Atrophy of spared gray matter tissue predicts poorer motor recovery and rehabilitation response in chronic stroke

Measuring Neuroplasticity in Response to Cardiovascular Exercise in People With Stroke: A Critical Perspective

BACKGROUND

Rehabilitative treatments that promote neuroplasticity are believed to improve recovery after stroke. Animal studies have shown that cardiovascular exercise (CE) promotes neuroplasticity but the effects of this intervention on the human brain and its implications for the functional recovery of patients remain unclear. The use of biomarkers has enabled the assessment of cellular and molecular events that occur in the central nervous system after brain injury. Some of these biomarkers have proven to be particularly valuable for the diagnosis of severity, prognosis of recovery, as well as for measuring the neuroplastic response to different treatments after stroke.

OBJECTIVES

To provide a critical analysis on the current evidence supporting the use of neurophysiological, neuroimaging, and blood biomarkers to assess the neuroplastic response to CE in individuals poststroke.

RESULTS

Most biomarkers used are responsive to the effects of acute and chronic CE interventions, but the response appears to be variable and is not consistently associated with functional improvements. Small sample sizes, methodological variability, incomplete information regarding patient's characteristics, inadequate standardization of training parameters, and lack of reporting of associations with functional outcomes preclude the quantification of the neuroplastic effects of CE poststroke using biomarkers.

CONCLUSION

Consensus on the optimal biomarkers to monitor the neuroplastic response to CE is currently lacking. By addressing critical methodological issues, future studies could advance our understanding of the use of biomarkers to measure the impact of CE on neuroplasticity and functional recovery in patients with stroke.

Functional and structural brain reorganization in patients with ischemic stroke: a multimodality MRI fusion study

Understanding how structural and functional reorganization occurs is crucial for stroke diagnosis and prognosis. Previous magnetic resonance imaging (MRI) studies focused on the analyses of a single modality and demonstrated abnormalities in both lesion regions and their associated distal regions. However, the relationships of multimodality alterations and their associations with poststroke motor deficits are still unclear. In this study, 71 hemiplegia patients and 41 matched healthy controls (HCs) were recruited and underwent MRI examination at baseline and at 2-week follow-up sessions. A multimodal fusion approach (multimodal canonical correlation analysis + joint independent component analysis), with amplitude of low-frequency fluctuation (ALFF) and gray matter volume (GMV) as features, was used to extract the co-altered patterns of brain structure and function. Then compared the changes in patients' brain structure and function between baseline and follow-up sessions. Compared with HCs, the brain structure and function of stroke patients decreased synchronously in the local lesions and their associated distal regions. Damage to structure and function in the local lesion regions was associated with motor function. After 2 weeks, ALFF in the local lesion regions was increased, while GMV did not improve. Taken together, the brain structure and function in the local lesions and their associated distal regions were damaged synchronously after ischemic stroke, while during motor recovery, the 2 modalities were changed separately.

Neuroimaging prognostic factors for treatment response to motor imagery training after stroke

The efficacy of motor imagery training for motor recovery is well acknowledged, but with substantial inter-individual variability in stroke patients. To help optimize motor imagery training therapy plans and screen suitable patients, this study aimed to explore neuroimaging biomarkers explaining variability in treatment response. Thirty-nine stroke patients were randomized to a motor imagery training group (n = 22, received a combination of conventional rehabilitation therapy and motor imagery training) and a control group (n = 17, received conventional rehabilitation therapy and health education) for 4 weeks of interventions. Their demography and clinical information, brain lesion from structural MRI, spontaneous brain activity and connectivity from rest fMRI, and sensorimotor brain activation from passive motor task fMRI were acquired to identify prognostic factors. We found that the variability of outcomes from sole conventional rehabilitation therapy could be explained by the reserved sensorimotor neural function, whereas the variability of outcomes from motor imagery training + conventional rehabilitation therapy was related to the spontaneous activity in the ipsilesional inferior parietal lobule and the local connectivity in the contralesional supplementary motor area. The results suggest that additional motor imagery training treatment is also efficient for severe patients with damaged sensorimotor neural function, but might be more effective for patients with impaired motor planning and reserved motor imagery.

Cortical thickness of contralesional cortices positively relates to future outcome after severe stroke

Imaging studies have evidenced that contralesional cortices are involved in recovery after motor stroke. Cortical thickness (CT) analysis has proven its potential to capture the changes of cortical anatomy, which have been related to recovery and treatment gains under therapy. An open question is whether CT obtained in the acute phase after stroke might inform correlational models to explain outcome variability. Data of 38 severely impaired (median NIH Stroke Scale 9, interquartile range: 6-13) acute stroke patients of 2 independent cohorts were reanalyzed. Structural imaging data were processed via the FreeSurfer pipeline to quantify regional CT of the contralesional hemisphere. Ordinal logistic regression models were fit to relate CT to modified Rankin Scale as an established measure of global disability after 3-6 months, adjusted for the initial deficit, lesion volume, and age. The data show that CT of contralesional cortices, such as the precentral gyrus, the superior frontal sulcus, and temporal and cingulate cortices, positively relates to the outcome after stroke. This work shows that the baseline cortical anatomy of selected contralesional cortices can explain the outcome variability after severe stroke, which further contributes to the concept of structural brain reserve with respect to contralesional cortices to promote recovery.

Particle hydrogels decrease cerebral atrophy and attenuate astrocyte and microglia/macrophage reactivity after stroke

Increasing numbers of individuals live with stroke related disabilities. Following stroke, highly reactive astrocytes and pro-inflammatory microglia can release cytokines and lead to a cytotoxic environment that causes further brain damage and prevents endogenous repair. Paradoxically, these same cells also activate pro-repair mechanisms that contribute to endogenous repair and brain plasticity. Here, we show that the direct injection of a hyaluronic acid based microporous annealed particle (MAP) hydrogel into the stroke core in mice reduces the percent of highly reactive astrocytes, increases the percent of alternatively activated microglia, decreases cerebral atrophy and preserves NF200 axonal bundles. Further, we show that MAP hydrogel promotes reparative astrocyte infiltration into the lesion, which directly coincides with axonal penetration into the lesion. This work shows that the injection of a porous scaffold into the stroke core can lead to clinically relevant decrease in cerebral atrophy and modulates astrocytes and microglia towards a pro-repair phenotype.

Baseline Predictors of Response to Repetitive Task Practice in Chronic Stroke

BACKGROUND

Repetitive task practice reduces mean upper extremity motor impairment in populations of patients with chronic stroke, but individual response is highly variable. A method to predict meaningful reduction in impairment in response to training based on biomarkers and other data collected prior to an intervention is needed to establish realistic rehabilitation goals and to effectively allocate resources.

OBJECTIVES

To identify prognostic factors and better understand the biological substrate for reductions in arm impairment in response to repetitive task practice among patients with chronic (≥6 months) post-stroke hemiparesis.

METHODS

The intervention is a form of repetitive task practice using a combination of robot-assisted therapy and functional arm use in real-world tasks. Baseline measures include the Fugl-Meyer Assessment, Wolf Motor Function Test, Action Research Arm Test, Stroke Impact Scale, questionnaires on pain and expectancy, MRI, transcranial magnetic stimulation, kinematics, accelerometry, and genomic testing.

RESULTS

Mean increase in FM-UE was 4.6 ± 1.0 SE, median 2.5. Approximately one-third of participants had a clinically meaningful response to the intervention, defined as an increase in FM ≥ 5. The selected logistic regression model had a receiver operating curve with AUC = .988 (Std Error = .011, 95% Wald confidence limits: .967-1) showed little evidence of overfitting. Six variables that predicted response represented impairment, functional, and genomic measures.

CONCLUSION

A simple weighted sum of 6 baseline factors can accurately predict clinically meaningful impairment reduction after outpatient intensive practice intervention in chronic stroke. Reduction of impairment may be a critical first step to functional improvement. Further validation and generalization of this model will increase its utility in clinical decision-making.

Relationship Between Cortical Excitability Changes and Cortical Thickness in Subcortical Chronic Stroke

Ischemic stroke leads to excitability changes of the motor network as probed by means of transcranial magnetic stimulation (TMS). There is still limited data that shows to what extent structural alterations of the motor network might be linked to excitability changes. Previous results argue that the microstructural state of specific corticofugal motor tracts such as the corticospinal tract associate with cortical excitability in chronic stroke patients. The relationship between changes of cortical anatomy after stroke, as operationalized by means of decreases or increases in local cortical thickness (CT), has scarcely been addressed. In the present study, we re-analyzed TMS data and recruitment curve properties of motor evoked potentials and CT data in a group of 14 well-recovered chronic stroke patients with isolated supratentorial subcortical lesions. CT data of the stroke patients were compared to CT data of 17 healthy controls. Whole-brain and region-of-interest based analyses were conducted to relate CT data to measures of motor cortical excitability and clinical data. We found that stroke patients exhibited significantly reduced CT not only in the ipsilesional primary motor cortex but also in numerous secondary motor and non-motor brain regions, particularly in the ipsilesional hemisphere including areas along the central sulcus, the inferior frontal sulcus, the intraparietal sulcus, and cingulate cortices. We could not detect any significant relationship between the extent of CT reduction and stroke-related excitability changes of the motor network or clinical scores.

Genetic Factors, Brain Atrophy, and Response to Rehabilitation Therapy After Stroke

OBJECTIVE

Patients show substantial differences in response to rehabilitation therapy after stroke. We hypothesized that specific genetic profiles might explain some of this variance and, secondarily, that genetic factors are related to cerebral atrophy post-stroke.

METHODS

The phase 3 ICARE study examined response to motor rehabilitation therapies. In 216 ICARE enrollees, DNA was analyzed for presence of the BDNF val⁶⁶met and the ApoE ε4 polymorphism. The relationship of polymorphism status to 12-month change in motor status (Wolf Motor Function Test, WMFT) was examined. Neuroimaging data were also evaluated (n=127).

RESULTS

Subjects were 61±13 years old (mean±SD) and enrolled 43±22 days post-stroke; 19.7% were BDNF val⁶⁶met carriers and 29.8% ApoE ε4 carriers. Carrier status for each polymorphism was not associated with WMFT, either at baseline or over 12 months of follow-up. Neuroimaging, acquired 5±11 days post-stroke, showed that BDNF val⁶⁶met polymorphism carriers had a 1.34-greater degree of cerebral atrophy compared to non-carriers (P=.01). Post hoc analysis found that age of stroke onset was 4.6 years younger in subjects with the ApoE ε4 polymorphism (P=.02).

CONCLUSION

Neither the val⁶⁶met BDNF nor ApoE ε4 polymorphism explained inter-subject differences in response to rehabilitation therapy. The BDNF val⁶⁶met polymorphism was associated with cerebral atrophy at baseline, echoing findings in healthy subjects, and suggesting an endophenotype. The ApoE ε4 polymorphism was associated with younger age at stroke onset, echoing findings in Alzheimer's disease and suggesting a common biology. Genetic associations provide insights useful to understanding the biology of outcomes after stroke.

Cortical Thickness of Brain Areas Beyond Stroke Lesions and Sensory-Motor Recovery: A Systematic Review

Background: The clinical outcome of patients suffering from stroke is dependent on multiple factors. The features of the lesion itself play an important role but clinical recovery is remarkably influenced by the plasticity mechanisms triggered by the stroke and occurring at a distance from the lesion. The latter translate into functional and structural changes of which cortical thickness might be easy to quantify one of the main players. However, studies on the changes of cortical thickness in brain areas beyond stroke lesion and their relationship to sensory-motor recovery are sparse. Objectives: To evaluate the effects of cerebral stroke on cortical thickness (CT) beyond the stroke lesion and its association with sensory-motor recovery. Materials and Methods: Five electronic databases (PubMed, Embase, Web of Science, Scopus and the Cochrane Library) were searched. Methodological quality of the included studies was assessed with the Newcastle-Ottawa Scale for non-randomized controlled trials and the Risk of Bias Cochrane tool for randomized controlled trials. Results: The search strategy retrieved 821 records, 12 studies were included and risk of bias assessed. In most of the included studies, cortical thinning was seen at the ipsilesional motor area (M1). Cortical thinning can occur beyond the stroke lesion, typically in regions anatomically connected because of anterograde degeneration. Nonetheless, studies also reported cortical thickening of regions of the unaffected hemisphere, likely related to compensatory plasticity. Some studies revealed a significant correlation between changes in cortical thickness of M1 or somatosensory (S1) cortical areas and motor function recovery. Discussion and Conclusions: Following a stroke, changes in cortical thickness occur both in regions directly connected to the stroke lesion and in contralateral hemisphere areas as well as in the cerebellum. The underlying mechanisms leading to these changes in cortical thickness are still to be fully understood and further research in the field is needed. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020200539; PROSPERO 2020, identifier: CRD42020200539.

Smaller spared subcortical nuclei are associated with worse post-stroke sensorimotor outcomes in 28 cohorts worldwide

Up to two-thirds of stroke survivors experience persistent sensorimotor impairments. Recovery relies on the integrity of spared brain areas to compensate for damaged tissue. Deep grey matter structures play a critical role in the control and regulation of sensorimotor circuits. The goal of this work is to identify associations between volumes of spared subcortical nuclei and sensorimotor behaviour at different timepoints after stroke. We pooled high-resolution T1-weighted MRI brain scans and behavioural data in 828 individuals with unilateral stroke from 28 cohorts worldwide. Cross-sectional analyses using linear mixed-effects models related post-stroke sensorimotor behaviour to non-lesioned subcortical volumes (Bonferroni-corrected, P < 0.004). We tested subacute (≤90 days) and chronic (≥180 days) stroke subgroups separately, with exploratory analyses in early stroke (≤21 days) and across all time. Sub-analyses in chronic stroke were also performed based on class of sensorimotor deficits (impairment, activity limitations) and side of lesioned hemisphere. Worse sensorimotor behaviour was associated with a smaller ipsilesional thalamic volume in both early (n = 179; d = 0.68) and subacute (n = 274, d = 0.46) stroke. In chronic stroke (n = 404), worse sensorimotor behaviour was associated with smaller ipsilesional putamen (d = 0.52) and nucleus accumbens (d = 0.39) volumes, and a larger ipsilesional lateral ventricle (d = -0.42). Worse chronic sensorimotor impairment specifically (measured by the Fugl-Meyer Assessment; n = 256) was associated with smaller ipsilesional putamen (d = 0.72) and larger lateral ventricle (d = -0.41) volumes, while several measures of activity limitations (n = 116) showed no significant relationships. In the full cohort across all time (n = 828), sensorimotor behaviour was associated with the volumes of the ipsilesional nucleus accumbens (d = 0.23), putamen (d = 0.33), thalamus (d = 0.33) and lateral ventricle (d = -0.23). We demonstrate significant relationships between post-stroke sensorimotor behaviour and reduced volumes of deep grey matter structures that were spared by stroke, which differ by time and class of sensorimotor measure. These findings provide additional insight into how different cortico-thalamo-striatal circuits support post-stroke sensorimotor outcomes.

Anatomical Increased/Decreased Changes in the Brain Area Following Individuals with Chronic Traumatic Complete Thoracic Spinal Cord Injury

OBJECTIVES

This study aimed to investigate anatomical changes in the brain following chronic complete traumatic thoracic spinal cord injury (ThSCI) using voxel-based morphometry (VBM). That is, it attempted to examine dynamic physical change following thoracic injury and the presence or absence of regions with decreased and increased changes in whole brain volume associated with change in the manner of how activities of daily living are performed.

METHODS

Twelve individuals with chronic traumatic complete ThSCI (age; 21-63 years, American Spinal Injury Association Impairment Scale; grade C-D) participated in this study. VBM was used to investigate the regions with increased volume and decreased volume in the brain in comparison with healthy control individuals.

RESULTS

Decreases in volume were noted in areas associated with motor and somatosensory functions, including the right paracentral lobule (PCL)-the primary motor sensory area for lower limbs, left dorsal premotor cortex, and left superior parietal lobule (SPL). Furthermore, increased gray matter volume was noted in the primary sensorimotor area for fingers and arms, as well as in higher sensory areas.

CONCLUSIONS

Following SCI both regions with increased volume and regions with decreased volume were present in the brain in accordance with changes in physical function. Using longitudinal observation, anatomical changes in the brain may be used to determine the rehabilitation effect by comparing present cases with cases with cervical SCI or cases with incomplete palsy.

Changes in brain morphometry after motor rehabilitation in chronic stroke

PURPOSE

Recent studies have revealed structural changes after motor rehabilitation, but its morphological changes related to upper limb motor behaviours have not been studied exhaustively. Therefore, we aimed to map the grey matter (GM) changes associated with motor rehabilitation after stroke using voxel-based morphometry (VBM), deformation-based morphometry (DBM), and surface-based morphometry (SBM).

METHODS

Forty-one patients with chronic stroke received twelve sessions of low-frequency repetitive transcranial magnetic stimulation plus intensive occupational therapy. MRI data were obtained before and after the intervention. Fugl-Meyer Assessment and Wolf Motor Function Test-Functional Ability Scale were assessed at the two-time points. We performed VBM, DBM, and SBM analyses using T1-weighted images. A correlation analysis was performed between cortical thickness in motor areas and clinical outcomes.

RESULTS

Clinical outcomes significantly improved after the intervention. VBM showed significant GM volume changes in ipsilesional and contralesional primary motor regions. DBM results demonstrated GM changes contralesionally and ipsilesionally after the intervention. SBM results showed significant cortical thickness changes in posterior visuomotor coordination, precentral, postcentral gyri of the ipsilesional hemisphere and contralesional visuomotor area after the intervention. A combination of threshold p < .05, False Discovery Rate and p < .001 (uncorrected) were considered significant. In addition, cortical thickness changes of the ipsilesional motor areas were significantly correlated with the clinical outcome changes.

CONCLUSIONS

We found GM structural changes in areas involved in motor, visuomotor and somatosensory functions after the intervention. Furthermore, our findings suggest that structural plasticity changes in chronic stroke could occur in the ipsilesional and contralesional hemispheres after motor rehabilitation.

Tele-rehabilitation of upper-extremity hemiparesis after stroke: Proof-of-concept randomized controlled trial of in-home Constraint-Induced Movement therapy

BACKGROUND

Although Constraint-Induced Movement therapy (CIMT) has been deemed efficacious for adults with persistent, mild-to-moderate, post-stroke upper-extremity hemiparesis, CIMT is not available on a widespread clinical basis. Impediments include its cost and travel to multiple therapy appointments. To overcome these barriers, we developed an automated, tele-health form of CIMT.

OBJECTIVE

Determine whether in-home, tele-health CIMT has outcomes as good as in-clinic, face-to-face CIMT in adults ≥1-year post-stroke with mild-to-moderate upper-extremity hemiparesis.

METHODS

Twenty-four stroke patients with chronic upper-arm extremity hemiparesis were randomly assigned to tele-health CIMT (Tele-AutoCITE) or in-lab CIMT. All received 35 hours of treatment. In the tele-health group, an automated, upper-extremity workstation with built-in sensors and video cameras was set-up in participants' homes. Internet-based audio-visual and data links permitted supervision of treatment by a trainer in the lab.

RESULTS

Ten patients in each group completed treatment. All twenty, on average, showed very large improvements immediately afterwards in everyday use of the more-affected arm (mean change on Motor Activity Log Arm Use scale = 2.5 points, p < 0.001, d' = 3.1). After one-year, a large improvement from baseline was still present (mean change = 1.8, p < 0.001, d' = 2). Post-treatment outcomes in the tele-health group were not inferior to those in the in-lab group. Neither were participants' perceptions of satisfaction with and difficulty of the interventions. Although everyday arm use was similar in the two groups after one-year (mean difference = -0.1, 95% CI = -1.3-1.0), reductions in the precision of the estimates of this parameter due to drop-out over follow-up did not permit ruling out that the tele-health group had an inferior long-term outcome.

CONCLUSIONS

This proof-of-concept study suggests that Tele-AutoCITE produces immediate benefits that are equivalent to those after in-lab CIMT in stroke survivors with chronic upper-arm extremity hemiparesis. Cost savings possible with this tele-health approach remain to be evaluated.

Unique behavioral strategies in visuomotor learning: Hope for the non-learner

The existence of individual differences in motor learning capability is well known but the behaviors or strategies that contribute to this variability have been vastly understudied. What performance characteristics distinguish an expert level performer from individuals who experience little to no success, those labeled non-learners? We designed a rule-based visuomotor task which requires identification (discovery) and then exploitation of specific explicit and implicit task components that requires a specific movement pattern, the task rule, for goal achievement. When participants first attempt the task, they are informed about the goal, but are naïve to the task rule. Therefore, the purpose of this experiment is to determine how acquisition of both implicit and explicit task components, the inherent elements of the task rule, reveals differing strategies associated with performance and task success. We test the hypothesis that an examination of performance will reveal sub-groups with varying levels of success. Further, for each subgroup, we expect to find a unique relationship between visual Time-in-Target feedback (a measure of success) and subsequent updating of each task component. Out of 32 non-disabled adults, we identified three distinct sub-groups: (Low Performer/Non-Learner (LP, N = 9), Moderate Performer (MP, N = 12) and High Performer (HP, N = 11)). A quantitative analysis of behavioral patterns reveals three findings: First, the LP sub-group demonstrated significantly lower task success which was associated with difficulty identifying the explicit component of the task. Second, the HP sub-group acquired the two task components in parallel over practice. Third, when both explicit and implicit component performance is plotted across sub-groups, a task component continuum emerges that seamlessly progresses from low to moderate to high performer groups. An exploratory analysis reveals that self-reported level of prior lifetime accumulation of video game and physical activity experience is a significant predictor of individual task performance (R² = 0.50). In summary, what appears to be a key distinction between varying levels of human rule-based motor learning is the process by which feedback is used to update performance of inherent elements of the task rule. Evidence of a performance continuum and limited prior experience suggests that Low Performer/Non-Learners are generally inexperienced with these kinds of tasks, although the role of genetics and other innate learning capabilities in visuomotor learning is still largely unknown. These findings provoke new research directions toward probing the differential performance strategies associated with expertise and the development of interventions aimed to convert non-learners into learners.

Neurofilament Light Chain (NfL) in Blood-A Biomarker Predicting Unfavourable Outcome in the Acute Phase and Improvement in the Late Phase after Stroke

Increased sensitivity of methods assessing the levels of neurofilament light chain (NfL), a neuron-specific intermediate filament protein, in human plasma or serum, has in recent years led to a number of studies addressing the utility of monitoring NfL in the blood of stroke patients. In this review, we discuss that elevated blood NfL levels after stroke may reflect several different neurobiological processes. In the acute and post-acute phase after stroke, high blood levels of NfL are associated with poor clinical outcome, and later on, the blood levels of NfL positively correlate with secondary neurodegeneration as assessed by MRI. Interestingly, increased blood levels of NfL in individuals who survived stroke for more than 10 months were shown to predict functional improvement in the late phase after stroke. Whereas in the acute phase after stroke the injured axons are assumed to be the main source of blood NfL, synaptic turnover and secondary neurodegeneration could be major contributors to blood NfL levels in the late phase after stroke. Elevated blood NfL levels after stroke should therefore be interpreted with caution. More studies addressing the clinical utility of blood NfL assessment in stroke patients are needed before the inclusion of NfL in the clinical workout as a useful biomarker in both the acute and the chronic phase after stroke.

Plasma neurofilament light chain levels predict improvement in late phase after stroke

BACKGROUND AND PURPOSE

Although functional recovery is most pronounced in the first 6 months after stroke, improvement is possible also in the late phase. The value of plasma neurofilament light chain (NfL), a biomarker of axonal injury and secondary neurodegeneration, was explored for the prediction of functional improvement in the late phase after stroke.

METHODS

Baseline plasma NfL levels were measured in 115 participants of a trial on the efficacy of multimodal rehabilitation in the late phase after stroke. The association between NfL levels, impairment in balance, gait and cognitive domains, and improvement 3 and 9 months later was determined.

RESULTS

Plasma NfL levels were associated with the degree of impairment in all three domains. Individuals with meaningful improvement in balance and gait capacity had higher plasma NfL levels compared with non-improvers (p = 0.001 and p = 0.018, respectively). Higher NfL levels were associated with improvement in balance (odds ratio [OR] 2.34, 95% confidence interval [CI] 1.35-4.27, p = 0.004) and gait (OR 2.27, 95% CI 1.25-4.32, p = 0.009). Elevated plasma NfL levels showed a positive predictive value for cognitive improvement, and this effect was specific for the intervention targeting the cognitive domain. The association of NfL levels with cognitive improvement withstood correction for baseline impairment, age and total years of schooling (OR 7.54, 95% CI 1.52-45.66, p = 0.018).

CONCLUSIONS

In addition to its established role as a biomarker in the acute phase, elevated circulating NfL levels may predict functional improvement in the late phase after stroke. Our results should prompt further studies into the use of plasma NfL as a biomarker in the late phase after stroke.

Principles of Neural Repair and Their Application to Stroke Recovery Trials

Neural repair is the underlying therapeutic strategy for many treatments currently under investigation to improve recovery after stroke. Repair-based therapies are distinct from acute stroke strategies: instead of salvaging threatened brain tissue, the goal is to improve behavioral outcomes on the basis of experience-dependent brain plasticity. Furthermore, timing, concomitant behavioral experiences, modality specific outcome measures, and careful patient selection are fundamental concepts for stroke recovery trials that can be deduced from principles of neural repair. Here we discuss core principles of neural repair and their implications for stroke recovery trials, highlighting related issues from key studies in humans. Research suggests a future in which neural repair therapies are personalized based on measures of brain structure and function, genetics, and lifestyle factors.

Biochemical and structural magnetic resonance imaging in chronic stroke and the relationship with upper extremity motor function

Background

Recovery of upper extremity (UE) motor function after stroke is variable from one to another due to heterogeneity of stroke pathology. Structural and biochemical magnetic resonance imaging of the primary motor cortex (M1) have been used to document reorganization of neural activity after stroke.

Objective

To assess cortical biochemical and structural causes of delayed recovery of UE motor function impairment in chronic subcortical ischemic stroke patients.

Methodology

A cross-sectional study with fifty patients were enrolled: thirty patients with chronic (> 6 months) subcortical ischemic stroke suffering from persistent UE motor function impairment (not improved group) and twenty patients with chronic subcortical ischemic stroke and improved UE motor function (improved group). We recruited a group of (16) age-matched healthy subjects. Single voxel proton magnetic resonance spectroscopy (1H-MRS) was performed to measure n-acetylaspartate (NAA) and glutamate+glutamine (Glx) ratios relative to creatine (Cr) in the precentral gyrus which represent M1of hand area in both ipsilesional and contralesional hemispheres. Brain magnetic resonance imaging (MRI) to measure precentral gyral thickness is representing the M1of hand area. UE motor function assessment is using the Fugl Meyer Assessment (FMA-UE) Scale.

Results

The current study found that ipslesional cortical thickness was significantly lower than contralesional cortical thickness among all stroke patients. Our study found that ipsilesional NAA/Cr ratio was lower than contralesional NAA/Cr among stroke patients. UE and hand motor function by FMA-UE showed highly statistically significant correlation with ipsilesional cortical thickness and ipsilesional NAA/Cr ratio, more powerful with NAA/Cr ratio.

Conclusion

We concluded that persistent motor impairment in individuals with chronic subcortical stroke may be at least in part related to ipsilesional structural and biochemical changes in motor areas remote from infarction in form of decreased cortical thickness and NAA/Cr ratio which had the strongest relationship with that impairment.

Vocal music enhances memory and language recovery after stroke: pooled results from two RCTs

Objective

Previous studies suggest that daily music listening can aid stroke recovery, but little is known about the stimulus‐dependent and neural mechanisms driving this effect. Building on neuroimaging evidence that vocal music engages extensive and bilateral networks in the brain, we sought to determine if it would be more effective for enhancing cognitive and language recovery and neuroplasticity than instrumental music or speech after stroke.

Methods

Using data pooled from two single‐blind randomized controlled trials in stroke patients (N = 83), we compared the effects of daily listening to self‐selected vocal music, instrumental music, and audiobooks during the first 3 poststroke months. Outcome measures comprised neuropsychological tests of verbal memory (primary outcome), language, and attention and a mood questionnaire performed at acute, 3‐month, and 6‐month stages and structural and functional MRI at acute and 6‐month stages.

Results

Listening to vocal music enhanced verbal memory recovery more than instrumental music or audiobooks and language recovery more than audiobooks, especially in aphasic patients. Voxel‐based morphometry and resting‐state and task‐based fMRI results showed that vocal music listening selectively increased gray matter volume in left temporal areas and functional connectivity in the default mode network.

Interpretation

Vocal music listening is an effective and easily applicable tool to support cognitive recovery after stroke as well as to enhance early language recovery in aphasia. The rehabilitative effects of vocal music are driven by both structural and functional plasticity changes in temporoparietal networks crucial for emotional processing, language, and memory.

Patterns of motor recovery and structural neuroplasticity after basal ganglia infarcts

OBJECTIVE

To elucidate the timeframe and spatial patterns of cortical reorganization after different stroke-induced basal ganglia lesions, we measured cortical thickness at 5 time points over a 6-month period. We hypothesized that cortical reorganization would occur very early and that, along with motor recovery, it would vary based on the stroke lesion site.

METHODS

Thirty-three patients with unilateral basal ganglia stroke and 23 healthy control participants underwent MRI scanning and behavioral testing. To further decrease heterogeneity, we split patients into 2 groups according to whether or not the lesions mainly affect the striatal motor network as defined by resting-state functional connectivity. A priori measures included cortical thickness and motor outcome, as assessed with the Fugl-Meyer scale.

RESULTS

Within 14 days poststroke, cortical thickness already increased in widespread brain areas (p = 0.001), mostly in the frontal and temporal cortices rather than in the motor cortex. Critically, the 2 groups differed in the severity of motor symptoms (p = 0.03) as well as in the cerebral reorganization they exhibited over a period of 6 months (Dice overlap index = 0.16). Specifically, the frontal and temporal regions demonstrating cortical thickening showed minimal overlap between these 2 groups, indicating different patterns of reorganization.

CONCLUSIONS

Our findings underline the importance of assessing patients early and of considering individual differences, as patterns of cortical reorganization differ substantially depending on the precise location of damage and occur very soon after stroke. A better understanding of the macrostructural brain changes following stroke and their relationship with recovery may inform individualized treatment strategies.

Machine Learning Methods Predict Individual Upper-Limb Motor Impairment Following Therapy in Chronic Stroke

Background. Accurate prediction of clinical impairment in upper-extremity motor function following therapy in chronic stroke patients is a difficult task for clinicians but is key in prescribing appropriate therapeutic strategies. Machine learning is a highly promising avenue with which to improve prediction accuracy in clinical practice. Objectives. The objective was to evaluate the performance of 5 machine learning methods in predicting postintervention upper-extremity motor impairment in chronic stroke patients using demographic, clinical, neurophysiological, and imaging input variables. Methods. A total of 102 patients (female: 31%, age 61 ± 11 years) were included. The upper-extremity Fugl-Meyer Assessment (UE-FMA) was used to assess motor impairment of the upper limb before and after intervention. Elastic net (EN), support vector machines, artificial neural networks, classification and regression trees, and random forest were used to predict postintervention UE-FMA. The performances of methods were compared using cross-validated R². Results. EN performed significantly better than other methods in predicting postintervention UE-FMA using demographic and baseline clinical data (median REN2=0.91,RRF2=0.88,RANN2=0.83,RSVM2=0.79,RCART2=0.70; P < .05). Preintervention UE-FMA and the difference in motor threshold (MT) between the affected and unaffected hemispheres were the strongest predictors. The difference in MT had greater importance than the absence or presence of a motor-evoked potential (MEP) in the affected hemisphere. Conclusion. Machine learning methods may enable clinicians to accurately predict a chronic stroke patient's postintervention UE-FMA. Interhemispheric difference in the MT is an important predictor of chronic stroke patients' response to therapy and, therefore, could be included in prospective studies.

Post-stroke remodeling processes in animal models and humans

After cerebral ischemia, events like neural plasticity and tissue reorganization intervene in lesioned and non-lesioned areas of the brain. These processes are tightly related to functional improvement and successful rehabilitation in patients. Plastic remodeling in the brain is associated with limited spontaneous functional recovery in patients. Improvement depends on the initial deficit, size, nature and localization of the infarction, together with the sex and age of the patient, all of them affecting the favorable outcome of reorganization and repair of damaged areas. A better understanding of cerebral plasticity is pivotal to design effective therapeutic strategies. Experimental models and clinical studies have fueled the current understanding of the cellular and molecular processes responsible for plastic remodeling. In this review, we describe the known mechanisms, in patients and animal models, underlying cerebral reorganization and contributing to functional recovery after ischemic stroke. We also discuss the manipulations and therapies that can stimulate neural plasticity. We finally explore a new topic in the field of ischemic stroke pathophysiology, namely the brain-gut axis.

Targeted complement inhibition salvages stressed neurons and inhibits neuroinflammation after stroke in mice

Ischemic stroke results from the interruption of blood flow to the brain resulting in long-term motor and cognitive neurological deficits, and it is a leading cause of death and disability. Current interventions focus on the restoration of blood flow to limit neuronal death, but these treatments have a therapeutic window of only a few hours and do not address post-stroke cerebral inflammation. The complement system, a component of the innate immune system, is activated by natural immunoglobulin M (IgM) antibodies that recognize neoepitopes expressed in the brain after ischemic stroke. We took advantage of this recognition system to inhibit complement activation locally in the ischemic area in mice. A single chain antibody recognizing a post-ischemic neoepitope linked to a complement inhibitor (termed B4Crry) was administered systemically as a single dose after stroke and shown to specifically target the ischemic hemisphere and improve long-term motor and cognitive recovery. We show that complement opsonins guide microglial phagocytosis of stressed but salvageable neurons, and that by locally and transiently inhibiting complement deposition, B4Crry prevented phagocytosis of penumbral neurons and inhibited pathologic complement and microglial activation that otherwise persisted for several weeks after stroke. B4Crry was protective in adult, aged, male and female mice and had a therapeutic window of at least 24 hours after stroke. Furthermore, the epitope recognized by B4Crry in mice is overexpressed in the ischemic penumbra of acute stroke patients, but not in the contralateral tissue, highlighting the translational potential of this approach.

Contralateral Brain Atrophy in Conservatively Treated Primary Intracerebral Hemorrhage

BACKGROUND

In patients with intracerebral hemorrhage (ICH), brain volume loss can occur in the hemisphere ipsilateral to the hematoma. However, contralateral hemispheric volume change after ICH is not well known. The present study aimed to investigate contralateral brain volume changes in patients with ICH who had not undergone surgery.

METHODS

Of the 2213 patients with ICH admitted to our hospital between January 2010 and December 2017, 46 patients without surgical intervention were included in the present study. We measured contralateral hemispheric brain volume in the axial images of brain computed tomography at the time of ICH onset and after 12 months. We analyzed the relationship between various factors and volume changes in the contralateral hemisphere.

RESULTS

The mean change percentage between the initial and follow-up contralateral parenchyma volume was 96.84%. The average volume decreased by 3.16% (P = 0.001). Univariate and multivariate logistic regression models revealed no significant factors associated with contralateral brain volume loss. Kruskal-Wallis test and Mann-Whitney U test showed no statistical significance (P = 0.824, P = 0.122) between ICH volume groups.

CONCLUSIONS

Contralateral parenchymal volumes were significantly decreased at follow-up brain computed tomography scanning; these changes may provide important clinical information on the remote effect of focal lesion and symptoms in the course of ICH treatment. However, further investigation is required to determine the mechanisms underlying these volume changes.

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.

Motor-imagery ability and function of hemiplegic upper limb in stroke patients

Objectives

We quantitatively examined the motor‐imagery ability in stroke patients using a bimanual circle‐line coordination task (BCT) and clarified the relationship between motor‐imagery ability and motor function of hemiplegic upper limbs and the level of use of paralyzed limbs.

Methods

We enrolled 31 stroke patients. Tasks included unimanual‐line (U‐L)—drawing straight lines on the nonparalyzed side; bimanual circle‐line (B‐CL)—drawing straight lines with the nonparalyzed limb while drawing circles with the paralyzed limb; and imagery circle‐line (I‐CL)—drawing straight lines on the nonparalyzed side during imagery drawing on the paralyzed side, using a tablet personal computer. We calculated the ovalization index (OI) and motor‐imagery ability (image OI). We used the Fugl–Meyer motor assessment (FMA), amount of use (AOU), and quality of motion (QOM) of the motor activity log (MAL) as the three variables for cluster analysis and performed mediation analysis.

Results

Clusters 1 (FMA <26 points) and 2 (FMA ≥26 points) were formed. In cluster 2, we found significant associations between image OI and FMA, AOU, and QOM. When AOU and QOM were mediated between image OI and FMA, we observed no significant direct association between image OI and FMA, and a significant indirect effect of AOU and QOM.

Interpretation

In stroke patients with moderate‐to‐mild movement disorder, image OI directly affects AOU of hemiplegic upper limbs and their QOM in daily life and indirectly influences the motor functions via those parameters.

Relation of white matter hyperintensities and motor deficits in chronic stroke

BACKGROUND

Infarct size and location account for only a relatively small portion of post-stroke motor impairment, suggesting that other less obvious factors may be involved.

OBJECTIVE

Examine the relationship between white matter hyperintensity (WMH) load among other factors and upper extremity motor deficit in patients with mild to moderate chronic stroke.

METHODS

The magnetic resonance images of 28 patients were studied. WMH load was assessed as total WMH volume and WMH overlap with the corticospinal tract in the centrum semiovale. Hemiparetic arm function was measured using the Motor Activity Log (MAL) and Wolf Motor Function Test (WMFT).

RESULTS

Hierarchical multiple regression models found WMH volume predicted motor deficits in both real-world arm use (MAL;ΔR2 = 0.12, F(1, 22) = 4.73, p = 0.04) and in arm motor capacity as measured by a laboratory motor function test (WMFT;ΔR2 = 0.18, F(1, 22) = 6.32, p = 0.02) over and above age and lesion characteristics. However, these models accounted for less than half of the variance in post-stroke motor deficits.

CONCLUSION

The results suggest that WMH may be an important factor to consider in stroke-related upper extremity motor impairment. Nonetheless, the basis of the largest part of the post-stroke motor deficit remains unaccounted for by structural CNS factors. This component may be behavioral or learned, involving learned nonuse.

Molecular Communication of a Dying Neuron in Stroke

When a main artery of the brain occludes, a cellular response involving multiple cell types follows. Cells directly affected by the lack of glucose and oxygen in the neuronal core die by necrosis. In the periphery surrounding the ischemic core (the so-called penumbra) neurons, astrocytes, microglia, oligodendrocytes, pericytes, and endothelial cells react to detrimental factors such as excitotoxicity, oxidative stress, and inflammation in different ways. The fate of the neurons in this area is multifactorial, and communication between all the players is important for survival. This review focuses on the latest research relating to synaptic loss and the release of apoptotic bodies and other extracellular vesicles for cellular communication in stroke. We also point out possible treatment options related to increasing neuronal survival and regeneration in the penumbra.

Acute Complement Inhibition Potentiates Neurorehabilitation and Enhances tPA-Mediated Neuroprotection

Because complement activation in the subacute or chronic phase after stroke was recently shown to stimulate neural plasticity, we investigated how complement activation and complement inhibition in the acute phase after murine stroke interacts with subsequent rehabilitation therapy to modulate neuroinflammation and neural remodeling. We additionally investigated how complement and complement inhibition interacts with tissue plasminogen activator (tPA), the other standard of care therapy for stroke, and a U.S. Food and Drug Administration preclinical requirement for translation of an experimental stroke therapy. CR2fH, an injury site-targeted inhibitor of the alternative complement pathway, significantly reduced infarct volume, hemorrhagic transformation, and mortality and significantly improved long-term motor and cognitive performance when administered 1.5 or 24 h after middle cerebral artery occlusion. CR2fH interrupted a poststroke inflammatory process and significantly reduced inflammatory cytokine release, microglial activation, and astrocytosis. Rehabilitation alone showed mild anti-inflammatory effects, including reduced complement activation, but only improved cognitive recovery. CR2fH combined with rehabilitation significantly potentiated cognitive and motor recovery compared with either intervention alone and was associated with higher growth factor release and enhanced rehabilitation-induced neuroblast migration and axonal remodeling. Similar outcomes were seen in adult, aged, and female mice. Using a microembolic model, CR2fH administered in combination with acute tPA therapy improved overall survival and enhanced the neuroprotective effects of tPA, extending the treatment window for tPA therapy. A human counterpart of CR2fH has been shown to be safe and nonimmunogenic in humans and we have demonstrated robust deposition of C3d, the CR2fH targeting epitope, in ischemic human brains after stroke.SIGNIFICANCE STATEMENT Complement inhibition is a potential therapeutic approach for stroke, but it is not known how complement inhibition would interact with current standards of care. We show that, after murine ischemic stroke, rehabilitation alone induced mild anti-inflammatory effects and improved cognitive, but not motor recovery. However, brain-targeted and specific inhibition of the alternative complement pathway, when combined with rehabilitation, significantly potentiated cognitive and motor recovery compared with either intervention alone via mechanisms involving neuroregeneration and enhanced brain remodeling. Further, inhibiting the alternative pathway of complement significantly enhanced the neuroprotective effects of thrombolytic therapy and markedly expanded the therapeutic window for thrombolytic therapy.

Structural Plasticity in Adulthood with Motor Learning and Stroke Rehabilitation

The development of advanced noninvasive techniques to image the human brain has enabled the demonstration of structural plasticity during adulthood in response to motor learning. Understanding the basic mechanisms of structural plasticity in the context of motor learning is essential to improve motor rehabilitation in stroke patients. Here, we review and discuss the emerging evidence for motor-learning-related structural plasticity and the implications for stroke rehabilitation. In the clinical context, a few studies have started to assess the effects of rehabilitation on structural measures to understand recovery poststroke and additionally to predict intervention outcomes. Structural imaging will likely have a role in the future in providing measures that inform patient stratification for optimal outcomes.

Abnormally reduced primary motor cortex output is related to impaired hand function in chronic stroke

Stroke often involves primary motor cortex (M1) and its corticospinal projections (CST). As hand function is critically dependent on these structures, its recovery is often incomplete. The neuronal substrate supporting affected hand function is not well understood but likely involves reorganized M1 and CST of the lesioned hemisphere (M1_IL and CST_IL). We hypothesized that affected hand function in chronic stroke is related to structural and functional reorganization of M1_IL and CST_IL. We tested 18 patients with chronic ischemic stroke involving M1 or CST. Their hand function was compared with 18 age-matched healthy subjects. M1_IL thickness and CST_IL fractional anisotropy (FA) were determined with MRI and compared with measures of the other hemisphere. Transcranial magnetic stimulation (TMS) was applied to M1_IL to determine its input-output function [stimulus response curve (SRC)]. The plateau of the SRC (MEPmax), inflection point, and slope parameters of the curve were extracted. Results were compared with measures in 12 age-matched healthy controls. MEPmax of M1_IL was significantly smaller ( P = 0.02) in the patients, indicating reduced CST_IL motor output, and was correlated with impaired hand function ( P = 0.02). M1_IL thickness ( P < 0.01) and CST_IL-FA ( P < 0.01) were reduced but did not correlate with hand function. The results indicate that employed M1_IL or CST_IL structural measures do not explain the extent of impairment in hand function once M1 and CST are sufficiently functional for TMS to evoke a motor potential. Instead, impairment of hand function is best explained by the abnormally low output from M1_IL. NEW & NOTEWORTHY Hand function often remains impaired after stroke. While the critical role of the primary motor cortex (M1) and its corticospinal output (CST) for hand function has been described in the nonhuman primate stroke model, their structure and function have not been systematically evaluated for patients after stroke. We report that in chronic stroke patients with injury to M1 and/or CST an abnormally reduced M1 output is related to impaired hand function.

Greater Cortical Thickness Is Associated With Enhanced Sensory Function After Arm Rehabilitation in Chronic Stroke

Objective. Somatosensory function is critical to normal motor control. After stroke, dysfunction of the sensory systems prevents normal motor function and degrades quality of life. Structural neuroplasticity underpinnings of sensory recovery after stroke are not fully understood. The objective of this study was to identify changes in bilateral cortical thickness (CT) that may drive recovery of sensory acuity. Methods. Chronic stroke survivors (n = 20) were treated with 12 weeks of rehabilitation. Measures were sensory acuity (monofilament), Fugl-Meyer upper limb and CT change. Permutation-based general linear regression modeling identified cortical regions in which change in CT was associated with change in sensory acuity. Results. For the ipsilesional hemisphere in response to treatment, CT increase was significantly associated with sensory improvement in the area encompassing the occipital pole, lateral occipital cortex (inferior and superior divisions), intracalcarine cortex, cuneal cortex, precuneus cortex, inferior temporal gyrus, occipital fusiform gyrus, supracalcarine cortex, and temporal occipital fusiform cortex. For the contralesional hemisphere, increased CT was associated with improved sensory acuity within the posterior parietal cortex that included supramarginal and angular gyri. Following upper limb therapy, monofilament test score changed from 45.0 ± 13.3 to 42.6 ± 12.9 mm ( P = .063) and Fugl-Meyer score changed from 22.1 ± 7.8 to 32.3 ± 10.1 ( P < .001). Conclusions. Rehabilitation in the chronic stage after stroke produced structural brain changes that were strongly associated with enhanced sensory acuity. Improved sensory perception was associated with increased CT in bilateral high-order association sensory cortices reflecting the complex nature of sensory function and recovery in response to rehabilitation.

Correlation of Longitudinal Gray Matter Volume Changes and Motor Recovery in Patients After Pontine Infarction

The mechanisms of motor functional recovery after pontine infarction (PI) remain unclear. Here, we assessed longitudinal changes in gray matter volume (GMV) and examined the relationship between GMV and clinical outcome. Fifteen patients with unilateral PI underwent magnetic resonance imaging and neurological exams five times during a period of 6 months. Another 15 healthy participants were enrolled as the normal control (NC) group and were examined with the same protocol. The MR exam included routine protocol and a 3D T1-weighted magnetization-prepared rapid acquisition gradient echo scan. Changes in GMV were assessed using voxel-based morphometry. Furthermore, the correlations between GMV changes in regions of interest and clinical scores were assessed. Compared with NCs, the decreased GMVs in the contralateral uvula of cerebellum and the ipsilateral tuber of cerebellum were detected at third month after stroke onset. At the sixth month after stroke onset, the decreased GMVs were detected in the contralateral culmen of cerebellum, putamen, as well as in the ipsilateral tuber/tonsil of cerebellum. Compared with NC, the PI group exhibited significant increases in GMV at each follow-up time point relative to stroke onset. Specifically, the significant GMV increase was found in the ipsilateral middle frontal gyrus and ventral anterior nucleus of thalamus at second week after stroke onset. At first month after stroke onset, the increased GMVs in the ipsilateral middle temporal gyrus were detected. The significant GMV increase in the ipsilateral mediodorsal thalamus was noted at third month after stroke onset. At the end of sixth month after stroke onset, the GMV increase was found in the ipsilateral mediodorsal thalamus, superior frontal gyrus, and the contralateral precuneus. Across five times during a period of 6-month, a negative correlation was observed between mean GMV in the contralateral uvula, culmen, putamen, and ipsilateral tuber/tonsil and mean Fugl-Meyer (FM) score. However, mean GMV in the ipsilateral mediodorsal thalamus was positively correlated with mean FM score. Our findings suggest that structural reorganization of the ipsilateral mediodorsal thalamus might contribute to motor functional recovery after PI.

Type-2 diabetes mellitus reduces cortical thickness and decreases oxidative metabolism in sensorimotor regions after stroke

Individuals with type-2 diabetes mellitus experience poor motor outcomes after ischemic stroke. Recent research suggests that type-2 diabetes adversely impacts neuronal integrity and function, yet little work has considered how these neuronal changes affect sensorimotor outcomes after stroke. Here, we considered how type-2 diabetes impacted the structural and metabolic function of the sensorimotor cortex after stroke using volumetric magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS). We hypothesized that the combination of chronic stroke and type-2 diabetes would negatively impact the integrity of sensorimotor cortex as compared to individuals with chronic stroke alone. Compared to stroke alone, individuals with stroke and diabetes had lower cortical thickness bilaterally in the primary somatosensory cortex, and primary and secondary motor cortices. Individuals with stroke and diabetes also showed reduced creatine levels bilaterally in the sensorimotor cortex. Contralesional primary and secondary motor cortex thicknesses were negatively related to sensorimotor outcomes in the paretic upper-limb in the stroke and diabetes group such that those with thinner primary and secondary motor cortices had better motor function. These data suggest that type-2 diabetes alters cerebral energy metabolism, and is associated with thinning of sensorimotor cortex after stroke. These factors may influence motor outcomes after stroke.

Rehabilitation of stroke patients with plegic hands: Randomized controlled trial of expanded Constraint-Induced Movement therapy

PURPOSE

To evaluate the efficacy of an expanded form of Constraint-Induced Movement Therapy (eCIMT) that renders CIMT, originally designed for treating mild-to-moderate upper-extremity hemiparesis, suitable for treating severe hemiparesis.

METHODS

Twenty-one adults ≥1 year after stroke with severe upper-extremity hemiparesis (with little or no capacity to make movements with the more-affected hand) were randomly assigned to eCIMT (n = 10), a placebo-control procedure (n = 4), or usual care (n = 7). The participants who received usual care were crossed over to eCIMT four months after enrollment. The CIMT protocol was altered to include fitting of orthotics and adaptive equipment, selected neurodevelopmental techniques, and electromyography-triggered functional electrical stimulation. Treatment was given for 15 consecutive weekdays with 6 hours of therapy scheduled daily for the immediate eCIMT group and 3.5 hours daily for the cross-over eCIMT group.

RESULTS

At post-treatment, the immediate eCIMT group showed significant gains relative to the combination of the control groups on the Grade-4/5 Motor Activity Log (MAL; mean = 1.5 points, P < 0.001, f = 4.2) and a convergent measure, the Canadian Occupational Performance Measure (COPM; mean = 2.3, P = 0.014, f = 1.1; f values ≥0.4 are considered large, on the COPM changes ≥2 are considered clinically meaningful). At 1-year follow-up, the MAL gains in the immediate eCIMT group were only 13% less than at post-treatment. The short and long-term outcomes of the crossover eCIMT group were similar to those of the immediate eCIMT group.

CONCLUSIONS

This small, randomized controlled trial (RCT) suggests that eCIMT produces a large, meaningful, and persistent improvement in everyday use of the more-affected arm in adults with severe upper-extremity hemiparesis long after stroke. These promising findings warrant confirmation by a large RCT.

Cortical thickness and metabolite concentration in chronic stroke and the relationship with motor function

BACKGROUND

Hemiparesis is one of the most prevalent chronic disabilities after stroke. Biochemical and structural magnetic resonance imaging approaches may be employed to study the neural substrates underpinning upper-extremity (UE) recovery after chronic stroke.

OBJECTIVE

The purposes of this study were to 1) quantify anatomical and metabolic differences in the precentral gyrus, and 2) test the relationships between anatomical and metabolic differences, and hemiparetic arm function in individuals in the chronic stage of stroke recovery. Our hypotheses were: 1) the Stroke group would exhibit reduced precentral gyrus cortical thickness and lower concentrations of total N-acetylaspartate (tNAA) and glutamate+glutamine (Glx) in the ipsilesional motor cortex; and 2) that each of these measures would be associated with UE motor function after stroke.

METHODS

Seventeen individuals with chronic (>6 months) subcortical ischemic stroke and eleven neurologically healthy controls were recruited. Single voxel proton magnetic resonance spectroscopy (H1MRS) was performed to measure metabolite concentrations of tNAA and Glx in the precentral gyrus in both ipsilesional and contralesional hemispheres. Surface-based cortical morphometry was used to quantify precentral gyral thickness. Upper-extremity motor function was assessed using the Wolf Motor Function Test (WMFT).

RESULTS

Results demonstrated significantly lower ipsilesional tNAA and Glx concentrations and precentral gyrus thickness in the Stroke group. Ipsilesional tNAA and Glx concentration and precentral gyrus thickness was significantly lower in the ipsilesional hemisphere in the Stroke group. Parametric correlation analyses revealed a significant positive relationship between precentral gyrus thickness and tNAA concentration bilaterally. Multivariate regression analyses revealed that ipsilesional concentrations of tNAA and Glx predicted the largest amount of variance in WMFT scores. Cortical thickness measures alone did not predict a significant amount of variance in WMFT scores.

CONCLUSION

While stroke impairs both structure and biochemistry in the ipsilesional hemisphere our data suggest that tNAA has the strongest relationship with motor function.

Transient Ischemic Attack Results in Delayed Brain Atrophy and Cognitive Decline

BACKGROUND AND PURPOSE

Transient ischemic attack (TIA) initiates an ischemic cascade without resulting in frank infarction and, as such, represents a novel model to study the effects of this ischemic cascade and secondary neurodegeneration in humans.

METHODS

Patients with suspected TIA underwent acute brain perfusion imaging, and those with acute ischemia were enrolled into a prospective observational study. We collected baseline and 90-day magnetic resonance imaging, including MP-RAGE (high-resolution T1 sequence) and cognitive assessment with the Montreal Cognitive Assessment. Brain morphometry and within patient statistical analysis were performed to identify changes between baseline and 90-day imaging and clinical assessments.

RESULTS

Fifty patients with TIA with acute perfusion lesions were studied. All patients experienced a decrease in global cortical gray matter (P=0.005). Patients with anterior circulation TIA (n=31) also had a significant reduction in the volume of the pons (P<0.001), ipsilesional parietal lobe (P<0.001), occipital lobe (P=0.002), frontal lobe (P<0.001), temporal lobe (P=0.003), and thalamus (P=0.016). Patients with an anterior perfusion lesion on acute imaging also had a significant decrease in Montreal Cognitive Assessment between baseline and day 90 (P=0.027), which may be related to the volume of thalamic atrophy (R²=0.28; P=0.009).

CONCLUSIONS

In a prospective observational study, patients with TIA confirmed by acute perfusion imaging experienced a significant reduction in global gray matter and focal structural atrophy related to the area of acute ischemia. The atrophy also resulted in a proportional decreased cognitive performance on the Montreal Cognitive Assessment. Further studies are required to identify the mechanisms of this atrophy.

Treatments to Promote Neural Repair after Stroke

Stroke remains a major cause of human disability worldwide. In parallel with advances in acute stroke interventions, new therapies are under development that target restorative processes. Such therapies have a treatment time window measured in days, weeks, or longer and so have the advantage that they may be accessible by a majority of patients. Several categories of restorative therapy have been studied and are reviewed herein, including drugs, growth factors, monoclonal antibodies, activity-related therapies including telerehabilitation, and a host of devices such as those related to brain stimulation or robotics. Many patients with stroke do not receive acute stroke therapies or receive them and do not derive benefit, often surviving for years thereafter. Therapies based on neural repair hold the promise of providing additional treatment options to a majority of patients with stroke.

Functional Activation-Informed Structural Changes during Stroke Recovery: A Longitudinal MRI Study

Objective

Neuroimaging studies revealed the functional reorganization or the structural changes during stroke recovery. However, previous studies did not combine the functional and structural information and the results might be affected by heterogeneous lesion. This study aimed to investigate functional activation-informed structural changes during stroke recovery.

Methods

MRI data of twelve stroke patients were collected at four consecutive time points during the first 3 months after stroke onset. Functional activation during finger-tapping task was used to inform the analysis of structural changes of activated brain regions. Correlation between structural changes in motor-related activated brain regions and motor function recovery was estimated.

Results

The averaged gray matter volume (aGMV) of contralesional activated brain regions and laterality index of gray matter volume (LI_GMV) increased during stroke recovery, and LI_GMV was positively correlated with Fugl-Meyer Index (FMI) at initial stage after stroke. The aGMV of bilateral activated brain regions was negatively correlated with FMI during the stroke recovery.

Conclusion

This study demonstrated that combining the stroke-induced functional reorganization and structural change provided new insights into the underlying innate plasticity process during stroke recovery.

Significance

This study proposed a new approach to integrate functional and structural information for investigating the innate plasticity after stroke.

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.

Right Hemisphere Grey Matter Volume and Language Functions in Stroke Aphasia

The role of the right hemisphere (RH) in recovery from aphasia is incompletely understood. The present study quantified RH grey matter (GM) volume in individuals with chronic stroke-induced aphasia and cognitively healthy people using voxel-based morphometry. We compared group differences in GM volume in the entire RH and in RH regions-of-interest. Given that lesion site is a critical source of heterogeneity associated with poststroke language ability, we used voxel-based lesion symptom mapping (VLSM) to examine the relation between lesion site and language performance in the aphasic participants. Finally, using results derived from the VLSM as a covariate, we evaluated the relation between GM volume in the RH and language ability across domains, including comprehension and production processes both at the word and sentence levels and across spoken and written modalities. Between-subject comparisons showed that GM volume in the RH SMA was reduced in the aphasic group compared to the healthy controls. We also found that, for the aphasic group, increased RH volume in the MTG and the SMA was associated with better language comprehension and production scores, respectively. These data suggest that the RH may support functions previously performed by LH regions and have important implications for understanding poststroke reorganization.

The impact of large structural brain changes in chronic stroke patients on the electric field caused by transcranial brain stimulation

Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (TDCS) are two types of non-invasive transcranial brain stimulation (TBS). They are useful tools for stroke research and may be potential adjunct therapies for functional recovery. However, stroke often causes large cerebral lesions, which are commonly accompanied by a secondary enlargement of the ventricles and atrophy. These structural alterations substantially change the conductivity distribution inside the head, which may have potentially important consequences for both brain stimulation methods. We therefore aimed to characterize the impact of these changes on the spatial distribution of the electric field generated by both TBS methods. In addition to confirming the safety of TBS in the presence of large stroke-related structural changes, our aim was to clarify whether targeted stimulation is still possible. Realistic head models containing large cortical and subcortical stroke lesions in the right parietal cortex were created using MR images of two patients. For TMS, the electric field of a double coil was simulated using the finite-element method. Systematic variations of the coil position relative to the lesion were tested. For TDCS, the finite-element method was used to simulate a standard approach with two electrode pads, and the position of one electrode was systematically varied. For both TMS and TDCS, the lesion caused electric field "hot spots" in the cortex. However, these maxima were not substantially stronger than those seen in a healthy control. The electric field pattern induced by TMS was not substantially changed by the lesions. However, the average field strength generated by TDCS was substantially decreased. This effect occurred for both head models and even when both electrodes were distant to the lesion, caused by increased current shunting through the lesion and enlarged ventricles. Judging from the similar peak field strengths compared to the healthy control, both TBS methods are safe in patients with large brain lesions (in practice, however, additional factors such as potentially lowered thresholds for seizure-induction have to be considered). Focused stimulation by TMS seems to be possible, but standard tDCS protocols appear to be less efficient than they are in healthy subjects, strongly suggesting that tDCS studies in this population might benefit from individualized treatment planning based on realistic field calculations.

Exercise in the Early Stage after Stroke Enhances Hippocampal Brain-Derived Neurotrophic Factor Expression and Memory Function Recovery

BACKGROUND

Exercise in the early stage after stroke onset has been shown to facilitate the recovery from physical dysfunction. However, the mechanism of recovery has not been clarified. In this study, the effect of exercise on spatial memory function recovery in the early stage was shown, and the mechanism of recovery was discussed using a rat model of brain embolism.

METHODS

Intra-arterial microsphere (MS) injection induced small emboli in the rat brain. Treadmill exercise was started at 24 hours (early group) or 8 days (late group) after MS injection. The non-exercise (NE) and sham-operated groups were included as controls. Memory function was evaluated by the Morris water maze test, and hippocampal levels of brain-derived neurotrophic factor (BDNF) were measured by enzyme-linked immunosorbent assays. To further investigate the effect of BDNF on memory function, BDNF was continuously infused into the hippocampus via implantable osmotic pumps in the early or late stage after stroke.

RESULTS

Memory function significantly improved only in the early group compared with the late and the NE groups, although hippocampal BDNF concentrations were temporarily elevated after exercise in both the early and the late groups. Rats infused with BDNF in the early stage exhibited significant memory function recovery; however, rats that received BDNF infusion in the late stage showed no improvement.

CONCLUSION

Exercise elevates hippocampal BDNF levels in the early stage after cerebral embolism, and this event facilitates memory function recovery.

Regional brain structural abnormality in ischemic stroke patients: a voxel-based morphometry study

Our previous study used regional homogeneity analysis and found that activity in some brain areas of patients with ischemic stroke changed significantly. In the current study, we examined structural changes in these brain regions by taking structural magnetic resonance imaging scans of 11 ischemic stroke patients and 15 healthy participants, and analyzing the data using voxel-based morphometry. Compared with healthy participants, patients exhibited higher gray matter density in the left inferior occipital gyrus and right anterior white matter tract. In contrast, gray matter density in the right cerebellum, left precentral gyrus, right middle frontal gyrus, and left middle temporal gyrus was less in ischemic stroke patients. The changes of gray matter density in the middle frontal gyrus were negatively associated with the clinical rating scales of the Fugl-Meyer Motor Assessment (r = -0.609, P = 0.047) and the left middle temporal gyrus was negatively correlated with the clinical rating scales of the nervous functional deficiency scale (r = -0.737, P = 0.010). Our findings can objectively identify the functional abnormality in some brain regions of ischemic stroke patients.