MRI Assessment Of Brain Structural And Functional Changes In Chronic Stroke Patients

Background and purpose The incidence of stroke increased year by year, accounting for 75%-80% of all cerebrovascular disease. The disease has a high morbidity, long duration, recovery slowly characteristics. Clinically, patients ofter experience motor, sensory, and cognition dysfunction, which affects the quality of life of patients seriously. Brain is a complex architecture consists of structural and functional variant units in cortical and subcortical areas, which interact with each other to well coordinate complex and delicate sensory-motor functions. Focal cerebral or subcortical ischemia within the motor pathway may cause serious movement related dysfunction. The motor and cognitive function of stoke patients may experience recovery automatically, which is grateful to neuronal plasticity. Cerebral structure and function is essential for neuronal recovery of stroke patients. It is a hotspot in neuroscience and has important clinical significance. We aimed to used voxel-based morphometry(VBM) analysis, resting-state cerebral blood flow(CBF) and functional connectivity(FC) to investigate cortical structural, perfusion and functional changes in well-recovered patients 6 months after subcortical ischemic stroke.Materials and methods A total of 29 well-recovered patients 6 months after subcortical ischemic stroke stroke(22 males and 7 females) and 30 age, gender and the years of education matched healthy subjects(18 males and 12 females) were investigated to undergo multimodal MRI techniques and behavioral tasks. The imaging data were acquired using GE Discovery MR 750 3.0 Tesla MR scanner. Subjects underwent 3D-BRAVO series, 3D pseudo-continuous arterial spin labeling(3D-p CASL) imaging and resting-state functional magnetic resonance(rsf MRI) scan. 1. The structural images were acquired by a brain volume(BRAVO) sequence and acquire 188 images. The perfusion imaging was performed using a 3D p CASL sequence and acquire 96 perfusion images and 48 cerebral images. rs-f MRI data were obtained using a gradient-echo single-shot echo-planar imaging sequence and acquire 6080 rsf MRI images. 2. The GMV were calculated using the optimized VBM technique implemented with SPM8 in Matlab. Include segmented, registration, spatial normalization, resampled, smoothed with an FWHM kernel of 8 mm. The CBF maps were processing via SPM8 in Matlab. We normalized the CBF images by dividing the mean CBF of the whole brain and spatially smoothed with a Gaussian kernel of 8 × 8 × 8 mm3 FWHM. 3. The rs-f MRI data were preprocessed using SPM8 and DPARSFA software including slice timing, realignment, spatial normalization, resampling, filter and smoothed. Then ROI-based rs FC analysis was performed to determine functional reorganization in CBF significant difference regions. 4. The GLM was applied to quantitatively compare group differences in GMV?CBF and rs FC throughout the whole brain with age, gender and the years of education as covariates of no interest with SPM8. Moreover, We performed partial correlation analysis to investigate the association between the clinical behavior scores and the statistics results of GMV, CBF and rs FC with SPSS 17.0.Results 1. Compared with healthy controls, the stroke patients exhibited increased GMV in contralesional supplementary motor area(SMA)(P< 0.05, cluster size >720 voxels). 2. The voxel-wise analysis showed that the well-recovered stroke patients exhibited increased CBF in contralesional superior frontal gyrus(SFG) and supramarginal gyrus(SMG) compared with normal controls(P< 0.05, cluster size >1054 voxels). After GMV correction, the increased CBF regions were the same as the regions without GMV correction. 3. Results showed patients exhibited increased FC in contralateral middle temporal gyrus(MTG) and contralateral SMG(P < 0.05, cluster size > 149 voxels). 4. Moreover, the increased CBFs of the contralesional SFG(r=-0.41, P= 0.04), and supramarginal gyrus(SMG)(r=-0.42, P= 0.04) were all significant negative correlation with TMT-B.Conclusions 1. We identified the gray matter structural plasticity and functional reorganization were coexisted in the contralesional hemisphere in the subcortical stroke patients with well-recovery global motor function. Moreover, Increased CBF were correlated with cognitive functional may represent a compensatory reorganization for the cognitive functional decline of subcortical stroke patients 2. Multi-modal MRI to explore brain structural and function of stroke patients may contribute to understand neuronal plasticity and functional reorganization in stroke recovery. It may have the potential of the imaging biomarkers for stroke recovery.