A Multimodal MRI Study Of Primary Motor Area After Stroke

Objective:To investigate the neural mechanisms of motor recovery after stroke, we explored the cortical structural changes caused by subcortical stroke and related functional reorganization in well-recovered patients by investigating changes in cortical thickness and the ralated resting-state functional magnetic resonance imaging (rs-fMRI) changes in motor related areas.Methods:Twenty-eight well-recovered patients (18males and10females) with a unilateral chronic infarction of basal ganglia area were compared with twenty-five age-and sex-matched healthy participants (11males and14females). GE3.0T HDX MR Scanner with a8-channel head coil was used to obtain high resolutions anatomy images and fMRI data in resting state. Cortical thickness was calculated using Freesurfer V.5.1.0software. The rs-fMRI data were processed with the software of Matlab, SPM8and REST. According to the results in cortical thickness, we defined the areas differed in cortical thickness between patients and healthy subjects as ROIs for the next ROI-based ReHo analyses and voxel-based functional connectivity analyses. The ROI-based group comparisons of cortical thickness and ReHo were performed using GLM with age and gender as the nuisance covariates. Group comparison of functional connectivity were performed using two-sample t-test in SPM8controlling for age and gender.Results:We found a significant decreased area in ipsilesional primary motor area of cortical thickness in chronic stroke patients compared to healthy subjects (using a single vertex threshold (P<0.05, uncorrected) with a cluster size threshold of P<0.05derived from a Monte Carlo simulation method). ROI-based ReHo analysis revealed that patients had higher ReHo values than healthy subjects in the area with decreased cortical thickness (P=0.026<0.05, uncorrected). Compared with healthy subjects, patients demonstrated higher functional connectivity with the bilateral sensomotor areas and supplementary motor area. On the contrary, functional connectivity with the contralesional cerebellum, bilateral insular lobes, frontal operculum, partial frontal and temporal lobes were decreased in patients with stroke (using a single voxel threshold (P<0.05, uncorrected) with AlphaSim corrected P<0.05at the cluster level).Conclusions:1. Chronic infarction of basal ganglia induced structural changes in ipsilesional primary motor area which may infered structral injury in cortical area remote from lesion site.2. Increased ReHo value in this injured area suggested increased functional synchronization and efficiency for information transferring and processing, as compensatory mechanism for structural damage.3. Increased functional connectivity in patients of the injured ROI with bilateral M1and SMA suggested that stroke may lead to functional changes in other related brain areas as another compensatory mechanism for stroke injury.4. The combination of structural and functional MRI should be an efficiency approach for exploring mechanisms of sroke recovery.