Long-Term Deficits in Episodic Memory after Ischemic Stroke: Evaluation and Prediction of Verbal and Visual Memory Performance Based on Lesion Characteristics

MRI factors associated with cognitive functioning after acute onset brain injury: Systematic review and meta-analysis

Impairments of memory, attention, and executive functioning are frequently reported after acute onset brain injury. MRI markers hold potential to contribute to identification of patients at risk for cognitive impairments and clarification of mechanisms. The aim of this systematic review was to summarize and value the evidence on MRI markers of memory, attention, and executive functioning after acute onset brain injury. We included ninety-eight studies, on six classes of MRI factors (location and severity of damage (n = 15), volume/atrophy (n = 36), signs of small vessel disease (n = 15), diffusion-weighted imaging measures (n = 36), resting-state functional MRI measures (n = 13), and arterial spin labeling measures (n = 1)). Three measures showed consistent results regarding their association with cognition. Smaller hippocampal volume was associated with worse memory in fourteen studies (pooled correlation 0.58 [95% CI: 0.46-0.68] for whole, 0.11 [95% CI: 0.04-0.19] for left, and 0.34 [95% CI: 0.17-0.49] for right hippocampus). Lower fractional anisotropy in cingulum and fornix was associated with worse memory in six and five studies (pooled correlation 0.20 [95% CI: 0.08-0.32] and 0.29 [95% CI: 0.20-0.37], respectively). Lower functional connectivity within the default-mode network was associated with worse cognition in four studies. In conclusion, hippocampal volume, fractional anisotropy in cingulum and fornix, and functional connectivity within the default-mode network showed consistent associations with cognitive performance in all types of acute onset brain injury. External validation and cut off values for predicting cognitive impairments are needed for clinical implementation.

Visuospatial processing skills following unilateral arterial ischemic stroke in childhood

Due to the rare occurrence of childhood stroke, its impact on later cognitive functioning remains unclear. While it is often assumed that children recover better than adults, recent studies suggest that childhood stroke can negatively affect a wide range of cognitive domains, such as attention, language, and processing speed, among others. We examined the effect of unilateral stroke on children's visuoconstructive ability and visual memory. Seventeen children with left- or right-sided arterial ischemic stroke were tested using subtests of the Hamburg-Wechsler Intelligenztest für Kinder and the Rey-Osterrieth Complex Figure (ROCF). The ROCF was evaluated both quantitatively and qualitatively with the help of two separate scoring methods. We found that lesion laterality and age at stroke impacted childhood stroke patients' ability to recall certain elements of the figure. Regarding lesion laterality, left-sided stroke patients had more difficulties recalling internal details than right-sided stroke patients. In terms of age, patients with stroke onset before the age of 5 years remembered fewer structural elements than patients with stroke onset after the age of 5 years did. Moreover, the qualitative scoring method better differentiated between individuals and between groups than the more commonly used quantitative method. The results of this study not only highlight the importance of a qualitative assessment of the ROCF but could also aid clinicians in testing stroke patients more accurately and tailoring subsequent therapy to the patient's individual needs.

Mid-range visual functions in relation to higher-order visual functions after stroke

INTRODUCTION

We aimed to investigate whether associations between deficits in "mid-range" visual functions and deficits in higher-order visual cognitive functions in stroke patients are more in line with a hierarchical, two-pathway model of the visual brain, or with a patchwork model, which assumes a parallel organization with many processing routes and cross-talk.

METHODS

A group of 182 ischemic stroke patients was assessed with a new diagnostic set-up for the investigation of a comprehensive range of visuosensory mid-range functions: color, shape, location, orientation, correlated motion, contrast and texture. With logistic regression analyses we investigated the predictive value of these mid-range functions for deficits in visuoconstruction (Copy of the Rey-Complex Figure Test), visual emotion recognition (Ekman 60 Faces Test of the FEEST) and visual memory (computerized Doors-test).

RESULTS

Results showed that performance on most mid-range visual tasks could not predict performance on higher-order visual cognitive tasks. Correlations were low to weak. Impaired visuoconstruction and visual memory were only modestly predicted by a worse location perception. Impaired emotion perception was modestly predicted by a worse orientation perception. In addition, double dissociations were found: there were patients with selective deficits in mid-range visual functions without higher-order visual deficits and vice versa.

CONCLUSIONS

Our findings are not in line with the hierarchical, two-pathway model. Instead, the findings are more in line with alternative "patchwork" models, arguing for a parallel organization with many processing routes and cross-talk. However, future studies are needed to test these alternative models.

Accelerated Long-Term Forgetting: Prolonged Delayed Recognition as Sensitive Measurement for Different Profiles of Long-Term Memory and Metacognitive Confidence in Stroke Patients

OBJECTIVE

Deficits in episodic memory are frequently reported after ischemic stroke. In standard clinical care, episodic memory is assessed after a 20-30 min delay, with abnormal memory decay over this period being characterized as rapid forgetting (RF). Previous studies have shown abnormal forgetting over a prolonged interval (days to weeks) despite normal acquisition, referred to as accelerated long-term forgetting (ALF).

METHOD

We examined whether ALF is present in stroke patients (N = 91) using immediate testing (T1), testing after a short delay (20-30 min, T2), and testing after a prolonged delay (one week, T3). Based on performance compared to matched controls (N = 85), patients were divided into (1) patients without forgetting, (2) patients with RF between T1 and T2, and (3) patients with ALF at T3. Furthermore, confidence ratings were assessed.

RESULTS

ALF was present in a moderate amount of stroke patients (17%), but ALF was even more prevalent in our stroke sample than RF after a 20-30 min delay (which was found in only 13% of our patients). Patients reported a lower confidence for their responses, independent of their actual performance.

CONCLUSIONS

Adding a one-week delayed measurement may potentially assist in identifying patients with memory decrements that may otherwise go undetected.

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

BACKGROUND AND PURPOSE

The optimal management of post-stroke cognitive impairment (PSCI) remains controversial. These joint European Stroke Organisation (ESO) and European Academy of Neurology (EAN) guidelines provide evidence-based recommendations to assist clinicians in decision making regarding prevention, diagnosis, treatment and prognosis.

METHODS

Guidelines were developed according to the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) methodology. The working group identified relevant clinical questions, performed systematic reviews, assessed the quality of the available evidence, and made specific recommendations. Expert consensus statements were provided where insufficient evidence was available to provide recommendations.

RESULTS

There was limited randomized controlled trial (RCT) evidence regarding single or multicomponent interventions to prevent post-stroke cognitive decline. Lifestyle interventions and treating vascular risk factors have many health benefits, but a cognitive effect is not proven. We found no evidence regarding routine cognitive screening following stroke, but recognize the importance of targeted cognitive assessment. We describe the accuracy of various cognitive screening tests, but found no clearly superior approach to testing. There was insufficient evidence to make a recommendation for use of cholinesterase inhibitors, memantine nootropics or cognitive rehabilitation. There was limited evidence on the use of prediction tools for post-stroke cognition. The association between PSCI and acute structural brain imaging features was unclear, although the presence of substantial white matter hyperintensities of presumed vascular origin on brain magnetic resonance imaging may help predict cognitive outcomes.

CONCLUSIONS

These guidelines highlight fundamental areas where robust evidence is lacking. Further definitive RCTs are needed, and we suggest priority areas for future research.

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

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

Hyperbaric oxygen therapy improves neurocognitive functions of post-stroke patients - a retrospective analysis

Background:

Previous studies have shown that hyperbaric oxygen therapy (HBOT) can improve the motor functions and memory of post-stroke patients in the chronic stage.

Objective:

The aim of this study is to evaluate the effects of HBOT on overall cognitive functions of post-stroke patients in the chronic stage. The nature, type and location of the stroke were investigated as possible modifiers.

Methods:

A retrospective analysis was conducted on patients who were treated with HBOT for chronic stroke (>3 months) between 2008-2018. Participants were treated in a multi-place hyperbaric chamber with the following protocols: 40 to 60 daily sessions, 5 days per week, each session included 90 min of 100% oxygen at 2 ATA with 5 min air brakes every 20 minutes. Clinically significant improvements (CSI) were defined as > 0.5 standard deviation (SD).

Results:

The study included 162 patients (75.3% males) with a mean age of 60.75±12.91. Of them, 77(47.53%) had cortical strokes, 87(53.7%) strokes were located in the left hemisphere and 121 suffered ischemic strokes (74.6%).

HBOT induced a significant increase in all the cognitive function domains (p < 0.05), with 86% of the stroke victims achieving CSI. There were no significant differences post-HBOT of cortical strokes compared to sub-cortical strokes (p > 0.05). Hemorrhagic strokes had a significantly higher improvement in information processing speed post-HBOT (p < 0.05). Left hemisphere strokes had a higher increase in the motor domain (p < 0.05). In all cognitive domains, the baseline cognitive function was a significant predictor of CSI (p < 0.05), while stroke type, location and side were not significant predictors.

Conclusions:

HBOT induces significant improvements in all cognitive domains even in the late chronic stage. The selection of post-stroke patients for HBOT should be based on functional analysis and baseline cognitive scores rather than the stroke type, location or side of lesion.

Behavioral and Neural Correlates of Cognitive Training and Transfer Effects in Stroke Patients

Stroke lesions are frequently followed by cognitive impairments. Cognitive training is a non-pharmacological intervention that can promote neural compensation mechanisms and strategies to remediate cognitive impairments. The aims of this study were: (1) To investigate the cognitive performance, generalization effects, and neural correlates of semantic organization strategy training (SOST) in patients with chronic left frontoparietal stroke and healthy controls (HC); and (2) to compare the behavioral effects and neural correlates of SOST with an active control psychoeducation intervention (PI). In this randomized controlled study, all participants were randomly allocated into two groups, one group received SOST, and the other received PI intervention. Participants underwent two fMRI sessions, one prior and the other, after intervention. In each fMRI session, images were obtained during memory encoding task using a list of semantically related words. We found improved post-intervention memory performance in participants that received SOST (both patients and controls), indicated by number of words recalled, word clustering scores, and performance in a generalization task. The fMRI analysis revealed negative correlation between task performance and regions of the default-mode network. These results suggest that cognitive training using semantic organization strategy can improve episodic memory performance and promote potential functional neuroplasticity in patients with ischemic stroke lesions. Clinical Trial Registration: www.ClinicalTrials.gov, identifier: NCT03644290.

Ipsilateral primary motor cortex and behavioral compensation after stroke: a case series study

Arm motor recovery after stroke is mainly attributed to reorganization of the primary motor cortex (M1). While M1 contralateral to the paretic arm (cM1) is critical for recovery, the role of ipsilateral M1 (iM1) is still inconclusive. Whether iM1 activity is related to recovery, behavioral compensation, or both is still far from settled. We hypothesized that the magnitude of iM1 activity in chronic stroke survivors will increase or decrease in direct proportion to the degree that movements of the paretic arm are compensated. Movement kinematics (VICON, Oxford Metrics) and functional MRI data (3T MR system) were collected in 11 patients before and after a 4-week training designed to improve motor control of the paretic arm and decrease compensatory trunk recruitment. Twelve matched controls underwent similar evaluations and training. Relationships between iM1 activity and trunk motion were analyzed. At baseline, patients exhibited increased iM1 activity (p = 0.001) and relied more on trunk movement (p = 0.02) than controls. These two variables were directly and significantly related in patients (r = 0.74, p = 0.01) but not in controls (r = 0.28, p = 0.4). After training, patients displayed a significant reduction in iM1 activity (p = 0.008) and a trend toward decreased trunk use (p = 0.1). The relationship between these two variables remained significant (r = 0.66, p = 0.03) and different from controls (r = 0.26, p = 0.4). Our preliminary results suggest that iM1 may play a role in compensating for brain damage rather than directly gaining control of the paretic arm. However, we recommend caution in interpreting these results until more work is completed.

Regional Shape Abnormalities in Thalamus and Verbal Memory Impairment After Subcortical Infarction

Background. Subcortical infarcts can result in verbal memory impairment, but the potential underlying mechanisms remain unknown. Objective. We investigated the spatiotemporal deterioration patterns of brain structures in patients with subcortical infarction and identified the regions that contributed to verbal memory impairment. Methods. Cognitive assessment and structural magnetic resonance imaging were performed 1, 4, and 12 weeks after stroke onset in 28 left-hemisphere and 22 right-hemisphere stroke patients with subcortical infarction. Whole-brain volumetric analysis combined with a further-refined shape analysis was conducted to analyze longitudinal morphometric changes in brain structures and their relationship to verbal memory performance. Results. Between weeks 1 and 12, significant volume decreases in the ipsilesional basal ganglia, inferior white matter, and thalamus were found in the left-hemisphere stroke group. Among those 3 structures, only the change rate of the thalamus volume was significantly correlated with that in immediate recall. For the right-hemisphere stroke group, only the ipsilesional basal ganglia survived the week 1 to week 12 group comparison, but its change rate was not significantly correlated with the verbal memory change rate. Shape analysis of the thalamus revealed atrophies of the ipsilesional thalamic subregions connected to the prefrontal, temporal, and premotor cortices in the left-hemisphere stroke group and positive correlations between the rates of those atrophies and the change rate in immediate recall. Conclusions. Secondary damage to the thalamus, especially to the left subregions connected to specific cortices, may be associated with early verbal memory impairment following an acute subcortical infarct.

Intranasal cerebrolysin improves cognitive function and structural synaptic plasticity in photothrombotic mouse model of medial prefrontal cortex ischemia

Medial prefrontal cortex (mPFC) ischemia affects post-stroke cognitive outcomes. We aimed to investigate the effects of different doses and routes of cerebrolysin (CBL) on the structural synaptic plasticity and cognitive function after mPFC ischemia in mice. Thence, CBL (1, 2.5 ml/kg/i.p./daily) or (1 ml/kg/i.n./daily), were administrated in photothrombotic mouse model of mPFC ischemia for two weeks. Episodic and spatial memories were assessed by the What-Where-Which (WWWhich) and Barnes tasks. Growth-associated protein 43 (GAP-43), postsynaptic density-95 (PSD-95), and synaptophysin (SYN) levels were measured in the lesioned area using western blot analysis. Dendritic arbors, spine densities, and morphology were assessed via Golgi-Cox staining. Treatment with 2.5 ml/kg/i.p. and 1 ml/kg/i.n. doses attenuated mPFC ischemia-induced episodic and spatial memories impairment. Results showed an obvious increase in the GAP-43, PSD-95 and SYN levels and improvement in the structural synaptic indexes in lesioned area induced by the same doses and routes of CBL. In conclusion, we found that specific doses/routes of CBL have positive effects on the structural synaptic plasticity and cognitive outcomes after mPFC ischemia.

Theoretical Modeling of Cognitive Dysfunction in Schizophrenia by Means of Errors and Corresponding Brain Networks

The current evidence of cognitive disturbances and brain alterations in schizophrenia does not provide the plausible explanation of the underlying mechanisms. Neuropsychological studies outlined the cognitive profile of patients with schizophrenia, that embodied the substantial disturbances in perceptual and motor processes, spatial functions, verbal and non-verbal memory, processing speed and executive functioning. Standardized scoring in the majority of the neurocognitive tests renders the index scores or the achievement indicating the severity of the cognitive impairment rather than the actual performance by means of errors. At the same time, the quantitative evaluation may lead to the situation when two patients with the same index score of the particular cognitive test, demonstrate qualitatively different performances. This may support the view why test paradigms that habitually incorporate different cognitive variables associate weakly, reflecting an ambiguity in the interpretation of noted cognitive constructs. With minor exceptions, cognitive functions are not attributed to the localized activity but eventuate from the coordinated activity in the generally dispersed brain networks. Functional neuroimaging has progressively explored the connectivity in the brain networks in the absence of the specific task and during the task processing. The spatio-temporal fluctuations of the activity of the brain areas detected in the resting state and being highly reproducible in numerous studies, resemble the activation and communication patterns during the task performance. Relatedly, the activation in the specific brain regions oftentimes is attributed to a number of cognitive processes. Given the complex organization of the cognitive functions, it becomes crucial to designate the roles of the brain networks in relation to the specific cognitive functions. One possible approach is to identify the commonalities of the deficits across the number of cognitive tests or, common errors in the various tests and identify their common "denominators" in the brain networks. The qualitative characterization of cognitive performance might be beneficial in addressing diffuse cognitive alterations presumably caused by the dysconnectivity of the distributed brain networks. Therefore, in the review, we use this approach in the description of standardized tests in the scope of potential errors in patients with schizophrenia with a subsequent reference to the brain networks.

Regional structural impairments outside lesions are associated with verbal short-term memory deficits in chronic subcortical stroke

Background and Purpose

We aimed to explore the neural mechanisms of verbal short-term memory (VSTM) impairment in subcortical stroke by evaluating the contributions of lesion and remote grey matter volume (GMV) reduction.

Results

There was no significant correlation between lesions and VSTM. In stroke patients with left lesions, GMV reductions in the right middle frontal gyrus and in the left inferior frontal gyrus were positively correlated with VSTM impairment. In patients with right lesions, GMV reduction in the right dorsal posterior cingulate cortex was positively correlated with VSTM impairment.

Materials and Methods

Ninety-seven patients with chronic subcortical ischemic stroke and seventy-nine healthy controls underwent VSTM and structural MRI examinations. Voxel-based lesion symptom mapping was used to identify correlations between lesions and VSTM. Voxel-wise comparisons were used to identify brain regions with significant GMV reduction in patients with left and right lesions. These regions were used in correlation analyses between GMV and VSTM in each patient subgroup.

Conclusions

These findings suggest that VSTM impairment in subcortical stroke is associated with secondary regional structural damage in non-lesion regions, rather than with the lesion itself. Moreover, different neural substrates may underlie VSTM impairment in stroke patients with left and right lesions.

Pre-therapy Neural State of Bilateral Motor and Premotor Cortices Predicts Therapy Gain After Subcortical Stroke: A Pilot Study

OBJECTIVE

The aim of the study was to examine whether neural state of spared motor and premotor cortices captured before a therapy predicts therapy-related motor gains in chronic subcortical stroke.

DESIGN

Ten survivors, presenting chronic moderate upper limb impairment, underwent proton magnetic resonance spectroscopy, magnetic resonance imaging, clinical, and kinematics assessments before a 4-wk impairment-oriented training. Clinical/kinematics assessments were repeated after therapy, and motor gain was defined as positive values of clinical upper limb/elbow motion changes and negative values of trunk motion changes. Candidate predictors were N-acetylaspartate-neuronal marker, glutamate-glutamine-indicator of glutamatergic neurotransmission, and myo-inositol-glial marker, measured bilaterally within the upper limb territory in motor and premotor (premotor cortex, supplementary motor area) cortices. Traditional predictors (age, stroke length, pre-therapy upper limb clinical impairment, infarct volume) were also investigated.

RESULTS

Poor motor gain was associated with lower glutamate-glutamine levels in ipsilesional primary motor cortex and premotor cortex (r = 0.77, P = 0.01 and r = 0.78, P = 0.008, respectively), lower N-acetylaspartate in ipsilesional premotor cortex (r = 0.69, P = 0.02), higher glutamate-glutamine in contralesional primary motor cortex (r = -0.68, P = 0.03), and lower glutamate-glutamine in contralesional supplementary motor area (r = 0.64, P = 0.04). These predictors outperformed myo-inositol metrics and traditional predictors (P ≈ 0.05-1.0).

CONCLUSIONS

Glutamatergic state of bilateral motor and premotor cortices and neuronal state of ipsilesional premotor cortex may be important for predicting motor outcome in the context of a restorative therapy.

Repetition-lag memory training is feasible in patients with chronic stroke, including those with memory problems

PRIMARY OBJECTIVE

Repetition-lag memory training was developed to increase individuals' use of recollection as opposed to familiarity in recognition memory. The goals of this study were to examine the feasibility of repetition-lag training in patients with chronic stroke and to explore whether the training might show suggestions of transfer to non-trained tasks.

RESEARCH DESIGN

Quasi-experimental.

METHODS AND PROCEDURES

Patients (n = 17) took part in six repetition-lag training sessions and their gains on the training and non-trained tasks were compared to those of age-matched healthy controls (n = 30).

MAIN OUTCOMES AND RESULTS

All but two patients completed the training, indicating that the method is feasible with a wide range of patients with stroke. The amount patients gained on the training task was similar to that of healthy controls (that is, the Group × Time interactions were by-and-large not significant), suggesting that patients with stroke might benefit to the same degree as healthy adults from this training. Both groups showed some indication of transfer to the non-trained backward digit span task and visuospatial memory.

CONCLUSIONS

These findings show that repetition-lag memory training is a possible approach with patients with stroke to enhance recollection. Further research on the method's efficacy and effectiveness is warranted.

Improvement of language functions in a chronic non-fluent post-stroke aphasic patient following bilateral sequential theta burst magnetic stimulation

In chronic non-fluent aphasia patients, inhibition of the intact right hemisphere (RH), by transcranial magnetic stimulation (TMS) or similar methods, can induce improvement in language functions. The supposed mechanism behind this improvement is a release of preserved left hemisphere (LH) language networks from RH transcallosal inhibition. Direct stimulation of the damaged LH can sometimes bring similar results too. Therefore, we developed a novel treatment approach that combined direct LH (Broca's area (BA)) stimulation, by intermittent theta burst stimulation (TBS), with homologue RH area's inhibition, by continuous TBS. We present the results of application of 15 daily sessions of the described treatment approach in a right-handed patient with chronic post-stroke non-fluent aphasia. The intervention appeared to improve several language functions, but most notably propositional speech, semantic fluency, short-term verbal memory, and verbal learning. Bilateral TBS modulation of activation of the language-related areas of both hemispheres seems to be a feasible and promising way to induce recovery in chronic aphasic patients. Due to potentially cumulative physiological effects of bilateral stimulation, the improvements may be even greater than following unilateral interventions.

Handgrip-Related Activation in the Primary Motor Cortex Relates to Underlying Neuronal Metabolism After Stroke

BACKGROUND

Abnormal task-related activation in primary motor cortices (M1) has been consistently found in functional imaging studies of subcortical stroke. Whether the abnormal activations are associated with neuronal alterations in the same or homologous area is not known.

OBJECTIVE

Our goal was to establish the relationships between M1 measures of motor-task-related activation and a neuronal marker, N-acetylaspartate (NAA), in patients with severe to mild hemiparesis.

METHODS

A total of 18 survivors of an ischemic subcortical stroke (confirmed on T2-weighted images) at more than six months post-onset and 16 age- and sex-matched right-handed healthy controls underwent functional MRI during a handgrip task (impaired hand in patients, dominant hand in controls) and proton magnetic resonance spectroscopy ((1)H-MRS) imaging. Spatial extent and magnitude of blood oxygen level-dependent response (or activation) and NAA levels were measured in each M1. Relationships between activation and NAA were determined.

RESULTS

Compared with controls, patients had a greater extent of contralesional (ipsilateral to impaired hand, P < .001) activation and a higher magnitude of activation and lower NAA in both ipsilesional (P = .008 and P < .001, respectively) and contralesional (P < .0001, P < .05) M1. There were significant negative correlations between extent of activation and NAA in each M1 (P = .02) and a trend between contralesional activation and ipsilesional NAA (P = .08) in patients but not in controls.

CONCLUSIONS

Our results suggest that after stroke greater neuronal recruitment could be a compensatory response to lower neuronal metabolism. Thus, dual-modality imaging may be a powerful tool for providing complementary probes of post-stroke brain reorganization.

Comparison of two models of hemispheric specialization with unilaterally lesioned patients: material-specific impairment vs response-bias distortion

Validity of two models of hemispheric specialization was compared. The "material-specific impairment" model was radicalized as postulating that left hemisphere (LH) lesions impair processing of verbal material and that right hemisphere (RH) lesions impair processing of visuospatial material, independently of response-bias distortions. The "response-bias distortion" model was radicalized as postulating that LH lesions distort response style toward omissiveness and that RH lesions distort response style toward commissiveness, regardless of material-specific impairments. Participants had comparable left (N=27) or right (N=24) hemisphere cortical lesions having occurred between birth and early adolescence. Four cognitive neuropsychological tests were adjusted to optimize applicability and comparability of the two theoretical models: Rey Complex Figure, Kimura's Recurring Figures, the Story Recall subtest of the Children's Memory Scale, and the California Verbal Learning Test. Both models significantly, independently, and equally distinguished the LH from the RH patients. Both these forms of hemispheric specialization seemed to be implemented very early in life and very rigidly. Intrahemispheric lesion sites, e.g., frontal vs nonfrontal, held no significant relation to the effects described above.

Cognitive deficits after subcortical infarction are comparable with deficits after cortical infarction

BACKGROUND AND PURPOSE

Cerebral cortical infarctions are often considered to be associated with more severe cognitive deficits than subcortical infarctions, but the evidence is conflicting. We compared early and late cognitive deficits between cortical and subcortical lesions.

METHODS

Consecutive patients with first-ever cortical (n = 61) or subcortical (n = 71) cerebral infarctions were assessed neuropsychologically after a mean of 8 days and again at 6 months after infarction. Examinations included evaluation of verbal memory, executive functions, psychomotor speed and visuospatial function as well as orientation, insight and mood state. At 6 months, verbal and non-verbal reasoning were also evaluated. Neurological examinations included National Institutes of Health Stroke Scale and Barthel Index at both time-points and the modified Rankin Scale at 6 months.

RESULTS

In the acute phase, memory (P = 0.007), especially delayed verbal recall (P = 0.005), was more severely affected in patients with subcortical infarctions than in those with cortical infarctions, and this trend persisted at 6 months post-infarction. Psychomotor speed (P = 0.040) was lower in the subcortical group in the acute phase than in the cortical group. Neurological scores did not differ between the two groups either in the acute phase or at 6 months.

CONCLUSIONS

Patients with subcortical cerebral infarctions may have even worse cognitive profiles than patients with cortical infarctions.