Longitudinal Brain Changes After Stroke and the Association With Cognitive Decline

Alterations of static and dynamic changes in intrinsic brain activity and its relation to behavioral outcomes in subcortical ischemic stroke after one-month intervention

Ischemic stroke is a prominent contributor to cognitive dysfunction and disability. Gaining a comprehensive understanding of the neuronal activity and longitudinal changes underlying stroke is crucial for designing effective rehabilitative strategies. However, the neural mechanisms responsible for the longitudinal reorganization of neuronal activity following stroke remain unclear. The objective of this study was to comprehensively investigate potential abnormalities in brain activity among stroke patients before and after one month of intervention (antiplatelet therapy, as well as intravenous citicoline). To achieve this goal, we combined static and dynamic functional imaging indicators for the comprehensive analysis. Twenty ischemic stroke patients at the subacute stage and seventeen age-matched healthy controls were included in the final analysis of this study from one center. Additionally, resting-state functional magnetic imaging scans were conducted on all patients twice with a one-month interval between scans. Four static intrinsic brain activity indicators (static amplitude of low-frequency fluctuation (sALFF), static fractional amplitude of low-frequency fluctuation (sfALFF), static regional homogeneity (sReHo), and static degree centrality (sDC)), along with their corresponding dynamic indicators, were calculated to detect longitudinal alterations in brain activity following stroke onset. Correlation analyses were also performed between these indicators within areas exhibiting group differences as well as clinical scale scores and disease duration. Significant variations in these static and dynamic image indicators were observed among patients with ischemic stroke. There was substantial overlap among the abnormal brain regions detected, primarily including decreased sALFF/sfALFF/dALFF in the bilateral central precuneus, increased sfALFF/sReHo/sDC/dReHo in the left superior precuneus, increased sALFF/sReHo/dfALFF in the left inferior temporal gyrus, decreased sReHo/sDC in the anterior cingulate cortex, increased sReHo/dfALFF in the right inferior parietal lobe, increased sfALFF/sDC in the right fusiform gyrus, as well as decreased sALFF/dALFF and increased sReHo/sDC in the right angular gyrus. Furthermore, these disrupted image indicators in some regions exhibited only partial recovery at the second time point. The percentage changes of these image indicators (sfALFF in the bilateral central precuneus, sDC in the left fusiform and dALFF in the right central precuneus) between the two time points were positively correlated with the percentage changes of clinical scores (FMA and MBI). In combination, this study demonstrates that a comprehensive understanding of abnormal activity and its longitudinal changes in ischemic stroke can be achieved by integrating static and dynamic imaging methods. Regions showing significant overlap among different brain activity indicators and exhibiting consistent image-behavior relationships may have some potential values for predicting clinical outcomes.

Differences in motor network reorganization between patients with good and poor upper extremity impairment outcomes after stroke

Changes in cortical excitability after stroke are closely associated with motor function recovery. This study aimed to clarify the motor network reorganization mechanisms corresponding to the different clinical outcomes of upper limb motor impairment in patients with subacute stroke. Motor function was assessed before rehabilitation (pre), after rehabilitation (post), and at the 1-year follow-up (follow-up) using the Fugl-Meyer assessment upper extremity scale. Further, resting-state functional magnetic resonance imaging (fMRI) data were collected in both pre- and post-conditions. Twenty patients with stroke were categorized into good and poor outcome groups based on motor impairments at the 1-year follow-up. Functional connections between motor-related regions of interest and the rest of the brain were subsequently calculated. Finally, the correlation between motor network reorganization and behavioral improvement at the 1-year follow-up was analyzed. The good outcome group exhibited a positive precondition motor function and continuous improvement, whereas the poor outcome group showed a weak precondition motor function and insignificant improvement. Contralesional hemisphere-related connections were found to be higher in the good outcome group pre-conditioning, with both groups showing minimal change post-conditioning, while no relationship with motor impairment was found. Long interhemispheric connections were decreased and increased in the good and poor outcome groups respectively, and were negatively correlated with motor impairment. Different motor network reorganizations during the subacute phase can influence the varying motor outcomes in the affected upper limb after stroke. These findings may serve as the theoretical basis for future neuromodulatory research.

Hippocampal atrophy and white matter lesions characteristics can predict evolution to dementia in patients with vascular mild cognitive impairment

BACKGROUND

Vascular mild cognitive impairment (VMCI) is a transitional condition that may evolve into Vascular Dementia(VaD). Hippocampal volume (HV) is suggested as an early marker for VaD, the role of white matter lesions (WMLs) in neurodegeneration remains debated.

OBJECTIVES

Evaluate HV and WMLs as predictive markers of VaD in VMCI patients by assessing: (i)baseline differences in HV and WMLs between converters to VaD and non-converters, (ii) predictive power of HV and WMLs for VaD, (iii) associations between HV, WMLs, and cognitive decline, (iv)the role of WMLs on HV.

METHODS

This longitudinal multicenter study included 110 VMCI subjects (mean age:74.33 ± 6.63 years, 60males/50females) from the VMCI-Tuscany Study database. Subjects underwent brain MRI and cognitive testing, with 2-year follow-up data on VaD progression. HV and WMLs were semi-automatically segmented and measured. ANCOVA assessed group differences, while linear and logistic regression models evaluated predictive power.

RESULTS

After 2 years, 32/110 VMCI patients progressed to VaD. Converting patients had lower HV(p = 0.015) and higher lesion volumes in the posterior thalamic radiation (p = 0.046), splenium of the corpus callosum (p = 0.016), cingulate gyrus (p = 0.041), and cingulum hippocampus(p = 0.038). HV alone did not fully explain progression (p = 0.059), but combined with WMLs volume, the model was significant (p = 0.035). The best prediction model (p = 0.001) included total HV (p = 0.004) and total WMLs volume of the posterior thalamic radiation (p = 0.005) and cingulate gyrus (p = 0.005), achieving 80% precision, 81% specificity, and 74% sensitivity. Lower HV were linked to poorer performance on the Rey Auditory-Verbal Learning Test delayed recall (RAVLT) and Mini Mental State Examination (MMSE).

CONCLUSIONS

HV and WMLs are significant predictors of progression from VMCI to VaD. Lower HV correlate with worse cognitive performance on RAVLT and MMSE tests.

Alterations of contralesional hippocampal subfield volumes and relations to cognitive functions in patients with unilateral stroke

BACKGROUND

The volumes of the hippocampal subfields are related to poststroke cognitive dysfunctions. However, it remains unclear whether contralesional hippocampal subfield volume contributes to cognitive impairment. This study aimed to investigate the volumetric differences in the contralesional hippocampal subfields between patients with left and right hemisphere strokes (LHS/RHS). Additionally, correlations between contralesional hippocampal subfield volumes and clinical outcomes were explored.

METHODS

Fourteen LHS (13 males, 52.57 ± 7.10 years), 13 RHS (11 males, 51.23 ± 15.23 years), and 18 healthy controls (11 males, 46.94 ± 12.74 years) were enrolled. Contralesional global and regional hippocampal volumes were obtained with T1-weighted images. Correlations between contralesional hippocampal subfield volumes and clinical outcomes, including the Montreal Cognitive Assessment (MoCA) and Mini-Mental State Examination (MMSE), were analyzed. Bonferroni correction was applied for multiple comparisons.

RESULTS

Significant reductions were found in contralesional hippocampal as a whole (adjusted p = .011) and its subfield volumes, including the hippocampal tail (adjusted p = .005), cornu ammonis 1 (CA1) (adjusted p = .002), molecular layer (ML) (adjusted p = .004), granule cell and ML of the dentate gyrus (GC-ML-DG) (adjusted p = .015), CA3 (adjusted p = .009), and CA4 (adjusted p = .014) in the RHS group compared to the LHS group. MoCA and MMSE had positive correlations with volumes of contralesional hippocampal tail (p = .015, r = .771; p = .017, r = .763) and fimbria (p = .020, r = .750; p = .019, r = .753) in the LHS group, and CA3 (p = .007, r = .857; p = .009, r = .838) in the RHS group, respectively.

CONCLUSION

Unilateral stroke caused volumetric differences in different hippocampal subfields contralesionally, which correlated to cognitive impairment. RHS leads to greater volumetric reduction in the whole contralesional hippocampus and specific subfields (hippocampal tail, CA1, ML, GC-ML-DG, CA3, and CA4) compared to LHS. These changes are correlated with cognitive impairments, potentially due to disrupted neural pathways and interhemispheric communication.

Dopaminergic mesolimbic structural reserve is positively linked to better outcome after severe stroke

The concept of brain reserve capacity has emerged in stroke recovery research in recent years. Imaging-based biomarkers of brain health have helped to better understand outcome variability in clinical cohorts. Still, outcome inferences are far from being satisfactory, particularly in patients with severe initial deficits. Neurorehabilitation after stroke is a complex process, comprising adaption and learning processes, which, on their part, are critically influenced by motivational and reward-related cognitive processes. Amongst others, dopaminergic neurotransmission is a key contributor to these mechanisms. The question arises, whether the amount of structural reserve capacity in the dopaminergic system might inform about outcome variability after severe stroke. For this purpose, this study analysed imaging and clinical data of 42 severely impaired acute stroke patients. Brain volumetry was performed within the first 2 weeks after the event using the Computational Anatomy Toolbox CAT12, grey matter volume estimates were collected for seven key areas of the human dopaminergic system along the mesocortical, mesolimbic and nigrostriatal pathways. Ordinal logistic regression models related regional volumes to the functional outcome, operationalized by the modified Rankin Scale, obtained 3-6 months after stroke. Models were adjusted for age, lesion volume and initial impairment. The main finding was that larger volumes of the amygdala and the nucleus accumbens at baseline were positively associated with a more favourable outcome. These data suggest a link between the structural state of mesolimbic key areas contributing to motor learning, motivational and reward-related brain networks and potentially the success of neurorehabilitation. They might also provide novel evidence to reconsider dopaminergic interventions particularly in severely impaired stroke patients to enhance recovery after stroke.

Predictors of Cognitive Functions After Stroke Assessed Using the Wechsler Adult Intelligence Scale: A Retrospective Study

Background

The mechanism(s) of cognitive impairment remains complex, making it difficult to confirm the factors influencing poststroke cognitive impairment (PSCI).

Objective

This study quantitatively investigated the degree of influence and interactions of clinical indicators of PSCI.

Methods

Information from 270 patients with PSCI and their Wechsler Adult Intelligence Scale (WAIS-RC) scores, totaling 18 indicators, were retrospectively collected. Correlations between the indicators and WAIS scores were calculated. Multiple linear regression model(MLR), genetic algorithm modified Back-Propagation neural network(GA-BP), logistic regression model (LR), XGBoost model (XGB), and structural equation model were used to analyze the degree of influence of factors on the WAIS and their mediating effects.

Results

Seven indicators were significantly correlated with the WAIS scores: education, lesion side, aphasia, frontal lobe, temporal lobe, diffuse lesions, and disease course. The MLR showed significant effect of education, lesion side, aphasia, diffuse lesions, and frontal lobe on the WAIS. The GA-BP included five factors: education, aphasia, frontal lobe, temporal lobe, and diffuse lesions. LR predicted that the lesion side contributed more to mild cognitive impairment, while education, lesion side, aphasia, and course of the disease contributed more to severe cognitive impairment. XGB showed that education, side of the lesion, aphasia, and diffuse lesions contributed the most to PSCI. Aphasia plays a significant mediating role in patients with severe PSCI.

Conclusions

Education, lesion side, aphasia, frontal lobe, and diffuse lesions significantly affected PSCI. Aphasia is a mediating variable between clinical information and the WAIS in patients with severe PSCI.

Neuroanatomical correlates of cognitive impairment following basal ganglia-thalamic post-hemorrhagic stroke: Uncovering network-wide alterations in hemispheric gray matter asymmetry

Cognitive impairment and recovery are central issues in hemorrhagic stroke. This study aimed to investigate whether post-hemorrhagic stroke cognitive impairment (PhSCI) is associated with cortical gray matter (GM) loss and hemispheric asymmetry changes and whether these changes could predict improvements in cognitive function during the recovery. Nineteen patients with PhSCI, comprising 10 with basal ganglia hemorrhage and 9 with thalamic hemorrhage, were recruited. Among them, 9 completed a course of repetitive transcranial magnetic stimulation (rTMS). Additionally, 19 demographically and comorbidity-matched healthy controls were also included. Structural brain MRI and cognitive assessments were performed. Voxel-wise GM volume and hemispheric asymmetry were analyzed. The PhSCI patients exhibited bilateral, yet asymmetric, GM losses in the hippocampus, fusiform, lateral temporal, prefrontal, somatomotor, and inferior parietal regions. The analysis of GM asymmetry revealed that patients showed rightward GM in the lateral temporal, somatomotor, and inferior parietal regions. Among the 9 PhSCI patients who completed rTMS, there was a marginal trend of regional GM increase and leftward GM, and these changes were in parallel with the improvements in cognitive tests. Further lesion connectivity and metanalytic mapping identified two interconnected systems linked to the lesions, which were anchored in the default mode, somatomotor, and salience/cognitive control networks and in the cognitive domains of memory, language, decision-making, and executive function. In conclusion, PhSCI patients exhibited network-wide cortical GM losses, distal to subcortical hemorrhagic lesions, and hemisphere asymmetry changes. These changes appear to predict rTMS-related cognitive improvements, suggesting that even subcortical focal lesions can lead to alterations in distal cortical neuroanatomical architecture. Our preliminary findings provide new insights into the neuroanatomical basis of PhSCI.

Secondary neurodegeneration following Stroke: what can blood biomarkers tell us?

Stroke is one of the leading causes of death and the primary source of disability in adults, resulting in neuronal necrosis of ischemic areas, and in possible secondary degeneration of regions surrounding or distant to the initial damaged area. Secondary neurodegeneration (SNDG) following stroke has been shown to have different pathogenetic origins including inflammation, neurovascular response and cytotoxicity, but can be associated also to regenerative processes. Aside from focal neuronal loss, ipsilateral and contralateral effects distal to the lesion site, disruptions of global functional connectivity and a transcallosal diaschisis have been reported in the chronic stages after stroke. Furthermore, SNDG can be observed in different areas not directly connected to the primary lesion, such as thalamus, hippocampus, amygdala, substantia nigra, corpus callosum, bilateral inferior fronto-occipital fasciculus and superior longitudinal fasciculus, which can be highlighted by neuroimaging techniques. Although the clinical relevance of SNDG following stroke has not been well understood, the identification of specific biomarkers that reflect the brain response to the damage, is of paramount importance to investigate in vivo the different phases of stroke. Actually, brain-derived markers, particularly neurofilament light chain, tau protein, S100b, in post-stroke patients have yielded promising results. This review focuses on cerebral morphological modifications occurring after a stroke, on associated cellular and molecular changes and on state-of-the-art of biomarkers in acute and chronic phase. Finally, we discuss new perspectives regarding the implementation of blood-based biomarkers in clinical practice to improve the rehabilitation approaches and post stroke recovery.

Morphological alterations of contralesional hemisphere relate to functional outcomes after stroke

The present study aimed to investigate poststroke morphological alterations contralesionally and correlations with functional outcomes. Structural magnetic resonance images were obtained from 27 poststroke patients (24 males, 50.21 ± 10.97 years) and 20 healthy controls (13 males, 46.63 ± 12.18 years). Voxel-based and surface-based morphometry analysis were conducted to detect alterations of contralesional grey matter volume (GMV), cortical thickness (CT), gyrification index (GI), sulcus depth (SD), and fractal dimension (FD) in poststroke patients. Partial correlation analysis was used to explore the relationship between regions with significant structural differences and scores of clinical assessments, including Modified Barthel Index (MBI), Berg Balance Scale (BBS), Fugl-Meyer Assessment of Upper Extremity (FMA-UE), Mini-Mental State Examination (MMSE), and Montreal Cognitive Assessment (MoCA). Correction for multiplicity was conducted within each parameter and for all tests. GMV significantly decreased in the contralesional motor-related, occipital and temporal cortex, limbic system, and cerebellum lobe (P < 0.01, family-wise error [FWE] correction). Lower CT was found in the contralesional precentral and lingual gyrus (P < 0.01, FWE correction), while lower GI found in the contralesional superior temporal gyrus and insula (P < 0.01, FWE correction). There were significant correlations between GMV of contralesional lingual gyrus and MBI (P = 0.031, r = 0.441), and BBS (P = 0.047, r = 0.409) scores, and GMV of contralesional hippocampus and FMA-UE scores (P = 0.048, r = 0.408). In conclusion, stroke patients exhibited wide grey matter loss and cortical morphological changes in the contralesional hemisphere, which correlated with sensorimotor functions and the ability of daily living.

Multimodal individualised intervention to prevent functional decline after stroke: protocol of a randomised controlled trial on long-term follow-up after stroke (LAST-long)

INTRODUCTION

Multimodal interventions have emerged as new approaches to provide more targeted intervention to reduce functional decline after stroke. Still, the evidence is contradictory. The main objective of the Life After Stroke (LAST)-long trial is to investigate if monthly meetings with a stroke coordinator who offers a multimodal approach to long-term follow-up can prevent functional decline after stroke.

METHODS AND ANALYSIS

LAST-long is a pragmatic single-blinded, parallel-group randomised controlled trial recruiting participants living in six different municipalities, admitted to four hospitals in Norway. The patients are screened for inclusion and recruited into the trial 3 months after stroke. A total of 300 patients fulfilling the inclusion criteria will be randomised to an intervention group receiving monthly follow-up by a community-based stroke coordinator who identifies the participants' individual risk profile and sets up an action plan based on individual goals, or to a control group receiving standard care. All participants undergo blinded assessments at 6-month, 12-month and 18-month follow-up. Modified Rankin Scale at 18 months is primary outcome. Secondary outcomes are results of blood tests, blood pressure, adherence to secondary prophylaxis, measures of activities of daily living, cognitive function, physical function, physical activity, patient reported outcome measures, caregiver's burden, the use and costs of health services, safety measures and measures of adherence to the intervention. Mixed models will be used to evaluate differences between the intervention and control group for all endpoints across the four time points, with treatment group, time as categorical covariates and their interaction as fixed effects, and patient as random effect.

ETHICS AND DISSEMINATION

This trial was approved by the Regional Committee of Medical and Health Research Ethics, REC no. 2018/1809. The main results will be published in international peer-reviewed open access scientific journals and to policy-makers and end users in relevant channels.

TRIAL REGISTRATION NUMBER

ClincalTrials.gov Identifier: NCT03859063, registered on 1 March 2019.

The relationship between the prefrontal cortex and limb motor function in stroke: A study based on resting-state functional near-infrared spectroscopy

BACKGROUND

With the ageing of the world population, the incidence of stroke has been increasing annually, becoming a public health problem affecting adult health. Limb motor dysfunction is one of the common complications of stroke and an important factor in disability. Therefore, restoring limb function is an important task in current rehabilitation. Accurate assessment of motor function in stroke patients is the basis for formulating effective rehabilitation strategies. With the development of neuroimaging technology, scholars have begun to study objective evaluation methods for limb motor dysfunction in stroke to determine reliable neural biomarkers to accurately identify brain functional activity and its relationship with limb motor function. The prefrontal cortex (PFC) plays an important role in motor control and in response to motor state changes. Our previous study found that the PFC network characteristics of stroke patients are related to their motor function status and the topological properties of the PFC network under resting state can predict the motor function of stroke patients to some extent. Therefore, this study used functional near-infrared spectroscopy (fNIRS) to evaluate prefrontal neuroplasticity markers and the relationships between such neural markers and limb motor function in stroke patients with limb motor dysfunction, which could be helpful to further clarify the relationship between brain neuroplasticity and cerebral haemodynamics. At the same time, through accurate and objective means of evaluation, it could be helpful for clinicians to formulate and optimize individualized rehabilitation treatment plans and accurately determine the rehabilitation efficacy and prognosis.

METHODS

This study recruited 17 S patients with limb motor dysfunction and 9 healthy subjects. fNIRS was used to collect 22 channels of cerebral blood oxygen signals in the PFC in the resting state. The differences in prefrontal oxygenated haemoglobin (HbO) and deoxygenated haemoglobin (HbR) concentrations were analysed between stroke patients and healthy subjects, and the lateralization index (LI) of HbO in stroke patients was also calculated. Pearson's correlation analysis was performed between the LI and the scores of the Fugl-Meyer Assessment Scale (FMA) of motor function in stroke patients.

RESULTS

The results found that the prefrontal HbO concentration was significantly decreased in stroke patients with limb motor dysfunction compared with healthy subjects, and there was a significant, positive correlation between the LI of the PFC and FMA scores in stroke patients.

CONCLUSION

These study results showed that stroke can cause cerebral haemodynamic changes in the PFC, and the functional imbalance of the left and right PFC in the resting state is correlated with the severity of limb motor dysfunction. Furthermore, we emphasize that the cerebral haemodynamic activity reflected by fNIRS could be used as a reliable neural biomarker for assessing limb motor dysfunction in stroke.

Beyond the Primary Infarction: Focus on Mechanisms Related to Secondary Neurodegeneration after Stroke

Recently, a growing body of evidence has indicated that secondary neurodegeneration after stroke occurs at remote regions of the brain that are connected to the primary infarction site [...].