latency-based scores) to predict cognitive performance in AD. Specifically, we directly compared the relative sensitivity of reaction time (RT)-and accuracy-based estimates of IIV to cognitive compromise. The novelty of the present study, however, centered on the patients we tested [a group of patients with Alzheimer's disease (AD)] and the outcome measures we used (a measure of general cognitive function and a measure of episodic memory function). Hence, we compared intraindividual standard deviations (iSDs) from two RT tasks and three accuracy-based memory tasks in patients with possible or probable Alzheimer's dementia (n = 23) and matched healthy controls (n = 25). The main analyses modeled the relative contributions of RT vs. accuracy-based measures of IIV toward the prediction of performance on measures of (a) overall cognitive functioning, and (b) episodic memory functioning. Results indicated that RT-based IIV measures are superior predictors of neurocognitive impairment (as indexed by overall cognitive and memory performance) than accuracy-based IIV measures, even after adjusting for the timescale of measurement. However, one accuracy-based IIV measure (derived from a recognition memory test) also differentiated patients with AD from controls, and significantly predicted episodic memory performance. The findings suggest that both RT- and accuracy-based IIV measures may be useful indicators of underlying neuropathology. The present study therefore contributes toward an understanding of the relative utility of RT- and accuracy-based IIV measures in detecting neurocognitive impairment in older adults, and also advances the empirical evaluation of sensitive markers of cognitive change in patients with AD.

Cognitive impairment in Parkinson's disease, Alzheimer's dementia, and vascular dementia: the role of the clock-drawing test

AIM

Cognitive impairment is present in several neurodegenerative disorders. The clock-drawing test (CDT) represents a useful screening instrument for assessing the evolution of cognitive decline. The aim of this study was to investigate the sensitivity of the CDT in monitoring and differentiating the evolution of cognitive decline in Alzheimer's dementia (AD), vascular dementia (VaD), and Parkinson's disease (PD).

METHODS

This study involved 139 patients, including 39 patients with PD and mild cognitive impairment, 16 demented PD patients, 21 VaD patients with mild cognitive impairment, 17 patients with VaD, 33 patients with mild cognitive impairment due to AD, and 13 patients with probable AD. All participants completed the CDT. The Mini-Mental State Examination was administered to establish patients' cognitive functioning.

RESULTS

Comparisons of quantitative and qualitative CDT scores showed significant differences between the various diseases. Impairment of executive functioning seems to be more pronounced in PD and VaD than in AD. Patients with AD committed more errors related to a loss of semantic knowledge, indicating a severely reduced capacity in abstract and conceptual thinking.

CONCLUSION

Results support the usefulness and sensitivity of the CDT in the detection of different dementia subtypes. Qualitative error analysis of the CDT may be helpful in differentiating PD, VaD, and AD, even in the early stages of each disease.

Contribution of diffusion, perfusion and functional MRI to the disconnection hypothesis in subcortical vascular cognitive impairment

Vascular cognitive impairment (VCI) describes all forms of cognitive impairment caused by any type of cerebrovascular disease. Early identification of VCI is quite difficult due to the lack of both sensitive and specific biomarkers. Extensive damage to the white matter tracts, which connect the cortical and subcortical regions, has been shown in subcortical VCI (SVCI), the most common subtype of VCI that is caused by small vessel disease. Two specific MRI sequences, including diffusion tensor imaging (DTI) and functional MRI (fMRI), have emerged as useful tools for identifying subtle white matter changes and the intrinsic connectivity between distinct cortical regions. This review describes the advantages of these two modalities in SVCI research and the current DTI and fMRI findings on SVCI. Using DTI technique, a variety of studies found that white matter microstructural damages in the anterior and superior areas are more specific to SVCI. Similarly, functional brain abnormalities detected by fMRI have also been mainly shown in anterior brain areas in SVCI. The characteristic distribution of brain abnormalities in SVCI interrupts the prefrontal-subcortical loop that results in cognitive impairments in particular domains, which further confirms the ‘disconnection syndrome’ hypothesis. In addition, another MRI technique, arterial spin labelling (ASL), has been used to describe the disconnection patterns in a variety of conditions by measuring cerebral blood flow. The role of the ASL technique in SVCI research is also assessed. Finally, the review proposes the application of multimodality fusion in the investigation of SVCI pathogenesis.

Progressively Disrupted Brain Functional Connectivity Network in Subcortical Ischemic Vascular Cognitive Impairment Patients

Cognitive impairment caused by subcortical ischemic vascular disease (SIVD) has been elucidated by many neuroimaging studies. However, little is known regarding the changes in brain functional connectivity networks in relation to the severity of cognitive impairment in SIVD. In the present study, 20 subcortical ischemic vascular cognitive impairment no dementia patients (SIVCIND) and 20 dementia patients (SIVaD) were enrolled; additionally, 19 normal controls were recruited. Each participant underwent a resting-state functional MRI scan. Whole-brain functional networks were analyzed with graph theory and network-based statistics (NBS) to study the functional organization of networks and find alterations in functional connectivity among brain regions. After adjustments for age, gender, and duration of formal education, there were significant group differences for two network functional organization indices, global efficiency and local efficiency, which decreased (NC > SIVCIND > SIVaD) as cognitive impairment worsened. Between-group differences in functional connectivity (NBS corrected, p < 0.01) mainly involved the orbitofrontal, parietal, and temporal cortices, as well as the basal ganglia. The brain connectivity network was progressively disrupted as cognitive impairment worsened, with an increased number of decreased connections between brain regions. We also observed more reductions in nodal efficiency in the prefrontal and temporal cortices for SIVaD than for SIVCIND. These findings indicated a progressively disrupted pattern of the brain functional connectivity network with increased cognitive impairment and showed promise for the development of reliable biomarkers of network metric changes related to cognitive impairment caused by SIVD.

Presence of lacunar infarctions is associated with the spatial navigation impairment in patients with mild cognitive impairment: a DTI study

Lacunar cerebral infarction (LI) is one of risk factors of vascular dementia and correlates with progression of cognitive impairment including the executive functions. However, little is known on spatial navigation impairment and its underlying microstructural alteration of white matter in patients with LI and with or without mild cognitive impairment (MCI). Our aim was to investigate whether the spatial navigation impairment correlated with the white matter integrity in LI patients with MCI (LI-MCI). Thirty patients with LI were included in the study and were divided into LI-MCI (n=17) and non MCI (LI-Non MCI) groups (n=13) according neuropsychological tests.The microstructural integrity of white matter was assessed by calculating a fractional anisotropy (FA) and mean diffusivity (MD) from diffusion tensor imaging (DTI) scans. The spatial navigation accuracy, separately evaluated as egocentric and allocentric, was assessed by a computerized human analogue of the Morris Water Maze tests Amunet. LI-MCI performed worse than the CN and LI-NonMCI groups on egocentric and delayed spatial navigation subtests. LI-MCI patients have spatial navigation deficits. The microstructural abnormalities in diffuse brain regions, including hippocampus, uncinate fasciculus and other brain regions may contribute to the spatial navigation impairment in LI-MCI patients at follow-up.

Neurovascular dysfunction in dementia - human cellular models and molecular mechanisms

From the earliest stages of development, when cerebral angiogenesis and neurogenesis are entwined, to the end of life, the interplay between vascular and neural systems of the brain is critical in health and disease. Cerebral microvascular endothelial cells constitute the blood-brain barrier and in concert with pericytes or smooth muscle cells, glia and neurons, integrate into a functional neurovascular unit (NVU). This multicellular NVU maintains homoeostasis of the brain's microenvironment by restricting the entry of systemic pathogens and neurotoxins as well as meeting the metabolic demands of neural activity. Recent evidence of cerebral microvascular pathologies in vascular diseases and dementia, including Alzheimer's disease, has challenged the notion that vascular events are merely the consequence of neuronal pathology. This review focuses on molecular mechanisms of neurovascular dysfunction in dementia and outlines currently employed in vitro models to decode such mechanisms. Deciphering neurovascular crosstalk is likely to be more important in understanding the molecular mechanisms of disease than previously anticipated and may offer novel therapeutic opportunities for dementia and related conditions.

The Role of Cerebrovascular Disease in Amyloid Deposition

BACKGROUND

Some patients clinically diagnosed with subcortical vascular cognitive impairment (SVCI) have co-morbidity with AD pathology.

OBJECTIVE

We investigated topographical differences in amyloid burden between SVCI and Alzheimer's disease type cognitive impairment (ADCI) using [11C] Pittsburgh compound B (PiB) positron emission tomography (PET). The purpose of this study was to investigate the role of cerebrovascular disease (CVD) in amyloid deposition.

METHODS

We recruited 44 patients with SVCI and 44 patients with ADCI (amnestic mild cognitive impairment or Alzheimer's disease) with absent or minimal white matter hyperintensities, all with PiB-positive PET scans [PiB+]. As controls, we included 13 participants with normal cognition and PiB-negative scans. We divided the SVCI and ADCI patients into three groups according to global PiB retention ratio of SVCI, and then compared the tertiles in terms of the distribution of PiB retention using statistical parametric mapping analyses. Lobar to global PiB retention ratio and asymmetry indices were also compared between SVCI and ADCI groupsResults: Compared to PiB+ ADCI patients, PiB+ SVCI patients exhibited: 1) increased left-right asymmetry, and increased anterior-posterior difference; and 2) increased PiB retention in the parietal cortex, the occipital cortex and the precuneus-posterior cingulate cortex. In contrast, ADCI patients showed increased PiB retention in the striatum. When stratified by level of PiB retention, each group showed different characteristics.

CONCLUSION

Our results showed that the distribution of amyloid deposition differed between patients with PiB+ SVCI and ADCI. These suggest that CVD contribute to and alter the known progression pattern in amyloid deposition in Alzheimer's disease.

Frontal Assessment Battery as a Useful Tool to Differentiate Mild Cognitive Impairment due to Subcortical Ischemic Vascular Disease from Alzheimer Disease

BACKGROUND

Prominent executive dysfunction can differentiate vascular dementia from Alzheimer disease (AD). However, it is unclear whether the Frontal Assessment Battery (FAB) screening tool can differentiate subcortical ischemic vascular disease (SIVD) from AD at the pre-dementia stage. In addition, the neural correlates of FAB performance have yet to be clarified.

METHODS

Patients with mild cognitive impairment (MCI) due to SIVD (MCI-V), MCI due to AD (MCI-A), and demographically matched controls completed the Mini-Mental State Examination, Taiwanese FAB (TFAB), Category Fluency, and Chinese Version of the Verbal Learning Test, and underwent magnetic resonance imaging. White matter hyperintensities were rated according to the Scheltens scale.

RESULTS

TFAB total scale and its Orthographical Fluency subtest were the only measures that could differentiate MCI-V from MCI-A. Discriminative analysis showed that Orthographical Fluency scores successfully identified 73.2% of the cases with MCI-V, with 85.0% sensitivity. Orthographical Fluency scores were specifically associated with lesion load within frontal periventricular, frontal deep white matter, and basal ganglia regions.

CONCLUSION

The TFAB, and especially its 1-min Orthographical Fluency subtest, is a useful screening procedure to differentiate MCI due to SIVD from MCI due to AD. The discriminative ability is probably due to frontosubcortical white matter pathologies disproportionately involved in the two disease entities.

The effects of environmental enrichment on white matter pathology in a mouse model of chronic cerebral hypoperfusion

White matter (WM) disintegration is common in the older population and is associated with vascular cognitive impairment (VCI). This study explored the effects of environmental enrichment (EE) on pathological sequelae in a mouse model of chronic cerebral hypoperfusion induced by bilateral common carotid artery stenosis (BCAS). Male C57BL/6 J mice underwent BCAS or sham surgery. One-week after surgery, mice were exposed to three different degrees of EE; either standard housing conditions (std), limited 3 h exposure to EE per day (3 h) or full-time exposure to EE (full) for 12 weeks. At 13 weeks after surgery, cognitive testing was performed using a three-dimensional 9-arm radial maze. At 16 weeks after surgery, nesting ability was assessed in each mouse immediately before euthanasia. Brains retrieved after perfusion fixation were examined for WM pathology. BCAS caused WM changes, as demonstrated by corpus callosum atrophy and greater WM disintegrity. BCAS also caused impaired nesting ability and cognitive function. These pathological changes and working memory deficits were attenuated, more so by limited rather than full-time exposure to EE regime. Our results suggest that limited exposure to EE delays the onset of WM degeneration. Therefore, the implementation of even limited EE may be beneficial for patients diagnosed with VCI.

Update on Vascular Cognitive Impairment Associated with Subcortical Small-Vessel Disease

Subcortical small-vessel disease (SSVD) is a disorder well characterized from the clinical, imaging, and neuropathological viewpoints. SSVD is considered the most prevalent ischemic brain disorder, increasing in frequency with age. Vascular risk factors include hypertension, diabetes, hyperlipidemia, elevated homocysteine, and obstructive sleep apnea. Ischemic white matter lesions are the hallmark of SSVD; other pathological lesions include arteriolosclerosis, dilatation of perivascular spaces, venous collagenosis, cerebral amyloid angiopathy, microbleeds, microinfarcts, lacunes, and large infarcts. The pathogenesis of SSVD is incompletely understood but includes endothelial changes and blood-brain barrier alterations involving metalloproteinases, vascular endothelial growth factors, angiotensin II, mindin/spondin, and the mammalian target of rapamycin pathway. Metabolic and genetic conditions may also play a role but hitherto there are few conclusive studies. Clinical diagnosis of SSVD includes early executive dysfunction manifested by impaired capacity to use complex information, to formulate strategies, and to exercise self-control. In comparison with Alzheimer's disease (AD), patients with SSVD show less pronounced episodic memory deficits. Brain imaging has advanced substantially the diagnostic tools for SSVD. With the exception of cortical microinfarcts, all other lesions are well visualized with MRI. Diagnostic biomarkers that separate AD from SSVD include reduction of cerebrospinal fluid amyloid-β (Aβ)42 and of the ratio Aβ42/Aβ40 often with increased total tau levels. However, better markers of small-vessel function of intracerebral blood vessels are needed. The treatment of SSVD remains unsatisfactory other than control of vascular risk factors. There is an urgent need of finding targets to slow down and potentially halt the progression of this prevalent, but often unrecognized, disorder.

Does cerebral large-artery disease contribute to cognitive impairment?

Purpose

Although many patients with cerebral large-artery disease (CLAD) show impaired cognitive performance, the risk factors remain unclear in this population. The objective of this study was to evaluate cognitive impairment and its risk factors in patients with CLAD.

Methods

We recruited non-demented patients with CLAD from our hospital. CLAD was defined as occlusion or stenosis of over 50% in the carotid artery or middle cerebral artery. We collected patients' biographical data and vascular lesion and imaging data, including periventricular hyperintensity (PVH) and cerebral perfusion. The patients were divided into two groups: cognitive impairment-plus (CoI +) and normal (CoI −) groups, according to their Montreal Cognitive Assessment (MoCA) scores, with a cut-off value of 26. The factors associated with cognitive impairment were examined.

Result

Of the 176 patients with CLAD (mean age 70.2 ± 8.3, 40 female), 136 (77.2%) were classified as cognitively impaired. Multivariate analysis indicated that the CoI + group was associated with older age (odds ratio (OR): 1.09, P = 0.011), drinking habit (OR: 7.15, P = 0.003), increased PVH (OR: 3.46, P = 0.003), and decreased cerebral perfusion (OR: 0.897, P = 0.007). Analyses of the MoCA subscores indicated that attention, memory, and orientation were impaired in the CoI + group.

Conclusion

Impaired cognition was observed in some of the non-demented patients with CLAD. Older age, drinking habit, severe PVH and decreased cerebral perfusion contributed to their poor cognitive performance. Strict treatment of atherosclerosis and intervention for CLAD might be necessary to prevent cognitive decline in these patients.

The diagnosis of dementias: a practical tool not to miss rare causes

Dementia represents one of the most diffuse disorders of our Era. Alzheimer's disease is the principle cause of dementia worldwide. Metabolic, infectious, autoimmune, inflammatory, and genetic dementias represent a not negligible number of disorders, with increasing numbers in younger subjects. Due to the heterogeneity of patients and disorders, the diagnosis of dementia is challenging. In the present article, we propose a practical diagnostic approach following the two-step investigation procedure. The first step includes basic blood tests and brain neuroimaging, performed on all patients. After this first-line investigation, it is then possible to rule out metabolic causes of dementia and to identify three main subgroups in dementia: predominant gray matter atrophy, white matter disease, basal ganglia pathologies. The predominant gray matter atrophy subgroup includes neurodegenerative causes of dementia and some lysosomal storage disorders. The white matter subgroup indicates a comprehensive list of vascular dementia causes, mitochondrial diseases, and leukodystrophies. Whereas, the basal ganglia alterations are due to metal accumulation pathologies, such as iron, copper, or calcium. Each category has specific clinical hallmarks, accurately reported in the article, and requires specific second-line investigation. Thus, we indicate the distinct second diagnostic step of each disease. The proposed diagnostic flow-chart follows the clinical reasoning and helps clinicians through the differential diagnosis of dementia.

Transcranial Doppler of the middle cerebral artery indicates regional gray matter cerebral perfusion

OBJECTIVE

We determined if transcranial color-coded Doppler derived hemodynamics are associated with MRI-based cerebral blood flow (CBF) in regions clinically important to dementia in healthy middle-aged adults.

APPROACH

In 30 subjects (18m/12f; age  =  52  ±  1 years), blood flow velocity (BFV) and cerebrovascular conductance (CVC) were measured with transcranial color-coded Doppler (TCCD) at the middle cerebral artery (MCA) and cerebral blood flow (CBF) was assessed with arterial spin labeled perfusion MRI.

MAIN RESULTS

BFV and CVC were associated with hippocampus (r  =  0.58 and r  =  0.61, both p  <  0.01) and occipitoparietal (r  =  0.50 and r  =  0.58, both p  <  0.01) CBF. CVC was further associated with posterior cingulate CBF (r  =  0.58 p  <  0.01). Independent of age and sex, BFV and CVC were associated with hippocampus (r  =  0.59 and r  =  0.55, both p  <  0.003) and occipitoparietal (r  =  0.50 and r  =  0.57, both p  <  0.01) CBF. CVC was independently associated with posterior cingulate CBF (r  =  0.38, p  =  0.049).

SIGNIFICANCE

TCCD-measured BFV and CVC of the MCA are indicators of cerebral perfusion to clinically valuable brain regions in healthy middle-aged adults. TCCD may not be a good indicator of blood flow to cerebral white matter.

Cilostazol alleviates white matter degeneration caused by chronic cerebral hypoperfusion in mice: Implication of its mechanism from gene expression analysis

Cilostazol is known to alleviate white matter demyelination due to chronic cerebral hypoperfusion in rodent models, although their pharmacological mechanisms remain unclear. In this study, we investigated the protective effect of cilostazol in relation to gene expression profile. Bilateral common carotid artery stenosis (BCAS) mice were treated with oral administration of cilostazol or placebo starting from a week after the surgery. Demyelination of the cingulum was compared between the 2 groups 2, 6, and 10 weeks after initial drug administration. Also, to examine temporal gene expression change during demyelination, DNA microarray analysis was conducted using samples from the corpus callosum of 2nd and 6th week BCAS mice. For genes that showed more than 2-fold up-regulation, their increase was validated by qPCR. Finally, to determine the effect of cilostazol towards those genes, their expression in the corpus callosum of 6-week placebo-treated and cilostazol-treated BCAS mice was compared by qPCR. Amelioration of myelin loss was observed in cilostazol-treated group, showing significant difference with those observed in placebo group after 10-week treatment. Gene ontology analysis of the 17 up-regulated (FDR<0.01) genes showed that majority of the genes were related to cell development processes. Among the validated genes, expression of Btg2 was significantly promoted in the corpus callosum of BCAS mice by administration of cilostazol. Results of this study suggest that activation of Btg2 may be one of the key pharmacological effects of cilostazol towards the white matter during chronic ischemia.