Differences of cortical activation pattern between cortical and corona radiata infarct

Lesion-specific cortical activation following sensory stimulation in patients with subacute stroke

BACKGROUND

Sensory stimulation can play a fundamental role in the activation of the primary sensorimotor cortex (S1-M1), which can promote motor learning and M1 plasticity in stroke patients. However, studies have focused mainly on investigating the influence of brain lesion profiles on the activation patterns of S1-M1 during motor tasks instead of sensory tasks. Therefore, the objective of this study is to explore the lesion-specific activation patterns due to different brain lesion profiles and types during focal vibration (FV).

METHODS

In total 52 subacute stroke patients were recruited in this clinical experiment, including patients with basal ganglia hemorrhage/ischemia, brainstem ischemia, other subcortical ischemia, cortical ischemia, and mixed cortical-subcortical ischemia. Electroencephalograms (EEG) were recorded following a resting state lasting for 4 min and three sessions of FV. FV was applied over the muscle belly of the affected limb's biceps for 3 min each session. Beta motor-related EEG power desynchronization overlying S1-M1 was used to indicate the activation of S1-M1, while the laterality coefficient (LC) of the activation of S1-M1 was used to assess the interhemispheric asymmetry of brain activation.

RESULTS

(1) Regarding brain lesion profiles, FV could lead to the significant activation of bilateral S1-M1 in patients with basal ganglia ischemia and other subcortical ischemia. The activation of ipsilesional S1-M1 in patients with brainstem ischemia was higher than that in patients with cortical ischemia. No activation of S1-M1 was observed in patients with lesions involving cortical regions. (2) Regarding brain lesion types, FV could induce the activation of bilateral S1-M1 in patients with basal ganglia hemorrhage, which was significantly higher than that in patients with basal ganglia ischemia. Additionally, LC showed no significant correlation with the modified Barthel index (MBI) in all patients, but a positive correlation with MBI in patients with basal ganglia lesions.

CONCLUSIONS

These results reveal that sensory stimulation can induce lesion-specific activation patterns of S1-M1. This indicates FV could be applied in a personalized manner based on the lesion-specific activation of S1-M1 in stroke patients with different lesion profiles and types. Our study may contribute to a better understanding of the underlying mechanisms of cortical reorganization.

Exploring Representation of Diverse Samples in fMRI Studies Conducted in Patients With Cardiac-Related Chronic Illness: A Focused Systematic Review

Introduction/Purpose: Cardiovascular disease (CVD) is the leading cause of death worldwide, and in the United States alone, CVD causes nearly 840,000 deaths annually. Using functional magnetic resonance imaging (fMRI), a tool to assess brain activity, researchers have identified some brain-behavior connections and predicted several self-management behaviors. The purpose of this study was to examine the sample characteristics of individuals with CVD who participated in fMRI studies. Methods: A literature search was conducted in PubMed, CINAHL, and Scopus. No date or language restrictions were applied and research methodology filters were used. In October 2017, 1659 titles and abstracts were identified. Inclusion criteria were: (1) utilized an empirical study design, (2) used fMRI to assess brain activity, and (3) focused on patients with CVD-related chronic illness. Articles were excluded if they: were theory or opinion articles, focused on mental or neuropathic illness, included non-human samples, or were not written in English. After duplicates were removed (230), 1,429 titles and abstracts were reviewed based on inclusion criteria; 1,243 abstracts were then excluded. A total of 186 studies were reviewed in their entirety; after additional review, 142 were further excluded for not meeting the inclusion criteria. Forty-four articles met criteria and were included in the final review. An evidence table was created to capture the demographics of each study sample. Results: Ninety eight percent of the studies did not report the racial or ethnic composition of their sample. Most studies (66%) contained more men than women. Mean age ranged from 38 to 78 years; 77% reported mean age ≥50 years. The most frequently studied CVD was stroke (86%), while hypertension was studied the least (2%). Conclusion: Understanding brain-behavior relationships can help researchers and practitioners tailor interventions to meet specific patient needs. These findings suggest that additional studies are needed that focus on populations historically underrepresented in fMRI research. Researchers should thoughtfully consider diversity and purposefully sample groups by including individuals that are: women, from diverse backgrounds, younger, and diagnosed with a variety of CVD-related illnesses. Identifying and addressing these gaps by studying more representative samples will help healthcare providers reduce disparities and tailor interventions for all CVD populations.

Activation of less affected corticospinal tract and poor motor outcome in hemiplegic pediatric patients: a diffusion tensor tractography imaging study

The less affected hemisphere is important in motor recovery in mature brains. However, in terms of motor outcome in immature brains, no study has been reported on the less affected corticospinal tract in hemiplegic pediatric patients. Therefore, we examined the relationship between the condition of the less affected corticospinal tract and motor function in hemiplegic pediatric patients. Forty patients with hemiplegia due to perinatal or prenatal injury (13.7 ± 3.0 months) and 40 age-matched typically developing controls were recruited. These patients were divided into two age-matched groups, the high functioning group (20 patients) and the low functioning group (20 patients) using functional level of hemiplegia scale. Diffusion tensor tractography images showed that compared with the control group, the patient group of the less affected corticospinal tract showed significantly increased fiber number and significantly decreased fractional anisotropy value. Significantly increased fiber number and significantly decreased fractional anisotropy value in the low functioning group were observed than in the high functioning group. These findings suggest that activation of the less affected hemisphere presenting as increased fiber number and decreased fractional anisotropy value is related to poor motor function in pediatric hemiplegic patients.

The anatomical location of the corticobulbar tract at the corona radiata in the human brain: diffusion tensor tractography study

Many studies have reported on the anatomical location of the corticobulbar tract (CBT). However, no study has reported on the anatomical location of the corona radiata (CR). Using diffusion tensor tractography, we investigated the anatomical location of the CBT at the CR in normal subjects. Forty healthy normal subjects were enrolled in this study. Diffusion tensor images were acquired at 1.5-T, and the CBT was reconstructed using FMRIB software. The highest probabilistic location of the CBT was defined as the location on an axial slice in the upper and lower CRs. The CBT was located at an average of 49.13% and 49.91% in the antero-posterior direction between the most anterior point and the most posterior point of the lateral ventricle at the upper and lower CR, respectively. Regarding medio-lateral direction, between the midline and the most lateral point of the brain, the CBT was located at an average of 36.58% and 32.73% at the upper and lower CR, respectively. According to our findings, the CBT was located almost halfway between the most anterior point and the most posterior point of the lateral ventricle at the CR, and almost one third between the midline and the most lateral point of the brain at the CR.

Change of the anterior corticospinal tract on the normal side of the brain in chronic stroke patients: Diffusion tensor imaging study

We investigated change of the anterior corticospinal tract (CST) on the normal side of the brain in stroke patients, using diffusion tensor tractography (DTT). We recruited 32 stroke patients and 24 control subjects. Motricity Index and DTT for the whole and anterior CSTs were evaluated. According to findings, the fiber number of the anterior CST on the normal side of the brain of stroke patients was related to poor motor function of the affected extremities.

Brain connectivity plasticity in the motor network after ischemic stroke

The motor function is controlled by the motor system that comprises a series of cortical and subcortical areas interacting via anatomical connections. The motor function will be disturbed when the stroke lesion impairs either any of these areas or their connections. More and more evidence indicates that the reorganization of the motor network including both areas and their anatomical and functional connectivity might contribute to the motor recovery after stroke. Here, we review recent studies employing models of anatomical, functional, and effective connectivity on neuroimaging data to investigate how ischemic stroke influences the connectivity of motor areas and how changes in connectivity relate to impaired function and functional recovery. We suggest that connectivity changes constitute an important pathophysiological aspect of motor impairment after stroke and important mechanisms of motor recovery. We also demonstrate that therapeutic interventions may facilitate motor recovery after stroke by modulating the connectivity among the motor areas. In conclusion, connectivity analyses improved our understanding of the mechanisms of motor recovery after stroke and may help to design hypothesis-driven treatment strategies and sensitive measures for outcome prediction in stroke patients.

Review: Functional Neuroimaging Studies of Early Upper Limb Recovery After Stroke: A Systematic Review of the Literature

Background. Understanding mechanisms of recovery may result in new treatment strategies to improve motor outcome after stroke. Imaging techniques such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) allow changes in brain activity after stroke recovery to be identified. Objective. To systematically review serial imaging studies on recovery within 6 months poststroke, assess their methodological quality, and identify trends in the association between task-related brain activation patterns and functional upper limb recovery. Methods. A literature search was performed using Medline, PICARTA, and EMBASE databases. Studies were appraised using binary weighted methodological criteria for internal, statistical, and external validity. Results. Twenty-two of the 869 identified studies met the inclusion criteria. Studies showed methodological weaknesses with respect to controlling for task performance, selecting appropriate outcome measures, and adequate presentation and execution of statistical analysis. After stroke, motor task performance shows unilateral overactivation of motor and nonmotor areas, a posterior shift in activity in the primary motor cortex, and bilateral recruitment of associated motor and nonmotor areas. Concomitant with neurological recovery, overactivation appears to diminish longitudinally, but not in all patients. Conclusion . Despite methodological shortcomings and heterogeneity, trends can be discerned. However, statistically sound associations with recovery are not consistent. The challenges in future research will be, controlling for confounding factors, finding outcomes that specifically measure dexterity of the paretic limb, to control for the extent of white matter damage and changes in perfusion in order to establish the longitudinal construct validity of fMRI and PET with regard to upper limb recovery after stroke.

Basal Ganglionic Infarction Before Mechanical Thrombectomy Predicts Poor Outcome

Background and Purpose— Use of mechanical thrombectomy for acute cerebrovascular occlusions is increasing. Preintervention MRI patterns may be helpful in predicting prognosis.

Methods— We reviewed all Merci thrombectomy cases of either terminal ICA or M1 occlusions and classified them according to diffusion MRI patterns of (1) completed basal ganglia infarct (pure M1a), (2) near-completed basal ganglia infarct (incomplete M1a), and (3) relative sparing of deep MCA field (M1b). We compared the M1a and M1b patients with respect to neurological deficit on presentation, recanalization rates, hospital length of stay, and disability on discharge. We also determined whether deep MCA compromise predicted hematomal hemorrhagic transformation (HT) and whether this correlated with worse clinical outcome at discharge.

Results— The M1a group had worse pre-Merci NIHSS (21 versus 14, P =0.004), worse discharge NIHSS (12 versus 4, P <0.001), longer hospital length of stay (11.5 versus 6.4 days, P =0.003), and higher rates of discharge mRS ≥3 (OR 8.4, 95% CI 2.1 to 44.7) despite equivalent recanalization rates when compared to the M1b group. The M1a group had a higher rate of parenchymal hematomal HT (OR 6.7, 95% CI 1.02 to 183.3). Patients with such hematomal HT had higher rates of death or dependency discharge (100% versus 60%, OR=infinite).

Conclusions— Among patients with ICA and M1 occlusions, preintervention diffusion MRI evidence of advanced injury in the basal ganglia bodes worse dysfunction and disability at discharge, longer hospital stays, and higher rates of hemorrhage after intervention when compared to other diffusion patterns.

Improvement after constraint-induced movement therapy is independent of infarct location in chronic stroke patients

BACKGROUND AND PURPOSE

Disruption of the corticospinal tract at various locations in the brain has been shown to predict worse spontaneous motor recovery after stroke. However, the anatomic specificity of previous findings was limited by the categorical classification of infarct locations. Here we used computational methods to more precisely determine the specific anatomic locations associated with impaired motor ability. More important, however, our study also used these techniques to evaluate whether infarct location could influence motor outcomes after Constraint-Induced Movement therapy (CI therapy), a specific and controlled form of physical therapy.

METHODS

Quantitative voxel-based analyses were used to determine whether infarct location could predict either initial motor ability or clinical improvement after CI therapy in chronic stroke patients.

RESULTS

Although corona radiata infarcts were associated with worse in-laboratory motor ability at pretreatment, infarct location did not predict improvement in either the laboratory or the life situation after CI therapy.

CONCLUSIONS

The extent of improvement from CI therapy does not depend on the location of neurological damage, despite there being a pretreatment relationship between infarct location and in-laboratory motor ability. This dissociation could be explained by brain plasticity induced by CI therapy.