FMRI Study Of Lesion Sites Related Cerebral Structure And Functional Connectivity Changes In Patients With Stroke

Objective:To investigate the neural mechanisms of motor recovery in different locations of cerebral infarction, we explored the correlation between the changes of brain structure and function within motor cortex by voxel-based morphometry (VBM) analysis and resting-state functional connectivity (rsFC) fMRI in chronic basal ganglia stroke patients and pontine stroke patients.Methods:Twenty-eight stroke patients with unilateral infarction of basal ganglia area and sixteen stroke patients with unilateral infarction of pontine area were separately compared with twenty-five age-and sex-matched healthy participants. GE3.0T HDX MR Scanner with a8-channel head coil was used to obtain high resolutions anatomy images and rs-fMRI data. The VBM analysis was calculated by the SPM8(http://www.fil.ion.ucl.ac.uk/spm). The comparison of gray matter volumn was performed in the whole brain level. Multiple comparisons were corrected by Monte Carlo simulation. The preprocessing of rs-fMRI data was carried out by the REST software. We defined the areas which were significantly different in gray matter volumn as ROIs. ROIs-based rsFC analysis was performed to calculate the functional connectivity maps of ROIs in the whole brain level using the REST software. The group comparison of functional connectivity maps was performed by two-sample t-test in SPM8. Multiple comparisons were corrected by Monte Carlo simulation.Results:Decreased gray matter volumn in ipsilesional primary motor area and ipsilensional thalamus was detected in basal ganglia stroke patients. The functional connectivity of ipsilensional primary motor area increased with itself. However, they are not completely overlapped. The area in which functional connectivity increased located in dorsomedial area of the impaired structure. The grey matter decreased in bilateral cerebellum posterior lobe, mainly in contralesional cerebellum while the gray matter volume was significantly increased in contralesional primary motor area and bilateral supplementary motor area in pontine stroke patients. The functional connectivity of contralesional cerebellum posterior lobe increased with bilateral supplementary motor area and contralesional premotor cortex. The contralesional primary motor area exhibited higher functional connectivity with contralesional premotor cortex while decreased functional connectivity with contralesional cerebellum posterior lobe. The bilateral supplementary motor area showed higher functional connectivity with contralesioinal postcentral gyrus and bilateral cerebellum anterior lobe.Conclusions:1. Impaired structures distal to the primary lesion were detected both in chronic basal ganglia stroke patients and pontine stroke patients. However, the location of structural damage was different:in basal ganglia stroke patients, the damaged structures were ipsilesional primary motor area and ipsilensional thalamus while the damaged structures of pontine stroke patients were mainly located in contralesional cerebellum. Secondary degeneration of the axon may be the main reason for structural damage.2. Damaged structures were different between basal ganglia stroke patients and pontine stroke patients, as well as the areas with functional compensation. The functional connectivity of ipsilensional primary motor area increased with itself which play a role in functional compensation in basal ganglia stroke patients. However, they are not completely overlapped. The area with functional compensation was closer to sensory cortex. Nevertheless, in pontine stroke patients, bilateral supplementary motor area and contralesional premotor cortex play a role in functional compensation.3. The gray matter volumn of contralesional primary motor area and bilateral supplementary motor area increased in pontine stroke patients, which maybe play a role in structural compensation. Meanwhile, it was not similar in basal ganglia stroke patients. The conflicting results may have arisen from analyses at different lesion, the degree of damage and therapies.