Structural integrity of the contralesional hemisphere predicts cognitive impairment in ischemic stroke at three months

Abstract

After stroke, white matter integrity can be affected both locally and distally to the primary lesion location. It has been shown that tract disruption in mirror's regions of the contralateral hemisphere is associated with degree of functional impairment. Fourteen patients suffering right hemispheric focal stroke (S) and eighteen healthy controls (HC) underwent Diffusion Weighted Imaging (DWI) and neuropsychological assessment. The stroke patient group was divided into poor (SP; n = 8) and good (SG; n = 6) cognitive recovery groups according to their cognitive improvement from the acute phase (72 hours after stroke) to the subacute phase (3 months post-stroke). Whole-brain DWI data analysis was performed by computing Diffusion Tensor Imaging (DTI) followed by Tract Based Spatial Statistics (TBSS). Assessment of effects was obtained computing the correlation of the projections on TBSS skeleton of Fractional Anisotropy (FA) and Radial Diffusivity (RD) with cognitive test results. Significant decrease of FA was found only in right brain anatomical areas for the S group when compared to the HC group. Analyzed separately, stroke patients with poor cognitive recovery showed additional significant FA decrease in several left hemisphere regions; whereas SG patients showed significant decrease only in the left genu of corpus callosum when compared to the HC. For the SG group, whole brain analysis revealed significant correlation between the performance in the Semantic Fluency test and the FA in the right hemisphere as well as between the performance in the Grooved Pegboard Test (GPT) and the Trail Making Test-part A and the FA in the left hemisphere. For the SP group, correlation analysis revealed significant correlation between the performance in the GPT and the FA in the right hemisphere.

Figure 1. Significant changes in FA for the stroke group with poor recovery (SP) and the stroke group with good recovery (SG) at 3 months when compared with healthy controls (HC).

The red color identifies clusters with significant decrease of FA. Statistical maps are represented in radiological convention (right corresponds to left hemisphere), superimposed on an MNI152 template. The threshold for significance was set at p≤0.02 corrected for multiple comparisons. Circles highlight the locus of clusters in the HC>SP contrasts not found in the HC> SG contrast.

Figure 2. Significant changes in FA and RD for the stroke group with poor recovery at 3 months when compared with healthy controls.

The red and blue colors show clusters of significant decrease of FA and increase of RD. Statistical maps are represented in radiological convention (right corresponds to left hemisphere) and are displayed superimposed on an MNI152 template. The threshold for significance was set at p≤0.02 corrected for multiple comparisons.