A Multimodal FMRI Study Of Changes Between Structure And Function After Chronic Pontine Stroke

Objective:To investigate the neural mechanisms of motor recovery after chronic pontine stroke, we explored the structural changes caused by pontine stroke and related functional reorganization in well-recovered patients by investigating changes of gray matter volumes、resting-state ReHo and ALFF, brain activity strength and task-state functional connectivity in motor related areas.Methods:Sixteen well-recovered patients (13males and3females) with a unilateral chronic infarction of pontine 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 datas in resting and task state. A functional fMRI block with bilateral hands motion was designed. The datas were processed with the softwares of Matlab, SPM8and REST. Using GLM with gender and age as the nuisance covariates to analyze the two sample t-test, compare the difference of gray matter volumes、ReHO、ALFF and brain activity between stroke patients and normal subjects. Extraction of the activity differences regions as ROI, for the voxel-vise functional connectivity analysis, compared the difference of functional connectivity between the two groups.Results:Compared to healthy subjects, we found that a significant decreased area in left cerebellum (ROI1) and the increased areas in contralesional M1and bilateral SMA of gray matter volumes in chronic pontine stroke patients. A decreased area in left cerebellum (ROI2) of ReHo values in chronic pontine stroke patients. A decreased area in left cerebellum (ROI3) and the increased areas in ipsilesional IPL and prefrontal cortex of ALFF values in chronic pontine stroke patients. Three ROIs were overlapped. The overplapping percent of ROI1and ROB was5.3%, the overlapping percent of ROI2and ROI3was34.3%, the overlapping percent of ROI1and ROI2was0%. The activation level of affected hemisphere SMC was higher in pontine stroke patients when the affected hand moved (using a cluster size threshold of P<0.005derived from a Monte Carlo simulation method). Extraction of the affected hemisphere SMC as ROI, for the voxel-vise functional connectivity analysis, we found higher functional connectivity with contralesional PMC, bilateral anterior lobe of cerebellum and middle temporal gyrus in the patients. On the contrary, functional connectivity with the contralesional posterior lobe of cerebellum, contralesional angular grus, ipsilesional supramarginal gyrus and bilateral prefrontal lobes.(using a single voxel threshold (P<0.05, uncorrected) with AlphaSim corrected P<0.05at the cluster level).Conclusions:1. Chronic infarction of pone induced structural changes in bilateral cerebellum, contralesional Ml and bilateral SMA, which suggested structural plasticity may compensate for motor function.2. Decreased ReHo and ALFF values in the left cerebullm suggested neuron functional synchronization and amplitude decreased. Increased ALFF value in the ipsilesional IPL and prefrontal areas suggested increased functional synchronization and efficiency for information transferring and processing, as compensatory mechanism for structural damage.3. ROI1and ROI3had less overlapped, ROI2and ROI3had partly overlapped, ROI1and ROI2had no overlapped, which maybe associated with crossed cerebellar diaschisis.4. SMC increased activity in the affected hemisphere, which reflected the cortex compensatory function.5. Functional connectivity increased between contralesional SMC and motor related brain regions, which reflected that motor recovery was improved as regional compensatory mechanism.