Different cognitive profiles between mild cognitive impairment due to cerebral small vessel disease and mild cognitive impairment of Alzheimer's disease origin

The assessment of executive function abilities in healthy and neurodegenerative aging-A selective literature review

Numerous studies have examined executive function (EF) abilities in cognitively healthy older adults and those living with mild cognitive impairment (MCI) and Alzheimer's disease (AD). Currently, there are no standard accepted protocols for testing specific EFs; thus, researchers have used their preferred tool, which leads to variability in assessments of decline in a particular ability across studies. Therefore, there is a need for guidance as to the most sensitive tests for assessing EF decline. A search of the most current literature published between 2000 and 2022 on EF studies assessing cognitively healthy older adults and individuals living with MCI and AD was conducted using PubMed/Medline, PsycINFO, Embase, Web of Science, and Google Scholar. Emphasis was placed on the EF's dual-tasking, inhibition, shifting or switching, and working memory updating. Many tasks and their outcomes were reviewed. Of particular importance was the difference in outcomes for tasks applied to the same group of participants. These various EF assessment tools demonstrate differences in effectively identifying decline in EF ability due to the aging process and neurodegenerative conditions, such as MCI and AD. This review identifies various factors to consider in using particular EF tasks in particular populations, including task demand and stimuli factors, and also when comparing differing results across studies.

Systematic Review and Meta-Analyses of Word Production Abilities in Dysfunction of the Basal Ganglia: Stroke, Small Vessel Disease, Parkinson's Disease, and Huntington's Disease

Clinical populations with basal ganglia pathologies may present with language production impairments, which are often described in combination with comprehension measures or attributed to motor, memory, or processing-speed problems. In this systematic review and meta-analysis, we studied word production in four (vascular and non-vascular) pathologies of the basal ganglia: stroke affecting the basal ganglia, small vessel disease, Parkinson's disease, and Huntington's disease. We compared scores of these clinical populations with those of matched cognitively unimpaired adults on four well-established production tasks, namely picture naming, category fluency, letter fluency, and past-tense verb inflection. We conducted a systematic search in PubMed and PsycINFO with terms for basal ganglia structures, basal ganglia disorders and language production tasks. A total of 114 studies were included, containing results for one or more of the tasks of interest. For each pathology and task combination, effect sizes (Hedges' g) were extracted comparing patient versus control groups. For all four populations, performance was consistently worse than that of cognitively unimpaired adults across the four language production tasks (p-values < 0.010). Given that performance in picture naming and verb inflection across all pathologies was quantified in terms of accuracy, our results suggest that production impairments cannot be fully explained by motor or processing-speed deficits. Our review shows that while language production difficulties in these clinical populations are not negligible, more evidence is necessary to determine the exact mechanism that leads to these deficits and whether this mechanism is the same across different pathologies.

A 19-Year-Old Adolescent with Probable Alzheimer's Disease

Alzheimer's disease (AD) primarily affects older adults. In this report, we present the case of a 19-year-old male with gradual memory decline for 2 years and World Health Organization-University of California Los Angeles Auditory Verbal Learning Test (WHO-UCLA AVLT) results also showing memory impairment. Positron emission tomography-magnetic resonance imaging with 18F fluorodeoxyglucose revealed atrophy of the bilateral hippocampus and hypometabolism in the bilateral temporal lobe. Examination of the patient's cerebrospinal fluid showed an increased concentration of p-tau181 and a decreased amyloid-β 42/40 ratio. However, through whole-genome sequencing, no known gene mutations were identified. Considering the above, the patient was diagnosed with probable AD.

The clinical profile of cerebral small vessel disease: Toward an evidence-based identification of cognitive markers

There is no consensus on which test is more suited to outline the cognitive deficits of cerebral small vessel disease (cSVD) patients. We explored the ability of eight cognitive tests, selected in a previous systematic review as the most commonly used in this population, to differentiate among cSVD patients, controls, and other dementing conditions performing a meta-analysis of 86 studies. We found that cSVD patients performed worse than healthy controls in all tests while data on the comparison to neurodegenerative diseases were limited. We outlined a lack of data on these tests' accuracy on the diagnosis. Cognitive tests measuring processing speed were those mostly associated with neuroimaging cSVD markers. There is currently incomplete evidence that a single test could differentiate cSVD patients with cognitive decline from other dementing diseases. We make preliminary proposals on possible strategies to gain information about the clinical definition of cSVD that currently remains a neuroimaging-based one.

The mean diffusivity of forceps minor is useful to distinguish amnestic mild cognitive impairment from mild cognitive impairment caused by cerebral small vessel disease

Objectives

In recent years, the desire to make a more fine-grained identification on mild cognitive impairment (MCI) has become apparent, the etiological diagnosis of MCI in particular. Nevertheless, new methods for the etiological diagnosis of MCI are currently insufficient. The objective of this study was to establish discriminative measures for amnestic mild cognitive impairment (a-MCI) and MCI caused by cerebral small vessel disease (CSVD).

Materials and methods

In total, 20 normal controls (NCs), 33 a-MCI patients, and 25 CSVD-MCI patients performed comprehensive neuropsychological assessments concerning global cognitive function and five cognitive domains as well as magnetic resonance imaging scan with diffusion tensor imaging (DTI). Diffusion parameters including fractional anisotropy and mean diffusivity of 20 major white matter metrics were obtained by ROI-based analyses. The neuropsychological tests and diffusion measurements were compared and binary logistic regression was used to identify the best differential indicator for the two MCI subgroups. The discriminating power was calculated by receiver operating characteristic analysis.

Results

Amnestic mild cognitive impairment group showed significant impairment in memory and language function, while CSVD-MCI group revealed more deficits in multi-cognitive domains of memory, language, attention and executive function than controls. Compared to the a-MCI, CSVD-MCI was significantly dysfunctional in the executive function. The CSVD-MCI group had decreased fractional anisotropy and increased mean diffusivity values throughout widespread white matter areas. CSVD-MCI presented more severe damage in the anterior thalamic radiation, forceps major, forceps minor and right inferior longitudinal fasciculus compared with a-MCI group. No significant neuropsychological tests were found in the binary logistic regression model, yet the DTI markers showed a higher discriminative power than the neuropsychological tests. The Stroop test errors had moderate potential (AUC = 0.747; sensitivity = 76.0%; specificity = 63.6%; P = 0.001; 95% CI: 0.617–0.877), and the mean diffusivity value of forceps minor demonstrated the highest predictive power to discriminate each MCI subtype (AUC = 0.815; sensitivity = 88.0%; specificity = 72.7%; P &lt; 0.001; 95% CI: 0.698–0.932).

Conclusion

The mean diffusivity of forceps minor may serve as an optimal indicator to differentiate between a-MCI and CSVD-MCI.

BDNF Val66Met Moderates the Effects of Hypertension on Executive Functioning in Older Adults Diagnosed With aMCI

OBJECTIVE

To investigate whether the BDNF Val66Met polymorphism influences the associations of hypertension, executive functioning and processing speed in older adults diagnosed with amnestic Mild Cognitive Impairment (aMCI).

DESIGN

Secondary data analysis using moderation modeling.

SETTING

Veterans Affairs Hospital, Palo Alto, CA.

PARTICIPANTS

Sample included 108 community-dwelling volunteers (mean age 71.3 ± 9.2 years) diagnosed with aMCI.

MEASUREMENTS

Cognitive performance was evaluated from multiple baseline assessments (Trail Making Test; Stroop Color-Word Test; Symbol Digit Modality Test) and grouped into standardized composite scores representing executive function and processing speed domains. BDNF genotypes were determined from whole blood samples. Hypertension was assessed from resting blood pressures or by self-report.

RESULTS

Controlling for age, BDNF Val66Met moderated the effects of hypertension on executive functioning, but added no significant variance to processing speed scores. Specifically, hypertensive carriers of the BDNF Met allele performed significantly below the sample mean on tasks of executive functioning, and evidenced significantly lower scores when compared to Val-Val homozygotes and normotensive participants.

CONCLUSIONS

Results posit that the executive functioning of non-demented older adults may be susceptible to interactions between BDNF genotype and hypertension, and Val-Val homozygotes and normotensive older adults may be more resilient to these effects of cognitive change. Further research is needed to understand the underlying processes and to implement strategies that target modifiable risk factors and promote cognitive resilience.

Linear linking for related traits (LLRT): A novel method for the harmonization of cognitive domains with no or few common items

Harmonization means to make data comparable. Recent efforts to generate comparable data on cognitive performance of older adults from many different countries around the world have presented challenges for direct comparison. Neuropsychological instruments vary in many respects, including language, administration techniques and cultural differences, which all present important obstacles to assumptions regarding the presence of linking items. Item response theory (IRT) methods have been previously used to harmonize cross-national data on cognition, but these methods rely on linking items to establish the shared metric. We introduce an alternative approach for linking cognitive performance across two (or more) groups when the fielded assessments contain no items that can be reasonably considered linking items: Linear Linking for Related Traits (LLRT). We demonstrate this methodological approach in a sample from a single United States study split by educational attainment, and in two sets of cross-national comparisons (United States to England, and United States to India). All data were collected as part of the Harmonized Cognitive Assessment Protocol (HCAP) and are publicly available. Our method relies upon strong assumptions, and we offer suggestions for how the method can be extended to relax those assumptions in future work.

Sex Differences in Cerebral Small Vessel Disease: A Systematic Review and Meta-Analysis

Background: Cerebral small vessel disease (SVD) is a common cause of stroke, mild cognitive impairment, dementia and physical impairments. Differences in SVD incidence or severity between males and females are unknown. We assessed sex differences in SVD by assessing the male-to-female ratio (M:F) of recruited participants and incidence of SVD, risk factor presence, distribution, and severity of SVD features. Methods: We assessed four recent systematic reviews on SVD and performed a supplementary search of MEDLINE to identify studies reporting M:F ratio in covert, stroke, or cognitive SVD presentations (registered protocol: CRD42020193995). We meta-analyzed differences in sex ratios across time, countries, SVD severity and presentations, age and risk factors for SVD. Results: Amongst 123 relevant studies (n = 36,910 participants) including 53 community-based, 67 hospital-based and three mixed studies published between 1989 and 2020, more males were recruited in hospital-based than in community-based studies [M:F = 1.16 (0.70) vs. M:F = 0.79 (0.35), respectively; p < 0.001]. More males had moderate to severe SVD [M:F = 1.08 (0.81) vs. M:F = 0.82 (0.47) in healthy to mild SVD; p < 0.001], and stroke presentations where M:F was 1.67 (0.53). M:F did not differ for recent (2015-2020) vs. pre-2015 publications, by geographical region, or age. There were insufficient sex-stratified data to explore M:F and risk factors for SVD. Conclusions: Our results highlight differences in male-to-female ratios in SVD severity and amongst those presenting with stroke that have important clinical and translational implications. Future SVD research should report participant demographics, risk factors and outcomes separately for males and females. Systematic Review Registration: [PROSPERO], identifier [CRD42020193995].

Higher Total Cerebral Small Vessel Disease Burden Was Associated With Mild Cognitive Impairment and Overall Cognitive Dysfunction: A Propensity Score-Matched Case-Control Study

Background and Objective

The combination of neuroimaging and cognition characteristics may provide complementary information for early identification of mild cognitive impairment (MCI). This study aimed to establish the clinical relevance between cerebral small vessel disease (CSVD) burden and MCI and further explored the cognitive characteristics linked to CSVD applying a propensity score matching (PSM) approach.

Methods

The study was designed as a case–control study. All the subjects underwent the standard clinical assessments, neuropsychological testing battery (including global cognition, memory, executive function, and speed and motor control domains), and brain magnetic resonance imaging (MRI). A 1:2 nearest-neighbor matching approach without replacement was employed with a caliper of 0.15 in the PSM approach.

Results

A total of 84 MCI patients and 186 cognitively normal controls were included in this study. After PSM, 74 MCI patients and 129 controls were successfully matched, and the covariate imbalance was well eliminated. Compared with controls, the MCI group had more severe CSVD burden. In the binary logistic regression analysis, CSVD was associated with MCI after adjusting for all confounders. The results of multivariate linear regression analyses showed that higher total MRI CSVD burden was related to the deficit of cognitive performance in global cognition and three important cognitive domains after adjusting for all confounders.

Conclusion

Cerebral small vessel disease was an independent risk factor of MCI. Moreover, higher total MRI CSVD burden was associated with the overall cognitive impairment among middle-aged and elderly Chinese adults.

Cognitive impairment in sporadic cerebral small vessel disease: A systematic review and meta-analysis

This paper is a proposal for an update on the characterization of cognitive impairments associated with sporadic cerebral small vessel disease (SVD). We pose a series of questions about the nature of SVD-related cognitive impairments and provide answers based on a comprehensive review and meta-analysis of published data from 69 studies. Although SVD is thought primarily to affect executive function and processing speed, we hypothesize that SVD affects all major domains of cognitive ability. We also identify low levels of education as a potentially modifiable risk factor for SVD-related cognitive impairment. Therefore, we propose the use of comprehensive cognitive assessments and the measurement of educational level both in clinics and research settings, and suggest several recommendations for future research.

A Virtual Reality-Based Screening Test for Cognitive Impairment in Small Vessel Disease

Background:

There is a need for new practical tools to assess the cognitive impairment of small vessel disease (SVD) patients in the clinic.

Objective:

This study aimed to examine cognitive functioning by administering the Virtual Supermarket (VST) in patients with SVD with cognitive impairment (SVD-CI, N = 32), cognitively normal SVD (SVD-CN, N = 37), and age-and education-matched healthy controls (HC, N = 30).

Methods:

The tablet-based VST application and comprehensive traditional pencil-and-paper neuropsychological tests assessing memory, attention, executive function, visuospatial function, and language were administered to all participants.

Results:

A moderate correlation was found between the “Duration” and “Correct Quantities” variables of VST and visuospatial function and general cognitive status composite Z scores across SVD-CI patients. “Duration” and “Correct Money” variables were moderately related to memory, executive functions, and visuospatial function composite Z scores across SVD-CN patients. A combination of all VST variables discriminated SVD-CI and HC with a correct classification rate of 81%, a sensitivity of 78%, and a specificity of 84%.

Conclusion:

This study is the first to evaluate cognitive functions employing the VST in SVD with and without cognitive impairment. It provides encouraging preliminary findings of the utility of the VST as a screening tool in the assessment of cognitive impairment and the differentiation of SVD patients from HC. In the future, validation studies of the VST with larger samples are needed.

Structural Brain Network Disruption at Preclinical Stage of Cognitive Impairment Due to Cerebral Small Vessel Disease

Cerebral small vessel disease (CSVD) is a common disease among elderly individuals and recognized as a major cause of vascular cognitive impairment. Recent studies demonstrated that CSVD is a disconnection syndrome. However, due to the covert neurological symptoms and subtle changes in clinical performance, the connection alterations during the stage of preclinical cognitive impairment (PCI) and mild cognitive impairment (MCI) are usually neglected and still largely unknown. Using diffusion tensor imaging (DTI), we investigated the early structural network changes in PCI and MCI patients. The PCI group demonstrated well preserved rich-club organization, less nodal strength loss, and disruption of connections centered in the feeder and local connections. Nevertheless, the MCI group manifested a disruption in the rich-club organization, a worse nodal strength loss especially in hub nodes, and an overall disturbance in rich-club, feeder and local connections. Moreover, in all CSVD patients, the strength of the rich-club, feeder and local connections was significantly correlated with multiple cognitive scores, especially in attention, executive, and memory domains; while in MCI patients, only the strength of the rich-club connections was significantly correlated with cognition. Furthermore, based on the network-based statistic analysis, we also identified distinct network component disruption pattern between the PCI group and the MCI group, validating the results described above. These results suggest a disruption pattern from peripheral to central connections with the change of cognitive status, shedding light on the early identification and the underlying disruption of CSVD.

Effectiveness of sorting tests for detecting cognitive decline in older adults with dementia and other common neurodegenerative disorders: A meta-analysis

The demand for simple, accurate and time-efficient screens to detect cognitive decline at point-of-care is increasing. Sorting tests are often used to detect the 'executive' deficits that are commonly associated with behavioural-variant frontotemporal dementia (bvFTD), but their potential for use as a cognitive screen with older adults is unclear. A comprehensive search of four databases identified 142 studies that compared the sorting test performance (e.g. WCST, DKEFS-ST) of adults with a common neurodegenerative disorder (e.g. Alzheimer's disease, vascular dementia, bvFTD, Parkinson's disease) and cognitively-healthy controls. Hedges' g effect sizes were used to compare the groups on five common test scores (Category, Total, Perseveration, Error, Description). The neurodegenerative disorders (combined) showed large deficits on all scores (g -1.0 to -1.3), with dementia (combined subtypes) performing more poorly (g -1.2 to -2.1), although bvFTD was not disproportionately worse than the other dementias. Overall, sorting tests detected the cognitive impairments caused by common neurodegenerative disorders, especially dementia, highlighting their potential suitability as a cognitive screen for older adults.

How does white matter microstructure differ between the vascular and amnestic mild cognitive impairment?

Changes in white matter (WM) microstructure may relate to the pathophysiology of cognitive impairment. Whether WM microstructure differs in two common pre-dementia subtypes, vascular mild cognitive impairment (VaMCI) and amnestic mild cognitive impairment (aMCI), is largely unknown. This study included 28 VaMCI (12 men, age: 46 ~ 77 years) and 34 aMCI patients (14 men, age: 51 ~ 79 years). All patients underwent a battery of neuropsychological tests and structural and diffusion magnetic resonance imaging (MRI) scanning. WM microstructure was quantified using diffusion MRI parameters: fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AxD) and radial diffusivity (RD). These parameters were compared between the two patient groups using tract-based spatial statistics (TBSS) after controlling for age, gender, and education. No significant differences in FA/MD/AxD/RD were observed between the VaMCI and aMCI groups, which suggests a similar pattern of WM microstructure in the early stage of cognitive impairment for different dementia types. However, the two groups exhibited significant differences in the relationship between FA and the Auditory Verbal Learning Test (AVLT), which were primarily located around the corona radiate and corpus callosum. Specifically, there were significant positive correlations (R = 0.64, P < 0.001) between the FA and AVLT in the VaMCI group, but the opposite trend was observed in the aMCI group (R = -0.34, P = 0.047). The differential relationship between WM and memory between VaMCI and aMCI indicates an independent neuropathology for specific memory deficits in different types of dementia.

The Brief Memory and Executive Test (BMET): A cognitive screening tool to detect and differentiate vascular cognitive impairment and Alzheimer's disease

OBJECTIVE

While there are several cognitive screening tests available for the detection of cortical dementias such as Alzheimer's disease (AD), these are rarely designed to be sensitive to vascular cognitive impairment (VCI). The Brief Memory and Executive Test (BMET) is a screening measure designed to be sensitive to the cognitive profile of both VCI and AD. This study investigated the ability of the BMET to detect AD, and to differentiate between VCI and AD.

METHODS

This study included 150 patients, with either SVD, both with (n = 48) and without VCI (n = 51), or AD (N = 51) and 51 healthy controls. Participants were aged between 40 and 90 years of age and completed both the BMET and the MMSE.

RESULTS

Receiver operator characteristic (ROC) curve analysis showed as before the BMET is a good predictor SVD. Additionally, the BMET was a good predictor of AD (AUC = 0.96) and performed at least as well as the MMSE (AUC = 0.92) when differentiating AD patients from healthy controls. The BMET had a sensitivity of 86% and specificity of 100% for detecting AD patients from control subjects. Using the difference in cognitive profile between the AD and VCI group, we developed an index score which correctly classified 76% of patients as either having VCI or AD.

CONCLUSION

The BMET is a brief and sensitive tool for the detection of cognitive impairment due to both SVD and AD and can be used to aid in the differentiation of the 2 diseases.

Identification of key signaling pathways in cerebral small vessel disease using differential pathway network analysis

Cerebral small vessel disease (CSVD) primarily affects the perforating cerebral arterioles and capillaries, and results in injury to subcortical grey and white matter. Despite advances in determining the genetic basis of CSVD, the molecular mechanisms underlying the development and progression of CSVD remain unclear. The present study aimed to identify significant signaling pathways associated with CSVD based on differential pathway network analysis. Combining CSVD microarray data with human protein-protein interaction data and data from the Reactome pathway database, pathway interactions were constructed using the Spearman's correlation coefficient strategy. Pathway interactions with weight values of >0.95 were selected to construct the differential pathway network, which contained 715 differential pathway interactions covering 312 nodes and was visualized using Cytoscape software. A total of 15 hub pathways with a top 5% degree distribution in the differential pathway network were identified. The top 5 hub pathways were associated with the synthesis and metabolism of fatty acids. The results of the present study indicate that the synthesis and metabolism of fatty acids is associated with the occurrence and development of CSVD, and may thus provide insights to improve the early diagnosis and treatment of CSVD.

Diffusion tensor image segmentation of the cerebrum provides a single measure of cerebral small vessel disease severity related to cognitive change

Cerebral small vessel disease (SVD) is the primary cause of vascular cognitive impairment and is associated with decline in executive function (EF) and information processing speed (IPS). Imaging biomarkers are needed that can monitor and identify individuals at risk of severe cognitive decline. Recently there has been interest in combining several magnetic resonance imaging (MRI) markers of SVD into a unitary score to describe disease severity. Here we apply a diffusion tensor image (DTI) segmentation technique (DSEG) to describe SVD related changes in a single unitary score across the whole cerebrum, to investigate its relationship with cognitive change over a three-year period. 98 patients (aged 43-89) with SVD underwent annual MRI scanning and cognitive testing for up to three years. DSEG provides a vector of 16 discrete segments describing brain microstructure of healthy and/or damaged tissue. By calculating the scalar product of each DSEG vector in reference to that of a healthy ageing control we generate an angular measure (DSEG θ) describing the patients' brain tissue microstructural similarity to a disease free model of a healthy ageing brain. Conventional MRI markers of SVD brain change were also assessed including white matter hyperintensities, cerebral atrophy, incident lacunes, cerebral-microbleeds, and white matter microstructural damage measured by DTI histogram parameters. The impact of brain change on cognition was explored using linear mixed-effects models. Post-hoc sample size analysis was used to assess the viability of DSEG θ as a tool for clinical trials. Changes in brain structure described by DSEG θ were related to change in EF and IPS (p < 0.001) and remained significant in multivariate models including other MRI markers of SVD as well as age, gender and premorbid IQ. Of the conventional markers, presence of new lacunes was the only marker to remain a significant predictor of change in EF and IPS in the multivariate models (p = 0.002). Change in DSEG θ was also related to change in all other MRI markers (p < 0.017), suggesting it may be used as a surrogate marker of SVD damage across the cerebrum. Sample size estimates indicated that fewer patients would be required to detect treatment effects using DSEG θ compared to conventional MRI and DTI markers of SVD severity. DSEG θ is a powerful tool for characterising subtle brain change in SVD that has a negative impact on cognition and remains a significant predictor of cognitive change when other MRI markers of brain change are accounted for. DSEG provides an automatic segmentation of the whole cerebrum that is sensitive to a range of SVD related structural changes and successfully predicts cognitive change. Power analysis shows DSEG θ has potential as a monitoring tool in clinical trials. As such it may provide a marker of SVD severity from a single imaging modality (i.e. DTIs).

Diagnostic Values of Serum Levels of Homocysteine and Uric Acid for Predicting Vascular Mild Cognitive Impairment in Patients with Cerebral Small Vessel Disease

Background

This study aimed to investigate the diagnostic values of serum levels of Hcy and UA for predicting vascular mild cognitive impairment (VMCI) in patients with cerebral small vessel disease (SVD).

Material/Method

We selected 172 cerebral SVD patients and divided them into a VMCI group and a non-VMCI group. Eighty-six healthy individuals without nervous system diseases were selected as the control group. Enzymatic cycling method was performed to detect serum Hcy and UA levels. Serum levels of folic acid (FOA) and vitamin B12 (VitB12) were detected by chemiluminescence immunoassay. Montreal cognitive assessment (MoCA) was applied to evaluate the cognitive function. The ROC curve was used to evaluate the diagnostic values of serum Hcy and UA levels for predicting VMCI. Logistic regression analysis was used to determine the possible risk factors.

Results

Compared with the non-VMCI and control groups, serum FOA and VitB12 levels were lower and serum Hcy and UA levels were higher in the VMCI group. AUC values of serum Hcy and UA levels were 0.703 and 0.829, respectively. Serum Hcy and UA levels were negatively correlated with serum FOA and VitB12 levels, total MoCA score, and subscores on visuospatial ability and executive function, on language ability and on delayed recall, and they were positively correlated with serum cholesterol (CH) level. Serum Hcy and UA levels were indicated as risk factors for VMCI in cerebral SVD patients.

Conclusions

These results suggest that serum Hcy and UA levels may serve as predictive factors for VMCI in cerebral SVD patients.

MRI-based comparative study of different mild cognitive impairment subtypes: protocol for an observational case-control study

INTRODUCTION

Amnestic mild cognitive impairment (aMCI) and vascular mild cognitive impairment (VaMCI) comprise the 2 main types of mild cognitive impairment (MCI). The first condition generally progresses to Alzheimer's disease, whereas the second is likely to develop into vascular dementia (VD). The brain structure and function of patients with MCI differ from those of normal elderly individuals. However, whether brain structures or functions differ between these 2 MCI subtypes has not been studied. This study is designed to analyse neuroimages of brain in patients with VaMCI and aMCI using multimodality MRI (structural MRI (sMRI), functional MRI and diffusion tensor imaging (DTI)).

METHODS AND ANALYSIS

In this study, 80 participants diagnosed with aMCI, 80 participants diagnosed with VaMCI, and 80 age-matched, gender-matched and education-matched normal controls (NCs) will be recruited to the Hongqi Hospital of Mudanjiang Medical University, Heilongjiang, China. All participants will undergo neuroimaging and neuropsychological evaluations. The primary outcome measures will be (1) microstructural alterations revealed by multimodal MRIs, including sMRI, resting-state functional MRI and DTI; and (2) a neuropsychological evaluation, including the Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), Auditory Verbal Learning Test (AVLT), Memory and Executive Screening (MES), trail making test, Stroop colour naming condition and Clinical Dementia Rating (CDR) scale, to evaluate global cognition, memory function, attention, visuospatial skills, processing speed, executive function and emotion, respectively.

TRIAL REGISTRATION NUMBER

NCT02706210; Pre-results.

Neuropsychological characteristics of encephalopathy in Susac's Syndrome - Case report

Susac's Syndrome (SS) is a rare, autoimmune angiopathy characterized by hearing loss, retinal artery occlusions and encephalopathy, which is usually expressed in multifocal neurological signs and symptoms, confusion state and cognitive impairment. There have been few descriptions of neuropsychological assessment of SS. We present a case study of 29-year-old woman who developed full SS. During the post-acute stage of disease, she was admitted to neurorehabilitation ward to improve her cognitive-behavioral and motor functioning. The initial assessment revealed attention, memory and executive dysfunctions, as well as behavioral changes including impulsivity, affective dysregulation and reduced self-awareness of disease deficits. After five weeks recovery process supported by rehabilitation program, improvement was observed, although some cognitive-behavioral deficits were still present in the follow-up assessment.

Disruption of rich club organisation in cerebral small vessel disease

Cerebral small vessel disease (SVD) is an important cause of vascular cognitive impairment. Recent studies have demonstrated that structural connectivity of brain networks in SVD is disrupted. However, little is known about the extent and location of the reduced connectivity in SVD. Here they investigate the rich club organisation-a set of highly connected and interconnected regions-and investigate whether there is preferential rich club disruption in SVD. Diffusion tensor imaging (DTI) and cognitive assessment were performed in a discovery sample of SVD patients (n = 115) and healthy control subjects (n = 50). Results were replicated in an independent dataset (49 SVD with confluent WMH cases and 108 SVD controls) with SVD patients having a similar SVD phenotype to that of the discovery cases. Rich club organisation was examined in structural networks derived from DTI followed by deterministic tractography. Structural networks in SVD patients were less dense with lower network strength and efficiency. Reduced connectivity was found in SVD, which was preferentially located in the connectivity between the rich club nodes rather than in the feeder and peripheral connections, a finding confirmed in both datasets. In discovery dataset, lower rich club connectivity was associated with lower scores on psychomotor speed (β = 0.29, P < 0.001) and executive functions (β = 0.20, P = 0.009). These results suggest that SVD is characterized by abnormal connectivity between rich club hubs in SVD and provide evidence that abnormal rich club organisation might contribute to the development of cognitive impairment in SVD. Hum Brain Mapp 38:1751-1766, 2017. © 2017 Wiley Periodicals, Inc.

Neuroimaging criteria and cognitive performance in vascular mild cognitive impairment: A systematic review

The recognition of Cerebrovascular Disease (CVD) at earlier clinical stages may favor the control of vascular risk factors and prevention of dementia. However, operational criteria for symptomatic phases at non-dementia stages are often difficult, as the current criteria normally require the evidence of extensive subcortical disease.

Pattern and Rate of Cognitive Decline in Cerebral Small Vessel Disease: A Prospective Study

Objectives

Cognitive impairment, predominantly affecting processing speed and executive function, is an important consequence of cerebral small vessel disease (SVD). To date, few longitudinal studies of cognition in SVD have been conducted. We determined the pattern and rate of cognitive decline in SVD and used the results to determine sample size calculations for clinical trials of interventions reducing cognitive decline.

Methods

121 patients with MRI confirmed lacunar stroke and leukoaraiosis were enrolled into the prospective St George’s Cognition And Neuroimaging in Stroke (SCANS) study. Patients attended one baseline and three annual cognitive assessments providing 36 month follow-up data. Neuropsychological assessment comprised a battery of tests assessing working memory, long-term (episodic) memory, processing speed and executive function. We calculated annualized change in cognition for the 98 patients who completed at least two time-points.

Results

Task performance was heterogeneous, but significant cognitive decline was found for the executive function index (p<0.007). Working memory and processing speed decreased numerically, but not significantly. The executive function composite score would require the smallest samples sizes for a treatment trial with an aim of halting decline, but this would still require over 2,000 patients per arm to detect a 30% difference with power of 0.8 over a three year follow-up.

Conclusions

The pattern of cognitive decline seen in SVD over three years is consistent with the pattern of impairments at baseline. Rates of decline were slow and sample sizes would need to be large for clinical trials aimed at halting decline beyond initial diagnosis using cognitive scores as an outcome measure. This emphasizes the importance of more sensitive surrogate markers in this disease.

Association of sleep disordered breathing and cognitive deficit in APOE ε4 carriers

STUDY OBJECTIVES

The aim of the study was to determine whether apolipoprotein E epsilon 4 genotype (APOE4) modifies the association of sleep disordered breathing (SDB) with cognitive function in a middle-aged population.

DESIGN

Cross-sectional analysis of a community-dwelling cohort.

SETTINGS

Sleep laboratory at the Clinical Research Unit of the University of Wisconsin Hospitals and Clinics.

PARTICIPANTS

There were 755 adults from the Wisconsin Sleep Cohort who provided a total of 1,843 polysomnography and cognitive evaluations (most participants were assessed multiple times at approximately 4-y intervals); 56% males, average age 53.9 years (range 30-81 years).

INTERVENTIONS

None.

MEASUREMENT AND RESULTS

In-laboratory overnight polysomnography was used to assess SDB. Cognition was evaluated by a battery of six neurocognitive tests assessing memory and learning, attention, executive function, and psychomotor efficiency. The APOE4 genotype (ε3/ε4 or ε4/ ε4) was identified in 200 participants. Data were analyzed using linear mixed-effects models, accounting for multiple observations per participant. Cognitive test scores were regressed on SDB categories (AHI < 5, 5 ≤ AHI < 15, AHI ≥ 15); APOE4 and their interaction; and age, education, sex, and body mass index. There was no statistically significant association between SDB and cognitive performance among APOE4-negative individuals. However, in APOE4-positive individuals, those with AHI ≥ 15 had significantly worse performance on the Auditory Verbal Learning Test and the Controlled Oral Word Association Test.

CONCLUSIONS

In APOE4-positive individuals, moderate to severe sleep disordered breathing (AHI ≥ 15) was associated with poorer performance on cognitive tests that require both memory and executive function engagement.

Mechanisms of cognitive impairment in cerebral small vessel disease: multimodal MRI results from the St George's cognition and neuroimaging in stroke (SCANS) study

Cerebral small vessel disease (SVD) is a common cause of vascular cognitive impairment. A number of disease features can be assessed on MRI including lacunar infarcts, T2 lesion volume, brain atrophy, and cerebral microbleeds. In addition, diffusion tensor imaging (DTI) is sensitive to disruption of white matter ultrastructure, and recently it has been suggested that additional information on the pattern of damage may be obtained from axial diffusivity, a proposed marker of axonal damage, and radial diffusivity, an indicator of demyelination. We determined the contribution of these whole brain MRI markers to cognitive impairment in SVD. Consecutive patients with lacunar stroke and confluent leukoaraiosis were recruited into the ongoing SCANS study of cognitive impairment in SVD (n = 115), and underwent neuropsychological assessment and multimodal MRI. SVD subjects displayed poor performance on tests of executive function and processing speed. In the SVD group brain volume was lower, white matter hyperintensity volume higher and all diffusion characteristics differed significantly from control subjects (n = 50). On multi-predictor analysis independent predictors of executive function in SVD were lacunar infarct count and diffusivity of normal appearing white matter on DTI. Independent predictors of processing speed were lacunar infarct count and brain atrophy. Radial diffusivity was a stronger DTI predictor than axial diffusivity, suggesting ischaemic demyelination, seen neuropathologically in SVD, may be an important predictor of cognitive impairment in SVD. Our study provides information on the mechanism of cognitive impairment in SVD.

Relationship between cortical microinfarcts and cognitive impairment in Alzheimer's disease

Cerebrovascular disease and AD pathology co-exist in most dementia cases, and microinfarcts (MIs), particularly if cortical and multiple, play an additive and independent role in AD cognitive impairment. The main cause of cortical MIs is chronic cerebral hypoperfusion but occlusive vascular diseases, embolism and blood-brain barrier disruptions, isolated or combined, may also play a role. The precise mechanisms by which MIs cause cognitive impairment are not well known, but one plausible explanation is that they are widespread and accompanied by diffuse hypoperfusion, hypoxia, oxidative stress and inflammation, particularly in the watershed areas of the tertiary association cortex, and hence could damage cognition networks and explain many of AD's cognitive and behavioral disturbances. Therefore, it is crucial to control vascular risk factors and avoid uncontrolled use of the antihypertensives, neuroleptics and other sedative drugs frequently prescribed to AD patients.

Dysexecutive syndrome and cerebrovascular disease in non-amnestic mild cognitive impairment: A systematic review of the literature

Objective

Non-amnestic dysexecutive Vascular Mild Cognitive Impairment (VaMCI) may represent preclinical Vascular Dementia (VaD). The aim of this study was to summarize the clinical, neuropsychological and neuroimaging aspects of VaMCI; and to assess its patterns of progression to dementia.

Methods

Searches were made in the ISI Web of Knowledge, PubMed and Lilacs databases, using the terms "mild cognitive impairment" and "executive function". Altogether, 944 articles were retrieved.

Results

VaMCI cases had poorer performances on fronto-executive tasks, a higher prevalence of stroke, presence of periventricular and profound white matter hyperintensities on MRI images, as well as more extrapyramidal signs and behavioral symptoms. Executive dysfunction might be associated with disconnection of fronto-parietal-subcortical circuits. Progression to dementia was associated with baseline deficits in executive function, in simple sustained attention and language, and large periventricular WMH.

Discussion

VaMCI develops with impairment in non-memory domains and subcortical white matter changes on MRI images, which are consistent with clinical and neuroimaging findings in VaD.

Diagnosis of vascular cognitive impairment and its main categories

OBJECTIVE

A review of current criteria for the diagnosis of categories related with vascular cognitive impairment, in particular the nomenclature, diagnostic criteria, and differential clinical-radiological findings.

DEVELOPMENT

The criteria for the diagnosis of vascular cognitive impairment have evolved, but available criteria were designed basically for differentiating between vascular dementia and dementia due to Alzheimer disease, and for research purposes. Nevertheless, in clinical practice precise elements are required for: 1) Clinical diagnosis of dementia and mild cognitive impairment; 2) Clinical and neuroimaging criteria for identification of the various cerebrovascular lesions associated with cognitive dysfunction, and 3) A formulation of the aetiogenic-pathogenic relationship between cognitive impairment and cerebrovascular lesions. For this reason, a review was carried out on the diagnostic elements of vascular cognitive impairment categories, classification, and their most relevant characteristics. It highlights the characteristic for the diagnosis of multi-infarction dementia, strategic single infarct dementia, small vessel disease with dementia, mixed dementia, and vascular mild cognitive impairment.

CONCLUSIONS

Standardisation is required, by a multidisciplinary expert team, as regards nomenclature and criteria for the diagnosis of the full spectrum associated with vascular cognitive impairment and especially for vascular dementia and its categories.

The profile of executive functioning in amnestic mild cognitive impairment: disproportionate deficits in inhibitory control

Amnestic mild cognitive impairment (aMCI) represents a group of individuals who are highly likely to develop Alzheimer's disease (AD). Although aMCI is typically conceptualized as involving predominantly deficits in episodic memory, recent studies have demonstrated that deficits in executive functioning may also be present, and thorough categorization of cognitive functioning in MCI may improve early diagnosis and treatment of AD. We first provide an extensive review of neuropsychology studies that examined executive functioning in MCI. We then present data on executive functioning across multiple sub-domains (divided attention, working memory, inhibitory control, verbal fluency, and planning) in 40 aMCI patients (single or multiple domain) and 32 normal elderly controls (NECs). MCI patients performed significantly worse than NECs in all 5 sub-domains, and there was impairment (>1.0 SD below the mean of NECs) in all sub-domains. Impairment on each test was frequent, with 100% of MCI patients exhibiting a deficit in at least one sub-domain of executive functioning. Inhibitory control was the most frequently and severely impaired. These results indicate that executive dysfunction in multiple sub-domains is common in aMCI and highlights the importance of a comprehensive neuropsychological evaluation for fully characterizing the nature and extent of cognitive deficits in MCI.

Cerebral small vessel disease: cognition, mood, daily functioning, and imaging findings from a small pilot sample

Cerebral small vessel disease, a leading cause of cognitive decline, is considered a relatively homogeneous disease process, and it can co-occur with Alzheimer's disease. Clinical reports of magnetic resonance imaging (MRI)/computed tomography and single photon emission computed tomography (SPECT) imaging and neuropsychology testing for a small pilot sample of 14 patients are presented to illustrate disease characteristics through findings from structural and functional imaging and cognitive assessment. Participants showed some decreases in executive functioning, attention, processing speed, and memory retrieval, consistent with previous literature. An older subgroup showed lower age-corrected scores at a single time point compared to younger participants. Performance on a computer-administered cognitive measure showed a slight overall decline over a period of 8–28 months. For a case study with mild neuropsychology findings, the MRI report was normal while the SPECT report identified perfusion abnormalities. Future research can test whether advances in imaging analysis allow for identification of cerebral small vessel disease before changes are detected in cognition.