A Dynamic MRI Study Of Structure Changes About Primary Motor Cortex And Pyramidal Tract After Stroke

Objective:To investigate the underlying mechanisms of secondary changes in the volumes of motor-related cortical regions remote from infarct site, we explored the dynamic changes and time courses of cerebral structures including grey matter and white fiber in patients after subcortical stroke involving motor pathway. Voxel-based morphometry (VBM) and Diffusion Tensor Imaging (DTI) were combined together for data analysis.Methods:High-resolution structural MRI, DTI and neurological examinations were conducted at five consecutive time points (1week,2week,lmonth,3month,6month) during the year following stroke in13patients with a unilateral subcortical infarction involving motor pathways using the GE3.0T HDX MR Scanner with a8-channel head coil. Ten age-and sex-matched healthy participants (4males and6females) were also recruited as control group for comparison and underwent the same scans only one time. The data were processed with the softwares of Matlab, SPM8, and FSL4.1based on Linux platform. Freesurfer V.5.1.0was used to reconstruct the normal bilateral M1area. One-way ANOVA within subjects in SPM8was used to analyze the dynamic courses of bilateral Ml area grey matter volumes(GMV). Using one-way analysis of variance to compare the differences (FA、MD、λ|、λ⊥)of healthy (left) side pyramidal tract (PT) between patient and control group. Using GLM with gender and age as the nuisance covariates to analyze the changes of DTI indices (rFA、rMD、rλ|、rλ⊥) during time courses. Pearson correlation analysis was used to analyze the relationship of changes between the GMV and PT.Results:1. Eliminating the patients not completing the whole scans and having poor image quality resulting head moving,6stroke patients were finally enrolled.6age-and sex-matched healthy participants (3males and3females) were also recruited as control group for comparison.2. GMV changes:Significantly decreases of GMV were found in ipsilesional primary motor cortex. The dynamic changes:the GMV decreased in the first3months, then stabilized after3months (P<0.001, cluster size>50, uncorrected).3. PT changes of healthy side:Compared to control group, we found no significantly changes of diffusion indices in contralesional PT across time points, suggesting there was no detectable changes in the contralesional PT.4. PT changes in ipsilesional side:(1) The whole changes of PT:The rFA and rλ||of ipsilesional PT in the infarct site are lowest, the farther from the infarct site, the higher the indices. rMD and rλ⊥in the infarct site are highest, the farther from the infarct site, the lower the indices.The trend of5time points is relatively consistent.(2) The dynamic changes in infarct side:The rFA were decreased within first month, slightly increased from1months to3months, and then remained stable; The rMD did not change significantly within the first2weeks, increased from2weeks to1months, and then reached a relatively stable state. The rλ||(did not change significantly within the first2weeks, the increased gradully. The rλ⊥did not change significantly within the first2weeks, increased from2week to1months, then decreased after1months.(3) The dynamic changes above infarct side:The rFA in the first2weeks did not change significantly, decreased from2weeks to3months, then did not change significantly; The rMD did not changes significantly within the first2weeks, increased from2weeks to3months, then stay relatively stable. The rλ||did not change significantly within the first2weeks, the increased gradully. The rλ⊥did not change significantly within the first2weeks, increased from2weeks to3month, the decreased after3months.(4) The dynamic changes below infarct side:The rFA were decreased within first month, slightly increased from1months to3months, and then remained stable; The rMD and rλ⊥decreased within the first2weeks, then increased form2weeks to1months, the stay stable or slightly increased. The rλ⊥decreased within the first2weeks, increased from2to1months, the decreased to3months, and the increased after3months. 5.The correlation about changes between M1area GMV and PT:the ipsilesional M1area GMV was significantly negatively correlate to rFA and was opsitibely correlate to rMD and rλ⊥, There was no corelationship between GMV and rrλ|.Conclusions:1. GMV decreases were found in ipsilesional M1area, and significantly changes within the first3months, the stabilized.2. Structure changes were found in ipsilesional PT with severest in the infarct site and stretched Anterogradely and retrogradely along the PT, the reached a relatively stable state.3. The dynamic changes over time in ipsilesional M1area GMV is apparently consistent to the DTI incidices of the ipsilesional PT, and the changes did not progressively develop but reached stable after3months.