Cerebral blood flow and cognitive outcome after pediatric stroke in the middle cerebral artery.

Adaptive recovery of cerebral perfusion after pediatric arterial ischemic stroke (AIS) is sought to be crucial for sustainable rehabilitation of cognitive functions. We therefore examined cerebral blood flow (CBF) in the chronic stage after stroke and its association with cognitive outcome in patients after pediatric AIS. This cross-sectional study investigated CBF and cognitive functions in 14 patients (age 13.5 ± 4.4 years) after pediatric AIS in the middle cerebral artery (time since AIS was at least 2 years prior to assessment) when compared with 36 healthy controls (aged 13.8 ± 4.3 years). Cognitive functions were assessed with neuropsychological tests, CBF was measured with arterial spin labeled imaging in the anterior, middle, and posterior cerebral artery (ACA, MCA, PCA). Patients had significantly lower IQ scores and poorer cognitive functions compared to healthy controls (p < 0.026) but mean performance was within the normal range in all cognitive domains. Arterial spin labeled imaging revealed significantly lower CBF in the ipsilesional MCA and PCA in patients compared to healthy controls. Further, we found significantly higher interhemispheric perfusion imbalance in the MCA in patients compared to controls. Higher interhemispheric perfusion imbalance in the MCA was significantly associated with lower working memory performance. Our findings revealed that even years after a pediatric stroke in the MCA, reduced ipsilesional cerebral blood flow occurs in the MCA and PCA and that interhemispheric imbalance is associated with cognitive performance. Thus, our data suggest that cerebral hypoperfusion might underlie some of the variability observed in long-term outcome after pediatric stroke

Arterial spin labelling shows functional depression of non-lesion tissue in chronic Wernicke’s aphasia

Behavioural impairment post-stroke is a consequence of structural damage and altered functional network dynamics. Hypoperfusion of intact neural tissue is frequently observed in acute stroke, indicating reduced functional capacity of regions outside the lesion. However, cerebral blood flow is rarely investigated in chronic stroke. This study investigated cerebral blood flow in individuals with chronic Wernicke’s aphasia and examined the relationship between lesion, cerebral blood flow and neuropsychological impairment. Arterial spin labelling cerebral blood flow imaging and structural MRIs were collected in 12 individuals with chronic Wernicke’s aphasia and 13 age-matched control participants. Joint independent component analysis (jICA) investigated the relationship between structural lesion and hypoperfusion. Partial correlations explored the relationship between lesion, hypoperfusion and language measures. Joint ICA revealed significant differences between the control and WA groups reflecting a large area of structural lesion in the left posterior hemisphere and an associated area of hypoperfusion extending into grey matter surrounding the lesion. Small regions of remote cortical hypoperfusion were observed, ipsilateral and contralateral to the lesion. Significant correlations were observed between the neuropsychological measures (naming, repetition, reading and semantic association) and the jICA component of interest in the WA group. Additional ROI analyses found a relationship between perfusion surrounding the core lesion and the same neuropsychological measures

Cerebral blood flow imbalance is associated with motor outcome after pediatric arterial ischemic stroke.

Cerebral hemodynamics after arterial ischemic stroke (AIS) in children are largely unknown. This study aims to explore long-term cerebral perfusion balance of vital tissue and its relation to motor outcome after childhood AIS. Patients diagnosed with childhood AIS (≤16 years at diagnosis, time since stroke ≥2 years) and typically developing peers were examined. Hemiparesis was classified according to the Pediatric Stroke Outcome Measure. Manual ability was assessed using the ABILHAND-Kids questionnaire. Cerebral blood flow was measured by arterial spin labeling and analyzed in the following brain regions: the hemispheres, the territory of the anterior cerebral artery (ACA), the middle cerebral artery (MCA), and in subregions of the MCA territory (MCA anterior, middle, posterior). To assess cerebral perfusion balance, laterality indices were calculated using cerebral blood flow in the ipsi- and contralesional hemisphere. Laterality indices were compared between stroke patients with and without hemiparesis, and peers. Twenty participants diagnosed with AIS were included (12 boys, 8 girls; mean age 14.46±4.96 years; time since stroke 8.08±3.62 years); 9 (45%) were diagnosed with hemiparesis. Additionally, 47 typically developing peers (21 boys, 26 girls; mean age 14.24±5.42 years) were studied. Laterality indices were higher in stroke patients and oriented to the contralesional hemisphere in all brain regions except the ACA territory and MCA posterior subregion. This was significantly different from peers, who showed balanced laterality indices. There was a significant correlation between laterality indices and manual ability, except in the ACA territory. AIS is associated with long-term alterations of cerebral blood flow in vital tissue, even in patients without hemiparesis. The degree of imbalance of cerebral perfusion in children after AIS is associated with manual ability

Neuroplasticity of language networks in aphasia: advances, updates, and future challenges

Researchers have sought to understand how language is processed in the brain, how brain damage affects language abilities, and what can be expected during the recovery period since the early 19th century. In this review, we first discuss mechanisms of damage and plasticity in the post-stroke brain, both in the acute and the chronic phase of recovery. We then review factors that are associated with recovery. First, we review organism intrinsic variables such as age, lesion volume and location and structural integrity that influence language recovery. Next, we review organism extrinsic factors such as treatment that influence language recovery. Here, we discuss recent advances in our understanding of language recovery and highlight recent work that emphasizes a network perspective of language recovery. Finally, we propose our interpretation of the principles of neuroplasticity, originally proposed by Kleim and Jones (1) in the context of extant literature in aphasia recovery and rehabilitation. Ultimately, we encourage researchers to propose sophisticated intervention studies that bring us closer to the goal of providing precision treatment for patients with aphasia and a better understanding of the neural mechanisms that underlie successful neuroplasticity.P50 DC012283 - NIDCD NIH HHSPublished versio

Brain plasticity following MI-BCI training combined with tDCS in a randomized trial in chronic subcortical stroke subjects: a preliminary study

Brain-computer interface-assisted motor imagery (MI-BCI) or transcranial direct current stimulation (tDCS) has been used in stroke rehabilitation, though their combinatory effect is unknown. We investigated brain plasticity following a combined MI-BCI and tDCS intervention in chronic subcortical stroke patients with unilateral upper limb disability. Nineteen patients were randomized into tDCS and sham-tDCS groups. Diffusion and perfusion MRI, and transcranial magnetic stimulation were used to study structural connectivity, cerebral blood flow (CBF), and corticospinal excitability, respectively, before and 4 weeks after the 2-week intervention. After quality control, thirteen subjects were included in the CBF analysis. Eleven healthy controls underwent 2 sessions of MRI for reproducibility study. Whereas motor performance showed comparable improvement, long-lasting neuroplasticity can only be detected in the tDCS group, where white matter integrity in the ipsilesional corticospinal tract and bilateral corpus callosum was increased but sensorimotor CBF was decreased, particularly in the ipsilesional side. CBF change in the bilateral parietal cortices also correlated with motor function improvement, consistent with the increased white matter integrity in the corpus callosum connecting these regions, suggesting an involvement of interhemispheric interaction. The preliminary results indicate that tDCS may facilitate neuroplasticity and suggest the potential for refining rehabilitation strategies for stroke patients

Neuroplasticity of Language Networks in Aphasia: Advances, Updates, and Future Challenges

Researchers have sought to understand how language is processed in the brain, how brain damage affects language abilities, and what can be expected during the recovery period since the early 19th century. In this review, we first discuss mechanisms of damage and plasticity in the post-stroke brain, both in the acute and the chronic phase of recovery. We then review factors that are associated with recovery. First, we review organism intrinsic variables such as age, lesion volume and location and structural integrity that influence language recovery. Next, we review organism extrinsic factors such as treatment that influence language recovery. Here, we discuss recent advances in our understanding of language recovery and highlight recent work that emphasizes a network perspective of language recovery. Finally, we propose our interpretation of the principles of neuroplasticity, originally proposed by Kleim and Jones (1) in the context of extant literature in aphasia recovery and rehabilitation. Ultimately, we encourage researchers to propose sophisticated intervention studies that bring us closer to the goal of providing precision treatment for patients with aphasia and a better understanding of the neural mechanisms that underlie successful neuroplasticity

Uloga nekontrastne magnetno-rezonantne perfuzije u dijagnostici, terapiji i prognozi kliničkog ishoda akutnog ishemijskog moždanog udara

Acute ischemic stroke (AIS) is an emergency condition causing the interruption of blood flow through one or more cerebral blood vessels. The discovery and application of advanced magnetic-resonance (MRI) techniques in clinical practice has significantly improved diagnostic accuracy in early detection of AIS, whereas the introduction of noncontrast arterial spin labeling (ASL) perfusion sequence is a significant milestone in neuroradiology. This research aimed to demonstrate MRI as the method of choice in early diagnostics of AIS that provides insight into diagnostic and prognostic parameters. We examined the influence of a specific ASL sequence findings on the AIS functional outcome, in correlation with other protocol sequences findings. The research was conducted as a prospective cross-sectional study at the Department of Radiology, Clinical Center Nis and the Department of Neuroradiology, University Hospital Pitié‐Salpêtrière, Paris. The study included 205 patients of both sexes (aged ≥18 years) fulfilling clinical criteria for the diagnosis of AIS of the anterior cerebral circulation. All patients were examined on GE MRI scanners (field strength of 3T), using an ischemia protocol. Results showed high efficiency of MRI in the detection of early hyperacute and acute ischemic lesions. The ASL perfusion sequence allows the detection of favorable AIS outcome predictors, primarily higher absolute cerebral blood flow (aCBF) values, the presence of arterial transient artifacts, and luxury perfusion. Significant certainty Aleksandra Z. Aracki-Trenkić DOKTORSKA DISERTACIJA 7 in the detection of the occlusion site is achieved through the correlation of ASL and susceptibility weighted angiography (SWAN) sequence findings with the possibility of assessing the etiological type of AIS. A multivariate logistic regression analysis found the most significant predictors of favorable functional outcome were the involvement of the territory on the diffusion sequence and aCBF values. In addition to early diagnosis of AIS, MRI with modern advanced sequences enables functional outcome prediction, thus influencing the choice of adequate therapy