Withdrawn: The altered dynamic community structure for adaptive adjustment in stroke patients with multidomain cognitive impairments: A multilayer network analysis.

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Cortical structure reorganization and correlation with attention deficit in subcortical stroke: An underlying pattern analysis.

BACKGROUND: Subcortical stroke may significantly alter the cerebral cortical structure and affect attention function, but the details of this process remain unclear. The study aimed to investigate the neural substrates underlying attention impairment in patients with subcortical stroke. MATERIALS AND METHODS: In this prospective observational study, two distinct datasets were acquired to identify imaging biomarkers underlying attention deficit. The first dataset consisted of 86 patients with subcortical stroke, providing a cross-sectional perspective, whereas the second comprised 108 patients with stroke, offering longitudinal insights. All statistical analyses were subjected to false discovery rate correction upon P < 0.05. RESULTS: In the chronic-stage data, the stroke group exhibited significantly poorer attention function compared with that of the control group. The cortical structure analysis showed that patients with stroke exhibited decreased cortical thickness of the precentral gyrus and surface area of the cuneus, along with an increase in various frontal, occipital, and parietal cortices regions. The declined attention function positively correlated with the superior frontal gyrus cortical thickness and supramarginal gyrus surface area. In the longitudinal dataset, patients with stroke showed gradually increasing cortical thickness and surface area within regions of obvious structural reorganization. Furthermore, deficient attention positively correlated with supramarginal gyrus surface area both at the subacute and chronic stages post-stroke. CONCLUSIONS: Subcortical stroke can elicit dynamic reorganization of cortical areas associated with attention impairment. Moreover, the altered surface area of the supramarginal gyrus is a potential neuroimaging biomarker for attention deficits.

Altered static and dynamic cerebellar-cerebral functional connectivity in acute pontine infarction.

This study investigates abnormalities in cerebellar-cerebral static and dynamic functional connectivity among patients with acute pontine infarction, examining the relationship between these connectivity changes and behavioral dysfunction. Resting-state functional magnetic resonance imaging was utilized to collect data from 45 patients within seven days post-pontine infarction and 34 normal controls. Seed-based static and dynamic functional connectivity analyses identified divergences in cerebellar-cerebral connectivity features between pontine infarction patients and normal controls. Correlations between abnormal functional connectivity features and behavioral scores were explored. Compared to normal controls, left pontine infarction patients exhibited significantly increased static functional connectivity within the executive, affective-limbic, and motor networks. Conversely, right pontine infarction patients demonstrated decreased static functional connectivity in the executive, affective-limbic, and default mode networks, alongside an increase in the executive and motor networks. Decreased temporal variability of dynamic functional connectivity was observed in the executive and default mode networks among left pontine infarction patients. Furthermore, abnormalities in static and dynamic functional connectivity within the executive network correlated with motor and working memory performance in patients. These findings suggest that alterations in cerebellar-cerebral static and dynamic functional connectivity could underpin the behavioral dysfunctions observed in acute pontine infarction patients.

Dynamic brain activity states of memory impairment in stroke patients with varying motor outcomes.

Introduction: The objective of this study was to characterize the alteration patterns of dynamic spatiotemporal activity in chronic subcortical stroke patients with varying motor outcomes, while investigating the imaging indicators relevant to the assessment of potential cognitive deficits in these patients. Methods: A total of 136 patients and 88 normal controls were included in the analysis of static and dynamic intrinsic brain activity, determined by amplitude of low-frequency fluctuations. Results: The findings unveiled that subcortical stroke patients exhibited significantly aberrant temporal dynamics of intrinsic brain activity, involving regions within multiple brain networks. These spatiotemporal patterns were found to be contingent upon the side of the lesion. In addition, these aberrant metrics demonstrated potential in discerning cognitive deficits in stroke patients with memory impairment, with the dynamic indices exerting more influence than the static ones. The observe findings may indicate that subcortical stroke can trigger imbalances in the segregation and integration of spatiotemporal patterns across the entire brain with multi-domain networks, especially in patients with poor motor outcomes. Conclusion: It suggests that the temporal dynamics indices of intrinsic brain activity could serve as potential imaging indicators for assessing cognitive impairment in patients with chronic subcortical stroke, which may be associated with the motor outcomes.

Reduced GABA concentration in patients with white matter hyperintensities.

To investigate potential alterations of white matter hyperintensities (WMHs) on J-edited MR spectroscopy (MRS) measures of the primary inhibitory neurotransmitter γ-aminobutyric acid (GABA). Twenty-four WMHs patients and 20 healthy controls (HCs) were recruited to undergo magnetic resonance spectroscopy (MRS) scan at 3T from voxels in left centrum semiovale white matter, using the MEGA point resolved spectroscopy (MEGA-PRESS) technique with the MATLAB-based Gannet tool to estimate GABA+ co-edited macromolecule (GABA+) levels and using Tarquin software to estimate levels of glutamate + glutamine (Glx), total N-acetylaspartate (tNAA), total choline (tCho), and total creatine (tCr). Independent t-tests or Mann-Whitney U-tests were used to test group differences between WMHs and HCs. Additionally, WMHs patients were divided into mild and moderate-severe WMHs subgroup according to the Fazekas scale. Analysis of variance (ANOVA) and post-hoc tests were used among WMHs subgroups and HCs. We found there was a significant reduction in GABA+ levels (p = 0.018) in WMHs patients compared with healthy controls. In subgroup analyses, there was also a significant reduction of GABA+ levels in moderate-severe WMHs subgroup (p = 0.037) and mild WMHs subgroup (p = 0.047) when compared to HCs. Besides, the moderate-severe WMHs subgroup had significantly higher levels of tCho compared with healthy controls (p = 0.019). In conclusion, reduced GABA+ levels in WMHs patients and elevated tCho levels in moderate-severe WMHs were observed when compared with HCs. These results demonstrate that abnormalities of the GABAergic system and choline metabolism may contribute to the pathogenesis of WMHs.

Altered resting-state neurovascular coupling in patients with pontine infarction.

The risk for motor and cognitive impairment is increased in patients with chronic pontine infarction (PI). In this study, we attempted to explore the alterations of neurovascular coupling (NVC) in order to understand the neural basis of behavioral impairment after PI. Three-dimensional pseudo-continuous arterial spin labeling (3D-pcASL) and resting-state functional magnetic resonance imaging (rs-fMRI) were applied in 49 patients with unilateral PI (left-sided, n = 26; right-sided, n = 23) and 30 matched normal subjects to assess whole-brain cerebral blood flow (CBF) and functional connectivity strength (FCS). We evaluated NVC in each subject by calculating the correlation coefficient between the whole-brain CBF and FCS (CBF-FCS coupling) and the ratio between voxel-wise CBF and FCS (CBF/FCS ratio). The FCS maps were then divided into long-range and short-range FCS to identify the influence of connection distance. The results indicated that the CBF-FCS coupling in the whole-brain level was significantly interrupted in PI patients, and the CBF/FCS ratio in cognition-related brain regions was abnormal. Distance-dependent results demonstrated that PI had a more serious effect on long-range neurovascular coupling. Correlation analysis revealed that the changes in neurovascular coupling were correlated with working memory scores. These findings imply that disruption of neurovascular coupling in the remote-infarction brain regions may underlie the impaired cognitive functions in chronic PI.

Altered static and dynamic spontaneous neural activity in patients with ischemic pontine stroke.

Objective: The purpose of the study was to investigate the abnormality both of static spontaneous brain activity and dynamic temporal variances following a pontine infarction. Methods: Forty-six patients with chronic left pontine infarction (LPI), thirty-two patients with chronic right pontine infarction (RPI), and fifty healthy controls (HCs) were recruited for the study. The static amplitude of low-frequency fluctuations (sALFF), static regional homogeneity (sReHo), dynamic ALFF (dALFF), and dynamic ReHo (dReHo) were employed to detect the alterations in brain activity induced by an infarction. The Rey Auditory Verbal Learning Test and Flanker task were used to evaluate the verbal memory and visual attention function, respectively. Receiver operating characteristic curve analysis was used to reveal the potential capacity of these metrics to distinguish the patients from HCs. Results: There were significant variations of these static and dynamic metrics in patients with chronic pontine infarction. The altered regions involved the supratentorial regions, including cortex and subcortical. Moreover, the altered metrics were significantly correlated with verbal memory and visual attention. In addition, these static and dynamic metrics also showed potential in distinguishing stroke patients with behavior deficits from HCs. Conclusion: The pontine infarction-induced cerebral activation changes are observed in both motor and cognitive systems, indicating the functional damage and reorganization across the global cerebral level in these patients with subtentorial infarction, and there is a reciprocal effect between motor and cognitive impairment and repair.

Abnormal functional connectivities patterns of multidomain cognitive impairments in pontine stroke patients.

Cognitive dysfunction in patients with infratentorial stroke has been paid little attention. Brainstem stroke may disrupt network connectivity across the whole brain and affect multidomain cognition, but the details of this process remain unclear. The study aimed to investigate the effects of stroke-induced pontine injury on whole-brain network connectivity and cognitive function. We included 47 patients with pontine stroke and 56 healthy comparisons (HC), who underwent cognitive tests and functional magnetic resonance imaging (fMRI). Seven meaningful brain networks were identified using independent component analysis (ICA). Patients with pontine stroke had decreased intra-network functional connectivities (FCs) in the primary perceptual and higher cognitive control networks, including sensorimotor network (SMN), visual network (VIS), default mode network (DMN), and salience network (SAN), as well as decreased inter-network FCs in the primary perceptual (VIS-SMN) and higher cognitive control networks (bilateral frontoparietal networks, rFPN-lFPN). While the FCs between the primary perceptual and higher cognitive control networks (VIS-DMN, VIS-rFPN, VIS-lFPN) were increased. Furthermore, the alterations in these FCs correlated with patients' cognitive measurements. These findings suggested that the infratentorial stroke can induce dysfunctional connectivity in both primary perceptual and higher cognitive control networks at the whole-brain level, which may be attributable to the neural substrates of multidomain cognitive deficits in these patients.

Dynamic Relationship Between Interhemispheric Functional Connectivity and Corticospinal Tract Changing Pattern After Subcortical Stroke.

Background and Purpose: Increased interhemispheric resting-state functional connectivity (rsFC) between the bilateral primary motor cortex (M1) compensates for corticospinal tract (CST) impairment, which facilitates motor recovery in chronic subcortical stroke. However, there is a lack of data on the evolution patterns and correlations between M1-M1 rsFC and diffusion indices of CSTs with different origins after subcortical stroke and their relations with long-term motor outcomes. Methods: A total of 44 patients with subcortical stroke underwent longitudinal structural and functional magnetic resonance imaging (MRI) examinations and clinical assessments at four time points. Diffusion tensor imaging was used to extract fractional anisotropy (FA) values of the affected CSTs with different origins. Resting-state functional MRI was used to calculate the M1-M1 rsFC. Longitudinal patterns of functional and anatomic changes in connections were explored using a linear mixed-effects model. Dynamic relationships between M1-M1 rsFC and FA values of the affected specific CSTs and the impact of these variations on the long-term motor outcomes were analyzed in patients with subcortical stroke. Results: Stroke patients showed a significantly decreased FA in the affected specific CSTs and a gradually increasing M1-M1 rsFC from the acute to the chronic stage. The FA of the affected M1 fiber was negatively correlated with the M1-M1 rsFC from the subacute to the chronic stage, FA of the affected supplementary motor area fiber was negatively correlated with the M1-M1 rsFC in the subacute stage, and FA of the affected M1 fiber in the acute stage was correlated with the long-term motor recovery after subcortical stroke. Conclusion: Our findings show that the FA of the affected M1 fiber in the acute stage had the most significant correlation with long-term motor recovery and may be used as an imaging biomarker for predicting motor outcomes after stroke. The compensatory role of the M1-M1 rsFC enhancement may start from the subacute stage in stroke patients with CST impairment.

Longitudinal gray matter atrophy and accompanied functional connectivity alterations in patients with pontine infarction.

OBJECTIVES: To investigate the longitudinal changes in gray matter volume (GMV) and functional connectivity (FC) in patients with pontine infarction (PI) during a 6-month follow-up period. METHODS: Twenty-two patients underwent MRI scans and behavioral assessments at 1 week, 1 month, 3 months, and 6 months after PI. Twenty-two normal controls (NC) were administered once with a similar examination. Voxel-wise GMV analysis was used to investigate the difference between the 1 week of PI and NC groups. Longitudinal changes in GMV were assessed and then used as seed regions to explore the accompanying FC changes during the 6-month follow-up. Correlations of the behavioral scores with the imaging indices of clusters with altered GMV and FC were also investigated. RESULTS: The LPI group exhibited GMV atrophy in the left cerebellar Crus II, right cerebellar lobule VI, right Vermis VI, while the RPI group showed GMV atrophy in the left cerebellar Crus II. The significant decrease of GMV firstly appeared at 1 month and gradually decreased over time. When using brain regions with GMV atrophy as seeds, longitudinal analysis of FC showed a significant decrease between the left cerebellar Crus II and left middle frontal gyrus at 6 months in the LPI group. Furthermore, the longitudinally altered FC values were negatively correlated with motor scores over time. CONCLUSION: These findings provide evidence for progressive GMV atrophy in the cerebellum and impaired relative FC in patients with PI, which could provide vital information for investigating neural bases of behavioral recovery in PI.

Validation of cerebral blood flow connectivity as imaging prognostic biomarker on subcortical stroke.

Stroke is a major cause of vascular cognitive dysfunction, such as memory impairment. We aimed to explore the neural substrates underlying verbal memory impairment in subcortical stroke patients by the methods of voxel-wise cerebral blood flow (CBF) and the functional covariance network (FCN). Sixty patients with chronic subcortical stroke and 60 normal controls (NCs) were recruited into this study. We used a three-dimensional pseudo-continuous arterial spin-labeling imaging to measure alterations in CBF and FCNs. We mapped the overall CBF alterations in a voxel-wise manner and compared CBF measurements using a two-sample t test. Correlations between CBF and verbal memory were also investigated. Subsequently, we constructed FCNs by calculating the correlation between specific regions and all other voxels of a whole brain, separately within the two groups. Thereafter, by comparing differences of the FCN patterns between the patient and NC groups, we investigated the connection alterations within the FCN maps. The stroke patients showed verbal short-term memory (VSTM) deficits compared to NCs. The patients exhibited decreased CBF in the ipsilesional insula and ventral sensorimotor network, and increased CBF in contralesional frontal cortical and subcortical regions (putamen and thalamus). Meanwhile, the CBF in the ipsilesional insula was positively correlated, and the contralesional frontal cortical was negativity correlated, with VSTM scores. Moreover we found that stroke patients exhibited disordered connection within FCNs compared to NCs. The study suggests that the underlying imaging biomarker of VSTM impairment in patients with subcortical stroke was associated with disconnection of the frontal lobe network.

Voxel-Mirrored Homotopic Connectivity Associated With Change of Cognitive Function in Chronic Pontine Stroke.

Recent neuroimaging studies have shown the possibility of cognitive impairment after pontine stroke. In this study, we aimed to use voxel-mirrored homotopic connectivity (VMHC) to investigate changes in the cognitive function in chronic pontine stroke. Functional MRI (fMRI) and behavioral assessments of cognitive function were obtained from 56 patients with chronic pontine ischemic stroke [28 patients with left-sided pontine stroke (LP) and 28 patients with right-sided pontine stroke (RP)] and 35 matched healthy controls (HC). The one-way ANOVA test was performed for the three groups after the VMHC analysis. Results showed that there were significant decreases in the bilateral lingual gyrus (Lingual_L and Lingual_R) and the left precuneus (Precuneus_L) in patients with chronic pontine ischemic stroke compared to HCs. However, in a post-hoc multiple comparison test, this difference remained only between the HC and RP groups. Moreover, we explored the relationship between the decreased z-values in VMHC and the behavior-task scores using a Pearson's correlation test and found that both scores of short-term memory and long-term memory in the Rey Auditory Verbal Learning Test were positively correlated with z-values of the left lingual gyrus (Lingual_L), the right lingual gyrus (Lingual_R), and the left precuneus (Precuneus_L) in VMHC. Besides that, the z-values of Precuneus_L in VMHC were also negatively correlated with the reaction time for correct responses in the Flanker task and the spatial memory task. In conclusion, first, the lingual gyrus played an important role in verbal memory. Second, the precuneus influenced the working memory, both auditory-verbal memory and visual memory. Third, the right-sided stroke played a greater role in the results of this study. This study provides a basis for further elucidation of the characteristics and mechanisms of cognitive impairment after pontine stroke.

Widespread White Matter Microstructure Alterations Based on Diffusion Tensor Imaging and Diffusion Kurtosis Imaging in Patients With Pontine Infarction.

Neurological deficits after stroke are closely related to white matter microstructure damage. However, secondary changes in white matter microstructure after pontine infarction (PI) in the whole brain remain unclear. This study aimed to investigate the correlation of diffusion kurtosis imaging (DKI)-derived diffusion and kurtosis parameters of abnormal white matter tracts with behavioral function in patients with chronic PI. Overall, 60 patients with unilateral chronic PI (33 patients with left PI and 27 patients with right PI) and 30 normal subjects were recruited and underwent DKI scans. Diffusion parameters derived from diffusion tensor imaging (DTI) and DKI and kurtosis parameters derived from DKI were obtained. Between-group differences in multiple parameters were analyzed to assess the changes in abnormal white matter microstructure. Moreover, we also calculated the sensitivities of different diffusion and kurtosis parameters of DTI and DKI for identifying abnormal white matter tracts. Correlations between the DKI-derived parameters in secondary microstructure changes and behavioral scores in the PI were analyzed. Compared with the NC group, both left PI and right PI groups showed more extensive perilesional and remote white matter microstructure changes. The DKI-derived diffusion parameters showed higher sensitivities than did the DTI-derived parameters. Further, DKI-derived diffusion and kurtosis parameters in abnormal white matter regions were correlated with impaired motor and cognitive function in patients with PI. In conclusion, PI could lead to extensive white matter tracts impairment in perilesional and remote regions. Further, the diffusion and kurtosis parameters could be complementary for identifying comprehensive tissue microstructural damage after PI.

Disrupted Regional Cerebral Blood Flow and Functional Connectivity in Pontine Infarction: A Longitudinal MRI Study.

Abnormal cerebral blood flow (CBF) and resting-state functional connectivity (rs-FC) are sensitive biomarkers of disease progression and prognosis. This study investigated neural underpinnings of motor and cognitive recovery by longitudinally studying the changes of CBF and FC in pontine infarction (PI). Twenty patients underwent three-dimensional pseudo-continuous arterial spin labeling (3D-pcASL), resting-state functional magnetic resonance imaging (rs-fMRI) scans, and behavioral assessments at 1 week, 1, 3, and 6 months after stroke. Twenty normal control (NC) subjects underwent the same examination once. First, we investigated CBF changes in the acute stage, and longitudinal changes from 1 week to 6 months after PI. Brain regions with longitudinal CBF changes were then used as seeds to investigate longitudinal FC alterations during the follow-up period. Compared with NC, patients in the left PI (LPI) and right PI (RPI) groups showed significant CBF alterations in the bilateral cerebellum and some supratentorial brain regions at the baseline stage. Longitudinal analysis revealed that altered CBF values in the right supramarginal (SMG_R) for the LPI group, while the RPI group showed significantly dynamic changes of CBF in the left calcarine sulcus (CAL_L), middle occipital gyrus (MOG_L), and right supplementary motor area (SMA_R). Using the SMG_R as the seed in the LPI group, FC changes were found in the MOG_L, middle temporal gyrus (MTG_L), and prefrontal lobe (IFG_L). Correlation analysis showed that longitudinal CBF changes in the SMG_R and FC values between the SMG_R and MOG_L were associated with motor and memory scores in the LPI group, and longitudinal CBF changes in the CAL_L and SMA_R were related to memory and motor recovery in the RPI group. These longitudinal CBF and accompany FC alterations may provide insights into the neural mechanism underlying functional recovery after PI, including that of motor and cognitive functions.

Progressive Gray Matter Atrophy and Abnormal Structural Covariance Network in Ischemic Pontine Stroke.

Our aim was to identify the longitudinal changes in gray matter volume (GMV) and secondary alterations of structural covariance after pontine stroke (PS). Structural MRI and behavioral scores were obtained at 1 week, 1 month, 3 months, 6 months in 11 patients with PS. Twenty healthy subjects underwent the same examination only once. We used voxel-based morphometry and seed-based structural covariance to investigate the altered GMV and structural covariance patterns. Furthermore, the associations between the GMV changes and behavioral scores were assessed. With the progression of the disease, GMV decreased significantly in the bilateral cerebellar posterior lobe (ipsilateral Crus II (CBE Crus II_IL) and contralateral Crus I (CBE Crus I_CL)), which were initially detected at the first month and then continued to decrease during the following 6 months. Based on the CBE Crus II_IL and CBE Crus I_CL as seed regions, structural covariance analysis revealed that there were more positively and negatively correlated brain regions in PS group, mainly distributed in the bilateral prefrontal lobe, parietal lobe, temporal lobe, paralimbic system and cerebellum. In addition, PS group showed more additional correlations between these covariant brain regions, and the changes of GMV in these regions were correlated with behavioral scores related to motor and cognitive functions. These findings indicate that PS could lead to significant GMV atrophy in the bilateral cerebellar posterior lobe at the early stage, accompanied by anomalous structural covariance patterns with more covariant brain regions and additional structural connectivity, which may provide useful information for understanding the neurobiological mechanisms of behavioral recovery after PS.

An imbalance between functional segregation and integration in patients with pontine stroke: A dynamic functional network connectivity study.

BACKGROUND: Previous studies on brain functional connectivity have revealed the neural physiopathology in patients with pontine stroke (PS). However, those studies focused only on the static features of intrinsic fluctuations, rather than on the time-varying effects throughout the entire scan. In the present study, we sought to explore the underlying mechanism of PS using the dynamic functional network connectivity (dFNC) method. METHODS: Resting-state functional magnetic resonance imaging (fMRI) data were collected from 58 patients with PS and 52 healthy controls (HC). Independent component analysis (ICA), the sliding window method, and k-means clustering analysis were performed to extract different functional networks, to calculate dFNC matrices, and to estimate distinct dynamic connectivity states. Additionally, temporal features were compared between the two groups in each state to explore the brain's preference for different dynamic connectivity states in PS, and global and local efficiency were compared among states to explore the differences of topologic organization across different dFNC states. The correlations between clinical scales and the temporal features that differed between the two groups also were calculated. RESULTS: The dFNC analyses suggested four recurring states; in two of these states, the PS group showed a different duration from that of the HC group. Patients with PS spent significantly more time in a sparsely connected state (State 1), which was characterized by relatively low levels of connectivity within and between all brain networks. In contrast, patients with PS spent significantly less time in a highly segregated state (State 2), which was characterized by high levels of positive connectivities within primary perceptional domains and within higher cognitive control domains, and by high levels of negative inter-functional connectivities (inter-FCs) among primary perceptional and higher cognitive control domains. Additionally, the dwell time in State 2 was positively correlated with HC group's long-term memory scores in the Rey Auditory Verbal Learning Test (RAVLT-L), whereas there was no correlation between the State-2 dwell time and RAVLT-L scores in the PS group. Furthermore, the sparsely connected state and the highly segregated state mentioned above had the highest global efficiency and the highest local efficiency among the four states, respectively. CONCLUSIONS: In summary, we observed a preference in the aberrant brain for dynamic connectivity states with different network topologic organization in patients with PS, indicating abnormal functional segregation and integration of the whole brain and confirming the imperfection of functional network connectivity in patients with PS. These findings provide new evidence for the dynamic neural mechanisms underlying clinical symptoms in patients with PS.

Structural covariance in subcortical stroke patients measured by automated MRI-based volumetry.

A network-level investigation of the volumetric changes of subcortical stroke patients is still lacking. Here, we explored the alterations of structural covariance caused by subcortical stroke with automated brain volumetry. T1-weighed brain MRI scans were obtained from 63 normal controls (NC), 46 stroke patients with infarct in left internal capsule (CI_L), 33 stroke patients with infarct in right internal capsule (CI_R). We performed automatic anatomical segmentation of the T1-weighted brain images with AccuBrain. Volumetric structural covariance analyses were first performed within the basal ganglia structures that were both identified by voxel-based morphometry with AAL atlas and AccuBrain. Subsequently, we additionally included the infratentorial regions that were particularly quantified by AccuBrain for the structural covariance analyses and investigated the alterations of anatomical connections within these subcortical regions in CI_L and CI_R compared with NC. The association between the regional brain volumetry and motor function was also evaluated in stroke groups. There were significant and extensive volumetric differences in stroke patients. These significant regions were generally symmetric for CI_L and CI_R group depending on the side of stroke, involving both regions close to lesions and remote regions. The structural covariance analyses revealed the synergy volume alteration in subcortical regions both in CI_L and CI_R group. In addition, the alterations of volumetric structural covariance were more extensive in CI_L group than CI_R group. Moreover, we found that the subcortical regions with atrophy contributed to the deficits of motor function in CI_R group but not CI_L group, indicating a lesion-side effect of brain volumetric changes after stroke. These findings indicated that the chronic subcortical stroke patients have extensive disordered anatomical connections involving the whole-brain level network, and the connections patterns depend on the lesion-side.

Cerebral blood flow features in chronic subcortical stroke: Lesion location-dependent study.

We investigated the influence of lesion location on cerebral blood flow (CBF) in chronic subcortical stroke patients. Three-dimensional pseudocontinuous arterial spin labeling was employed to obtain CBF images in normal controls (NC) and patients with left hemisphere subcortical infarctions involving motor pathways. Stroke patients were divided into two subgroups based on the infarction location (basal ganglia (BS) or pontine (PS). We mapped CBF alterations in a voxel-wise manner and compared them to detect differences among groups with height-level false discovery rate correction. Regions with significant group differences were extracted to perform post hoc analyses among the BS, PS and NC groups using a general linear model with age, gender, years of education, and interval after stroke as covariates. The BS group displayed significantly increased CBF in the contralesional putamen relative to NC and significantly decreased CBF in the ipsilesional sensorimotor cortex, ipsilesional thalamus and contralesional cerebellum. The PS group displayed significantly increased CBF in the contralesional inferior frontal gyrus relative to both the NC and BS groups. Nevertheless, the PS group showed significantly decreased CBF mainly in the cerebellum. Our results suggest different alteration patterns of CBF in chronic stroke patients with different infarct locations within subcortical motor pathways, potentially providing important information for the initiation of individualized rehabilitation strategies for subcortical stroke patients involving different infarct types.

Altered gray matter volume, cerebral blood flow and functional connectivity in chronic stroke patients.

It is entangled connections and intensive functional interactions between cortex and subcortical structures that enable our brain to perform delicate movement, and poses plasticity to recover from stroke. However, it is still unclear how cortical structures and functions change in well-recovered patients from subcortical infarctions in motor pathway. In order to reveal neuroplasticity underlying well-recovered stroke patients, both structural (gray matter volume, GMV) and functional reorganizations (cerebral blood flow, CBF and resting-state functional connectivity, rsFC) were investigated by using multi-modal MRI. Our results showed that well-recovered stroke patients exhibited significantly increased GMV in contralesional supplementary motor area (SMA), increased CBFs in contralesional superior frontal gyrus (SFG) and supramarginal gyrus (SMG) irrespective of GMV correction. Furthermore, our results showed increased rsFC between contralesional middle temporal gyrus (MTG) and SMG. Negative correlations between CBF increases and behavior test scores were also observed, suggesting neural mechanism underlying clinical improvement. Our results suggested that neuroplasticity after chronic stroke showed in both structural and functional levels, and correlation between CBF change and clinical test suggested possible biomarker for stroke recovery.

Structural Alterations in Chronic Capsular versus Pontine Stroke.

Purpose To investigate whether patients with capsular stroke (CS) and patients with pontine stroke (PS) involving the motor pathway have different types of structural damage and reorganization. Materials and Methods With institutional review board approval and after obtaining written informed consent, structural magnetic resonance imaging data were prospectively acquired in 115 patients with CS, 47 patients with PS, and 116 control subjects by using four imagers from three hospitals. Patients with stroke lesions in the left and right hemispheres were analyzed (timing of follow-up imaging: mean, 597 days; range, 180-2070 days). The gray matter volume (GMV) of each voxel was compared among the three groups while controlling for the effects of age, sex, and imager. Multiple comparisons were corrected by using a false discovery rate method for voxel-wise comparisons and by using the Bonferroni method for post hoc comparisons. Results Both patients with CS and patients with PS exhibited a GMV reduction (6.18%-8.23%) in the ipsilesional anterior insular cortex and a GMV increase (5.11%-11.73%) in the supplementary motor area relative to control subjects (P < .0013). Moreover, a GMV reduction was observed in the ipsilesional sensorimotor cortex in all patients with CS (9.73%-10.41%) and in the cerebellum in all patients with PS (10.58%-15.81%). Additionally, a GMV increase was found in the precuneus in patients with PS with left lesions (17.23%) and in the middle frontal gyrus in patients with CS with right lesions (10.95%). Conclusion The different patterns of structural damage and reorganization in patients with CS versus those with PS may provide useful information in designing individualized rehabilitative strategies for these patients. © RSNA, 2017 Online supplemental material is available for this article.