Investigation On The Reorganization Of Pyramidal Tract Fibers And Brain Cortex Function With Magnetic Resonance Imaging After Corona Radiata Infarct

Objective To investigate the proliferating reorganization of pyramidal tract fibers in both ipsilesional and contralesional hemisphere and its clinical features of cortex function reorganization after unilateral focus corona radiata infarct by use of diffusion tensor imaging(DTI)and resting-state functional MRI.Methods Twelve fully conscious patients with unilateral focal corona radiata infarct within 7 days infarction onset and with obvious motor function defect,such as body paralysis,without any history of CNS disease were enrolled as the observation group.Twelve healthy volunteers with age and gender matched the patients were chosen as the control group.All patients underwent MRI examination at three time points,within one week(W1),four weeks(W4),three months(W12)after infarct onset,while controls underwent the same MRI examination just one time.Every patients were evaluated with motor function part of National Institutes of Health Stroke Scale(NIHSS),simple Fugl-Meyer score(FM),Barthel Index(BI)to assess neurological function deficits,the CNS limb motor function defect,and the ability of daily living.A Siemens 3.0T whole-body MRI scan was used to acquire T1 anatomy images,diffusion weighted imaging(DTI),diffusion tensor imaging and rest-state functional MRI data.All data from MRI scan was processed after being transported to computer terminal.DTI data was processed with the following steps:(1)preprocessing of original data;(2)identifying regions of interest(ROI)in infarcts center,peri-infarct,ipsilesional centrum semiovale,ipsilesional internal capsule,ipsilesional cerebral peduncle and contralesional corona radiata respectively;(3)estimation DTI metrics of ROIs,such as radial diffusivity(RD),axial diffusivity(AD),fractional anisotropy(FA),mean diffusivity(MD).Then rs-f MRI data was processed with the following steps:(1)preprocessing of original data,such as slice timing,head-motion correction,spatial normalization,image smoothing,detrend,brain nuisance covariates regression;(2)generation of individual regional homogeneity(Re Ho)maps from each participant by calculating the KCC value of each voxel in the whole brain with the software REST.(3)calculation the difference of Re Ho by performing two sample t-test between the experimental and control groups at three time points,and by performing a repeated measures analysis of variance(RMANOVA).(4)calculation the voxel wise functional connectivity(FC)after extracting the area in which the Re Ho had a common significantly difference regions in the experimental than in the control groups at three time points as ROI;calculation the ROI wise FC after definiting bilateral primary motor cortex(M1)as ROI1 and ROI2 respectively.To investigate the relationship between the percent change of DTI parameter values and of nerve function score after 12 weeks infarct onset,spearman correlation analysis was used,with a formula of[(W12-W1)/W1]×100% to calculate the percent change.All data comparisons between the experimental and control groups at three time points were performed by two sample t-test.Inter-groups comparisons in observation groups were performed by RMANOVA,then least squares difference(LSD)method was used to analysis the the data between different time points.Results 1.During the observation period,the NIHSS score decreased gradually over time,meanwhile FM score and BI increased gradually over time.The FA,AD values of peri-infarct and ipsilesional internal capsule were gradually increased over time compared with matched regions in controls.Spearman correlation analysis showed that the increased percentage of FA and AD values in peri-infarct and ipsilesional internal capsule negatively correlated with the the deseased percentage of NIHSS,but positively correlated with the increased percentage of the percent change of BI and FM scores.2.Compared with the control group,the observation group presented increased Re Ho values in ipsilesional supplementary motor area(SMA)at W1,in bilateral SMA and contralesional primary motor area(M1)at W4,but no difference at W12.Bilateral cerebellar cortex of observation group exhibited increased Re Ho values at different time points according inter-groups RMANOVA.3.According the statistic difference from Re Ho maps,ipsilesional SMA was defined as ROI.The result of voxel wise FC exhibited increased FC in ipsilesional frontal lobe at W1,in contralesional precentral gyrus at W4,but exhibited no different FC at W12 with almost all stroke patients' motor function recovery to normal.4.The FC between ipsilesional M1 and contralesional M1 increased gradually over time and to peak at W4 accompanied by motor function recovery,then decreased to controls level with no statistical significance.5.The increased percentage of FC between bilateral M1 positively correlated with the increased percentage of the percent change of BI and FM scores,but had no correlation with the percent change of NIHSS scores.Conclusion 1.The pyramidal tract fibers in the peri-infarct and ipsilesional internal capsule exhibited a proliferative reorganization after unilateral focus corona radiata infarct onset,with motor function recovery,prompting that the proliferative reorganization of pyramidal tract fibers in the peri-infarct and ipsilesional internal capsule may promoted the recovery of neurological function.2.The increased Re Ho values in bilateral SMA,cerebellar cortex and contralesional M1 might compensate the motor function defects caused by corona radiata infarct,then promoted the recovery of motor function.3.The motor cortex in patients with unilateral focus corona radiata infarct began to exhibit FC earlier than other stroke patients where infarct located not in corona radiata.Meanwhile the increased FC between ipsilesional M1 and contralesional M1 might compensated the decreased FC between the bilateral primary sensorimotor cortex,then promoted the recovery of motor function.