Lesion-location-dependent Structural Alterations In Subcortical Motor Pathway Stroke

Objective:Stroke is the second cause of death after coronary heart disease all over the world.Ischemic stroke displays considerable variance in lesion location,which has been associated with functional outcome.Although both capsular(CS)and pontine(PS)stroke commonly affect the subcortical motor pathway,they impair different nearby structures.A large number of studies have confirmed that structural damage and reorganization can occur in brain regions outside of the lesion in chronic stroke patients.Therefore,in this study,we compared the gray matter volume(GMV)differences among CS,PS and NC,aimed to investigate whether patients with different subcortical stroke lesions involving the motor pathway have different types of structural damage and reorganization.Subjects and methods:In this prospective study,with Institutional Review Board approval and after obtaining written informed consent of Tianjin Medical University General Hospital,structural MRI data were acquired in 115 CS patients,47 PS patients and 116 normal controls using four scanners from three hospitals.Neurologic functions of all the subjects were tested and the infarction sizes of stroke patients were measured.After preprocessing,MRI data of all the enrolled subjects were statistically analyzed.According to the lesion location,all the stroke patients were devided into left lesion group(LLG)and right lesion group(RLG)and analyzed seperately.The GMV of each voxel was compared between groups using voxel-based morphometry(VBM).Clusters with significant GMV differences were defined as regions of interest(ROIs),and the GMV of each ROI was compared between groups quantitatively.There were 3 parts in this study:1.Compare the GMV differences between CS and NC using independent-sample T test.2.Compare the GMV differences between PS and NC using independent-sample T test.3.Compare the GMV differences among CS,PS and NC using one-way analysis of covariance(ANCOVA).In order to verify the reliability of the VBM results,a surface-wise morphometry — Freesurfer was also used to compare the GMV difference between groups.Clusters in surface-based analysis with similar GMV changes as the original VBM analysis were defined as ROIs and perform surface-based post-hoc analyses.Group differences of GMV,cortical thickness(CT)and surface area(SA)of each ROI were compared quantitatively.Results:1.The GMV of the ipsilesional(IL)sensorimotor cortex(SMC)decreased in both left-and right-lesion CS patients.The GMV decreased in the bilateral(BL)cerebellum(CE),but increased in the contralesional middle frontal gyrus(MFG)and the bilateral supplementary motor area(SMA)in right-lesion CS patients.2.In both LLG and RLG,PS patients demonstrated decreased GMV in CE_BL.The left-lesion PS patients demonstrated increased GMV in SMA_BL.The right-lesion PS petients exhibited decreased GMV in bilateral anterior insular cortex(AIC)but increased GMV in bilateral paracentral lobule(PCL)and MFG_IL.3.In LLG and RLG,both CS and PS patients demonstrated decreased GMV in the AIC_IL and increased GMV in SMA_BL.CS patients showed reduced GMV in the SMC_IL,while PS patients showed reduced GMV in the CE_BL.In addition,the left-lesion PS showed increased GMV in the precuneus,whereas the right-lesion CS patients showed increased GMV in the MFG_IL.4.In the Freesurfer analysis,there were 3 clusters(including the SMC_IL in LLG and SMC_IL and AIC_IL in RLG)in surface-based analysis with similar GMV changes as the original VBM analysis.For the SMC_IL in LLG,both GMV and CT decreased in CS and PS.For the SMC_IL in the RLG,GMV,CT and SA all decreased in CS.For the AIC_IL in the RLG,GMV,CT and SA all decreased in the CS group,and the GMV and SA decreased in the PS group.Conclusion1.Capsular stroke exhibited structural damage in the sensorimotor area,whereas pontine stroke showed cerebellar atrophy,suggesting different patterns of secondary structural damage in the two patient subgroups.2.The SMA showed GMV increase in both capsular and pontine stroke,suggesting a potential target for rehabilitation in all subcortical stroke patients.3.Though both involved motor pathway,both capsular and pontine stroke patients showed secondary structural damage and reorganization in cognitive related brain areas,which may provide measures to assess and monitor cognitive function.4.These findings suggest different patterns of structural damage and reorganization in capsular versus pontine stroke patients,which may provide useful information in designing individualized rehabilitative strategies for these patients.