Neuropsychological and neuroimaging markers in prediction of cognitive impairment after ischemic stroke: a prospective follow-up study

Network analysis of neuropsychiatric, cognitive, and functional complications of stroke: implications for novel treatment targets

AIM

Recovery from stroke is adversely affected by neuropsychiatric complications, cognitive impairment, and functional disability. Better knowledge of their mutual relationships is required to inform effective interventions. Network theory enables the conceptualization of symptoms and impairments as dynamic and mutually interacting systems. We aimed to identify interactions of poststroke complications using network analysis in diverse stroke samples.

METHODS

Data from 2185 patients were sourced from member studies of STROKOG (Stroke and Cognition Consortium), an international collaboration of stroke studies. Networks were generated for each cohort, whereby nodes represented neuropsychiatric symptoms, cognitive deficits, and disabilities on activities of daily living. Edges characterized associations between them. Centrality measures were used to identify hub items.

RESULTS

Across cohorts, a single network of interrelated poststroke complications emerged. Networks exhibited dissociable depression, apathy, fatigue, cognitive impairment, and functional disability modules. Worry was the most central symptom across cohorts, irrespective of the depression scale used. Items relating to activities of daily living were also highly central nodes. Follow-up analysis in two studies revealed that individuals who worried had more densely connected networks than those free of worry (CASPER [Cognition and Affect after Stroke: Prospective Evaluation of Risks] study: S = 9.72, P = 0.038; SSS [Sydney Stroke Study]: S = 13.56, P = 0.069).

CONCLUSION

Neuropsychiatric symptoms are highly interconnected with cognitive deficits and functional disabilities resulting from stroke. Given their central position and high level of connectedness, worry and activities of daily living have the potential to drive multimorbidity and mutual reinforcement between domains of poststroke complications. Targeting these factors early after stroke may have benefits that extend to other complications, leading to better stroke outcomes.

Absence in CX3CR1 receptor signaling promotes post-ischemic stroke cognitive function recovery through suppressed microglial pyroptosis in mice

BACKGROUND

Post-stroke cognitive impairment (PSCI) is a major source of morbidity and mortality after stroke, but the pathological mechanisms remain unclear. Previous studies have demonstrated that the CX3CR1 receptor plays a crucial role in maintaining an early protective microenvironment after stroke, but whether it persistently influences cognitive dysfunction in the chronic phase requires further investigation.

METHODS

Mouse was used to establish a middle cerebral artery occlusion (MCAO)/reperfusion model to study PSCI. Cognitive function was assessed by the Morris water maze (MWM) and the novel object recognition test. Neurogenesis was assessed by immunofluorescence staining with Nestin+ /Ki67+ and DCX+ /BrdU+ double-positive cells. The cerebral damage was monitored by [18 F]-DPA-714 positron emission tomography, Nissel, and TTC staining. The pyroptosis was histologically, biochemically, and electron microscopically examined.

RESULTS

Upon MCAO, at 28 to 35 days, CX3CR1 knockout (CX3CR1-/- ) mice had better cognitive behavioral performance both in MWM and novel object recognition test than their CX3CR1+/- counterparts. Upon MCAO, at 7 days, CX3CR1-/- mice increased the numbers of Nestin+ /Ki67+ and DCX+ /BrdU+ cells, and meanwhile it decreased the protein expression of GSDMD, NLRP3 inflammasome subunit, caspase-1, mature IL-1β/IL-18, and p-P65 in the hippocampus as compared with CX3CR1+/- mice. In addition, CX3CR1-/- mice could reverse infarct volume in the hippocampus region post-stroke.

CONCLUSION

Our study demonstrated that CX3CR1 gene deletion was beneficial to PSCI recovery. The mechanism might lie in inhibited pyroptosis and enhanced neurogenesis. CX3CR1 receptor may serve as a therapeutic target for improving the PSCI.

Neuropsychological Assessment of Community-Dwelling Older Adults in Almaty, Kazakhstan

Cognitive impairment in older adults is a major public concern for Kazakhstan's aging population. We aimed to (1) administer a neuropsychological test battery (NTB) in domains relevant to aging-associated cognitive impairment in a sample of adults aged 60+ without dementia in Almaty, Kazakhstan; (2) investigate the associations between demographic factors and test performance; and (3) provide information on the distribution of NTB scores as preliminary local normative data relevant for this population. A cross-sectional evaluation of 276 participants aged 60+ in Almaty, Kazakhstan, was conducted using cognitive instruments including tests of memory, attention, language, executive functions, visuospatial abilities, and processing speed. Multiple linear regression analyses were used to examine the association of demographic factors with neuropsychological test performance. The results from the regression analysis showed that those who are younger, have more years of education, are women, and are of Russian ethnicity had significantly better performance. The current study illustrated (1) the feasibility of administering the NTB to older adults in the general population in Kazakhstan; (2) the preliminary local normative neuropsychological measures; and (3) their independent associations with age, education, gender, and ethnicity. The findings are a platform for future research on dementia and cognitive impairment in older adults in Kazakhstan.

Structural and functional alterations within the Papez circuit in subacute stroke patients

Beyond causing local injury, stroke disrupts structural and functional organization of the brain networks, exposing patients to a high risk of cognitive impairment by affecting the neural network activity. However, the impact of these pathological changes on cognition-related neural circuits is not well understood. In this study, we mainly focused on structures and directed functional connectivity within the Papez circuit in subacute stroke patients. Forty-five stroke patients and thirty-four age-, sex-matched healthy controls were included in our study. The Papez circuit gray matter were measured to explore ischemia-induced structural alterations. And Granger causality analysis with the hippocampus as seed regions was performed to identify alterations of directional functional connectivity within the neural circuit. We also explored the associations between cerebral changes with cognitive status. Compared with healthy controls, stroke patients revealed marked atrophy in gray matter of the Papez circuit, including ipsilateral hippocampus, amygdala, thalamus, and caudal anterior cingulate gyrus. Additionally, there are alterations in the directed functional connections between the bilateral hippocampus and cingulate gyrus within the Papez circuit. These altered effective connectivities were correlated with cognitive function after cerebrovascular event. Taken together, in the early post-stroke period, disruptions of the Papez circuit in both architecture and directed functional connectivity have already occurred and might affect the cognitive function. These findings have prompted researchers to better understand the potential mechanisms underlying vascular cognitive impairment and to investigate new therapeutic targets that could reduce cognitive burden.

Long-Term Cognitive Decline After Stroke: An Individual Participant Data Meta-Analysis

BACKGROUND AND PURPOSE

Poststroke cognitive impairment is common, but the trajectory and magnitude of cognitive decline after stroke is unclear. We examined the course and determinants of cognitive change after stroke using individual participant data from the Stroke and Cognition Consortium.

METHODS

Nine longitudinal hospital-based cohorts from 7 countries were included. Neuropsychological test scores and normative data were used to calculate standardized scores for global cognition and 5 cognitive domains. One-step individual participant data meta-analysis was used to examine the rate of change in cognitive function and risk factors for cognitive decline after stroke. Stroke-free controls were included to examine rate differences. Based on the literature and our own data that showed short-term improvement in cognitive function after stroke, key analyses were restricted to the period beginning 1-year poststroke to focus on its long-term effects.

RESULTS

A total of 1488 patients (mean age, 66.3 years; SD, 11.1; 98% ischemic stroke) were followed for a median of 2.68 years (25th-75th percentile: 1.21-4.14 years). After an initial period of improvement through up to 1-year poststroke, decline was seen in global cognition and all domains except executive function after adjusting for age, sex, education, vascular risk factors, and stroke characteristics (-0.053 SD/year [95% CI, -0.073 to -0.033]; P<0.001 for global cognition). Recurrent stroke and older age were associated with faster decline. Decline was significantly faster in patients with stroke compared with controls (difference=-0.078 SD/year [95% CI, -0.11 to -0.045]; P<0.001 for global cognition in a subgroup analysis).

CONCLUSIONS

Patients with stroke experience cognitive decline that is faster than that of stroke-free controls from 1 to 3 years after onset. An increased rate of decline is associated with older age and recurrent stroke.

Predicting post-stroke cognitive impairment using acute CT neuroimaging: A systematic review and meta-analysis

Background

Identifying whether acute stroke patients are at risk of cognitive decline could improve prognostic discussions and management. Structural computed tomography neuroimaging is routine in acute stroke, and may identify those at risk of post-stroke dementia or post-stroke cognitive impairment (PSCI).

Aim

To systematically review the literature to identify which stroke or pre-stroke features on brain computed tomography scans, performed at the time of stroke, are associated with post-stroke dementia or PSCI.

Summary of review

We searched electronic databases to December 2020. We included studies reporting acute stroke brain computed tomography, and later diagnosis of a cognitive syndrome. We created summary estimates of size of unadjusted association between computed tomography features and cognition. Of 9536 citations, 28 studies (41 papers) were eligible (N = 7078, mean age 59.8–78.6 years). Cognitive outcomes were post-stroke dementia (10 studies), PSCI (17 studies), and one study analyzed both. Fifteen studies (N = 2952) reported data suitable for meta-analyses. White matter lesions (WML) (six studies, N = 1054, OR = 2.46, 95% CI = 1.25–4.84), cerebral atrophy (four studies, N = 558, OR = 2.80, 95% CI = 1.21–6.51), and pre-existing stroke lesions (three studies, N = 352, OR = 2.38, 95% CI = 1.06–5.32) were associated with post-stroke dementia. WML (four studies, N = 473, OR = 3.46, 95% CI = 2.17–5.52) were associated with PSCI. Other computed tomography features were either not associated with cognitive outcome, or there were insufficient data.

Conclusions

Cognitive impairment following stroke is of great concern to patients and carers. Features seen on visual assessment of acute stroke computed tomography brain scans are strongly associated with cognitive outcomes. Clinicians should consider when and how this information should be discussed with stroke survivors.

European Stroke Organisation and European Academy of Neurology joint guidelines on post-stroke cognitive impairment

The optimal management of post-stroke cognitive impairment remains controversial. These joint European Stroke Organisation (ESO) and European Academy of Neurology (EAN) guidelines provide evidence-based recommendations to assist clinicians in decision making around prevention, diagnosis, treatment and prognosis. These guidelines were developed according to ESO standard operating procedure and the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) methodology. The working group identified relevant clinical questions, performed systematic reviews and, where possible, meta-analyses of the literature, assessed the quality of the available evidence and made specific recommendations. Expert consensus statements were provided where insufficient evidence was available to provide recommendations based on the GRADE approach. There was limited randomised controlled trial evidence regarding single or multicomponent interventions to prevent post-stroke cognitive decline. Interventions to improve lifestyle and treat vascular risk factors may have many health benefits but a beneficial effect on cognition is not proven. We found no evidence around routine cognitive screening following stroke but recognise the importance of targeted cognitive assessment. We described the accuracy of various cognitive screening tests but found no clearly superior approach to testing. There was insufficient evidence to make a recommendation for use of cholinesterase inhibitors, memantine nootropics or cognitive rehabilitation. There was limited evidence on the use of prediction tools for post-stroke cognitive syndromes (cognitive impairment, dementia and delirium). The association between post-stroke cognitive impairment and most acute structural brain imaging features was unclear, although the presence of substantial white matter hyperintensities of presumed vascular origin on acute MRI brain may help predict cognitive outcomes. These guidelines have highlighted fundamental areas where robust evidence is lacking. Further, definitive randomised controlled trials are needed, and we suggest priority areas for future research.

Ongoing Secondary Degeneration of the Limbic System in Patients With Ischemic Stroke: A Longitudinal MRI Study

Purpose: Ongoing post-stroke structural degeneration and neuronal loss preceding neuropsychological symptoms such as cognitive decline and depression are poorly understood. Various substructures of the limbic system have been linked to cognitive impairment. In this longitudinal study, we investigated the post-stroke macro- and micro-structural integrity of the limbic system using structural and diffusion tensor magnetic resonance imaging.

Materials and Methods: Nineteen ischemic stroke patients (11 men, 8 women, average age 53.4 ± 12.3, range 18–75 years), with lesions remote from the limbic system, were serially imaged three times over 1 year. Structural and diffusion-tensor images (DTI) were obtained on a 3.0 T MRI system. The cortical thickness, subcortical volume, mean diffusivity (MD), and fractional anisotropy (FA) were measured in eight different regions of the limbic system. The National Institutes of Health Stroke Scale (NIHSS) was used for clinical assessment. A mixed model for multiple factors was used for statistical analysis, and p-values <0.05 was considered significant.

Results: All patients demonstrated improved NIHSS values over time. The ipsilesional subcortical volumes of the thalamus, hippocampus, and amygdala significantly decreased (p < 0.05) and MD significantly increased (p < 0.05). The ipsilesional cortical thickness of the entorhinal and perirhinal cortices was significantly smaller than the contralesional hemisphere at 12 months (p < 0.05). The cortical thickness of the cingulate gyrus at 12 months was significantly decreased at the caudal and isthmus regions as compared to the 1 month assessment (p < 0.05). The cingulum fibers had elevated MD at the ipsilesional caudal-anterior and posterior regions compared to the corresponding contralesional regions.

Conclusion: Despite the decreasing NIHSS scores, we found ongoing unilateral neuronal loss/secondary degeneration in the limbic system, irrespective of the lesion location. These results suggest a possible anatomical basis for post stroke psychiatric complications.

Systematic review and meta-analysis of the prevalence of cognitive impairment no dementia in the first year post-stroke

Introduction

Increasing attention is being paid to interventions for cognitive impairment (CI) post-stroke, including for CI that does not meet dementia criteria. The aim of this paper was to conduct a systematic review and meta-analysis of the prevalence of cognitive impairment no dementia (CIND) within one year post-stroke.

Patients and methods

Pubmed, EMBASE and PsychInfo were searched for papers published in English in 1995-2017. Included studies were population or hospital-based cohort studies for first-ever/recurrent stroke, assessing CIND using standardised criteria at 1-12 months post-stroke. Abstracts were screened, followed by full text review of potentially relevant articles. Data were extracted using a standard form, and study quality was appraised using the Crowe Critical Appraisal Tool. A pooled prevalence of CIND with 95% confidence intervals (CI) was estimated using random-effects meta-analysis. Heterogeneity was measured using the I² statistic.

Results

A total of 7000 abstracts were screened, followed by 1028 full text articles. Twenty-three articles were included in the systematic review, and 21 in the meta-analysis. The pooled CIND prevalence was 38% [95% CI = 32-43%] (I²=92.5%, p < 0.01). Study quality emerged as one source of heterogeneity. The five studies with the highest quality scores had no heterogeneity (I²=0%, p = 0.99), with a similar pooled prevalence (39%, 95%CI = 35-42%). Other sources of heterogeneity were stroke type, inclusion of pre-stroke CI, and age at assessment time.Discussion and conclusion: Meta-analysis of available studies indicates that in the first year post-stroke, 4 in 10 patients display a level of cognitive impairment that does not meet the criteria for dementia.

Compromised Motor Dexterity Confounds Processing Speed Task Outcomes in Stroke Patients

Most conventional measures of information processing speed require motor responses to facilitate performance. However, although not often addressed clinically, motor impairment, whether due to age or acquired brain injury, would be expected to confound the outcome measure of such tasks. The current study recruited 29 patients (20 stroke and 9 transient ischemic attack) with documented reduction in dexterity of the dominant hand, and 29 controls, to investigate the extent to which 3 commonly used processing speed measures with varying motor demands (a Visuo-Motor Reaction Time task, and the Wechsler Adult Intelligence Scale-IV Symbol Search and Coding subtests) may be measuring motor-related speed more so than cognitive speed. Analyses include correlations between indices of cognitive and motor speed obtained from two other tasks (Inspection Time and Pegboard task, respectively) with the three speed measures, followed by hierarchical regressions to determine the relative contribution of cognitive and motor speed indices toward task performance. Results revealed that speed outcomes on tasks with relatively high motor demands, such as Coding, were largely reflecting motor speed in individuals with reduced dominant hand dexterity. Thus, findings indicate the importance of employing measures with minimal motor requirements, especially when the assessment of speed is aimed at understanding cognitive rather than physical function.

Thalamic alterations remote to infarct appear as focal iron accumulation and impact clinical outcome

See Duering and Schmidt (doi:10.1093/awx135) for a scientific commentary on this article.Thalamic alterations have been observed in infarcts initially sparing the thalamus but interrupting thalamo-cortical or cortico-thalamic projections. We aimed at extending this knowledge by demonstrating with in vivo imaging sensitive to iron accumulation, one marker of neurodegeneration, that (i) secondary thalamic alterations are focally located in specific thalamic nuclei depending on the initial infarct location; and (ii) such secondary alterations can contribute independently to the long-term outcome. To tackle this issue, 172 patients with an infarct initially sparing the thalamus were prospectively evaluated clinically and with magnetic resonance imaging to quantify iron through R2* map at 24-72 h and at 1-year follow-up. An asymmetry index was used to compare R2* within the thalamus ipsilateral versus contralateral to infarct and we focused on the 95th percentile of R2* as a metric of high iron content. Spatial distribution within the thalamus was analysed on an average R2* map from the entire cohort. The asymmetry index of the 95th percentile within individual nuclei (medio-dorsal, pulvinar, lateral group) were compared according to the initial infarct location in simple and multiple regression analyses and using voxel-based lesion-symptom mapping. Associations between the asymmetry index of the 95th percentile and functional, cognitive and emotional outcome were calculated in multiple regression models. We showed that R2* was not modified at 24-72 h but showed heterogeneous increase at 1 year mainly within the medio-dorsal and pulvinar nuclei. The asymmetry index of the 95th percentile within the medio-dorsal nucleus was significantly associated with infarcts involving anterior areas (frontal P = 0.05, temporal P = 0.02, lenticular P = 0.01) while the asymmetry index of the 95th percentile within the pulvinar nucleus was significantly associated with infarcts involving posterior areas (parietal P = 0.046, temporal P < 0.001) independently of age, gender and infarct volume, which was confirmed by voxel-based lesion-symptom mapping. The asymmetry index of the 95th percentile within the entire thalamus at 1 year was independently associated with poor functional outcome (P = 0.04), poor cognitive outcome (P = 0.03), post-stroke anxiety (P = 0.04) and post-stroke depression (P = 0.02). We have therefore identified that iron accumulates within the thalamus ipsilateral to infarct after a delay with a focal distribution that is strongly linked to the initial infarct location (in relation with the pattern of connectivity between thalamic nuclei and cortical areas or deep nuclei), which independently contributes to functional, cognitive and emotional outcome.

Post-stroke dementia - a comprehensive review

Post-stroke dementia (PSD) or post-stroke cognitive impairment (PSCI) may affect up to one third of stroke survivors. Various definitions of PSCI and PSD have been described. We propose PSD as a label for any dementia following stroke in temporal relation. Various tools are available to screen and assess cognition, with few PSD-specific instruments. Choice will depend on purpose of assessment, with differing instruments needed for brief screening (e.g., Montreal Cognitive Assessment) or diagnostic formulation (e.g., NINDS VCI battery). A comprehensive evaluation should include assessment of pre-stroke cognition (e.g., using Informant Questionnaire for Cognitive Decline in the Elderly), mood (e.g., using Hospital Anxiety and Depression Scale), and functional consequences of cognitive impairments (e.g., using modified Rankin Scale). A large number of biomarkers for PSD, including indicators for genetic polymorphisms, biomarkers in the cerebrospinal fluid and in the serum, inflammatory mediators, and peripheral microRNA profiles have been proposed. Currently, no specific biomarkers have been proven to robustly discriminate vulnerable patients ('at risk brains') from those with better prognosis or to discriminate Alzheimer's disease dementia from PSD. Further, neuroimaging is an important diagnostic tool in PSD. The role of computerized tomography is limited to demonstrating type and location of the underlying primary lesion and indicating atrophy and severe white matter changes. Magnetic resonance imaging is the key neuroimaging modality and has high sensitivity and specificity for detecting pathological changes, including small vessel disease. Advanced multi-modal imaging includes diffusion tensor imaging for fiber tracking, by which changes in networks can be detected. Quantitative imaging of cerebral blood flow and metabolism by positron emission tomography can differentiate between vascular dementia and degenerative dementia and show the interaction between vascular and metabolic changes. Additionally, inflammatory changes after ischemia in the brain can be detected, which may play a role together with amyloid deposition in the development of PSD. Prevention of PSD can be achieved by prevention of stroke. As treatment strategies to inhibit the development and mitigate the course of PSD, lowering of blood pressure, statins, neuroprotective drugs, and anti-inflammatory agents have all been studied without convincing evidence of efficacy. Lifestyle interventions, physical activity, and cognitive training have been recently tested, but large controlled trials are still missing.