Gray Matter Volume Changes And Verbal Short-Term Memory Deficits In Chronic Subcortical Stroke

Objective:Although changes of gray matter following subcortical stroke have been reported in some neuroimaging studies,seldom pays attention to the influence of lesion hemisphere and the degree of motor function recovery on gray matter volume(GMV)changes.This study aimed to investigate the effects of lesion side and degree of motor function recovery on GMV difference relative to healthy controls in right-handed subcortical stroke.In addition,Although verbal short-term memory(VSTM)impairment following stroke have been reported in some studies,the neural mechanisms underlying VSTM impairment after stroke remain largely unknown.We aimed to explore the neural mechanisms of VSTM impairment in subcortical stroke by evaluating the contributions of lesion and remote gray matter volume(GMV)reduction.Subjects and Methods:A total of 97 chronic subcortical stroke patients(72 males and 25 females)with different degree of motor function recovery,involving of the internal capsule and neighboring regions were included.79 age and sex-matched healthy subjects(50males and 29 females)were also recruited as controls.Structural images were acquired using a 3.0 T scanner.First,we divided the chronic subcortical stroke patients into two subgroups based on lesion side,namely the left-sided patients group and the right-sided patients group.Then,we divided the left-sided patients group and the right-sided patients group into CR(complete recovery)and PR(partial recovery)group respectively,according to the degree of motor function recovery.And the left-sided patients group and the right-sided patients group were analyzed respectively: the general linear model was used to compare group differences of GMV between CR,PR and healthycontrols in a voxel-wise manner with age,sex and scanners as nuisance variables;then brain regions with GMV changes were extracted to perform post-hoc analyses to explore whether CR and PR group exhibit similar GMV difference relative to healthy controls;finally,a partial correlation analysis was used to investigate correlations between GMV of these areas and Fugl-Meyer Assessment(FMA)with age,sex and scans as the nuisance variables in PR patients.In addition,voxel-based lesion symptom mapping was used to identify correlations between lesions and VSTM.Voxel-wise comparisons were used to identify brain regions with significant GMV reduction in patients with left and right lesions with age,sex and scanners as nuisance variables.These regions were used in correlation analyses between GMV and VSTM in each patient subgroup.Results:1.Compared with healthy controls,left-lesion patients exhibited GMV increase in the right paracentral lobule(PCL)and middle occipital gyrus(MOG);right-lesion patients demonstrated GMV increase in the bilateral PCL and supplementary motor area(SMA)and the right MOG.2.Compared with healthy controls,only right-lesion patients demonstrated GMV decrease in the right precentral gyrus(Pre CG).3.Patients with complete and partial motor recovery showed similar degree of GMV increase.4.There was no significant correlation between lesions and VSTM.5.Patients with left lesions showed decreased GMV in the left sensorimotor cortex(SMC),left insular cortex,left middle temporal cortex,left middle occipital cortex,left triangular part of the inferior frontal gyrus(IFG),and right middle frontal gyrus(MFG)compared with healthy controls;patients with right lesions showed decreased GMV in the right SMC,right insular cortex,right middle temporal cortex,right dorsal posterior cingulate cortex(PCC),right orbitofrontal cortex,and left superior frontal cortex compared with healthy controls.6.In stroke patients with left lesions,GMV reductions in the right middle frontal gyrus and in the left inferior frontal gyrus were positively correlated with VSTMimpairment;in patients with right lesions,GMV reduction in the right dorsal posterior cingulate cortex was positively correlated with VSTM impairment.Summary:1.Compared with healthy controls,right-lesion patients exhibited more extensive GMV changes than left-lesion patients,suggesting a lesion-side effect on GMV changes in right-handed chronic subcortical stroke.2.Compared with healthy controls,chronic subcortical stroke patients exhibited more extensive GMV increase than GMV decrease,suggesting that there exists structural reorganization at the chronic stage of stroke.3.The CR and PR patients showed similar GMV increase relative to healthy controls,suggesting the lack of dependency of the degree of motor recovery on structural reorganization in subcortical stroke.4.VSTM impairment in subcortical stroke is associated with secondary regional structural damage in non-lesion regions,rather than with the lesion itself,suggesting secondary regional atrophy contributes to VSTM impairment in subcortical stroke patients.5.Different neural substrates may underlie VSTM impairment in stroke patients with left and right lesions,thus the lesion-side effect should be considered in future studies on cognitive function following stroke.Conclusions There exists extensive structural reorganization at the chronic stage of subcortical stroke,which is affected by lesion-side,and the degree of motor recovery does not depend on structural reorganization.Furthermore,VSTM impairment in subcortical stroke is associated with secondary regional structural damage in non-lesion regions,rather than with the lesion itself,and different neural substrates may underlie VSTM impairment in stroke patients with left and right lesions.