Structural and functional disconnections in non-acute post-stroke patients

Abstract

Background: Structural alterations and functional reorganizations related to motor dysfunction after stroke remain unclear. This study aims to investigate alterations in structural connectivity (SC) and functional connectivity (FC) in non-acute post-stroke patients, and their associations with motor performance.

Methods: Thirty-six non-acute post-stroke patients and thirty-eight well-matched healthy controls (HCs) were included. SC and FC differences between groups were analyzed using diffusion tensor imaging and resting-state fMRI, respectively. Correlations between SC and FC in regions with significant intergroup differences, along with their correlations with motor performance, were assessed.

Results: Compared with HCs, significant decreases in both SC and FC were observed in stroke patients among the right precentral gyrus, right superior frontal gyrus, right supplementary motor area, right paracentral lobule, right middle cingulate gyrus, right superior marginal gyrus, right middle temporal gyrus, and left inferior temporal gyrus. A negative correlation of SC-FC was found between the right middle cingulate gyrus and right paracentral lobule in stroke group, while a positive correlation was found between the right superior marginal gyrus and right middle temporal gyrus. Moreover, the FC between the right superior marginal gyrus and right middle temporal gyrus showed negative correlations with the Fugl-Meyer assessment of the Upper/Lower Extremity scores.

Discussion: This study identified disconnections in both SC and FC in sensorimotor-related and high-order brain regions, which may enhance understanding of the structure-function interactions underlying motor deficits in post-stroke patients.

Keywords: functional connectivity; magnetic resonance imaging; motor dysfunctions; stroke; structural connectivity.

Figure 1

The lesions of all the participants. The color bar represents the number of participants with stroke. (A) The left-sided lesions; (B) the right-sided lesions; (C) the overlapping of all lesions by mirroring the right-side lesions to the left side. L, left; R, right.

Figure 2

Connections showing significant alterations in SC alterations in stroke patients. A–E represents significant SC alterations in stroke patients between r_SFG and r_PreCG, between r_SMA and r_PCL, between r_PCL and r_MCG, between r_SMG and r_MTG, between l_MTG and l_ITG, respectively. ROI, region of interest; PreCG, precentral gyrus; SFG, superior frontal gyrus; SMA, supplementary motor area; PCL, paracentral lobule; SMG, superior marginal gyrus; MTG, middle temporal gyrus; ITG, inferior temporal gyrus; l, left; r, right. The number of connecting lines in the figure represents the strength of the structural connections; the color of the fiber bundle indicates the direction of fiber tract, where red represents fibers running left–right, green represents fibers running anterior–posterior, and blue represents fibers running superior–inferior.

Figure 3

The correlations between SC and FC in ROI-ROI with both SC and FC alterations in patient group. (A) Correlation between structural and functional connectivity between the right middle cingulate gyrus and the right paracentral lobule; (B) Correlation between structural and functional connectivity between the right supramarginal gyrus and the right middle temporal gyrus. SC_rMCG-rPCL, structural connectivity between the right middle cingulate gyrus and the right paracentral lobule; FC_rMCG-rPCL, functional connectivity between the right middle cingulate gyrus and the right paracentral lobule connections; SC_rSMG-rMTG, structural connections between the right superior marginal gyrus and the right middle temporal gyrus; FC_rSMG-rMTG, functional connections between the right superior marginal gyrus and the right middle temporal gyrus.

Figure 4

The FCs correlated with motor function in post-stroke patients. (A) Correlation between the FC_rSMG-rMTG and the motor function of the upper limb on the hemiplegic side; (B) Correlation between the FC_rSMG-rMTG and the motor function of the lower limb on the hemiplegic side. FC_rSMG-rMTG, Functional connectivity between the right superior marginal gyrus and the right middle temporal gyrus; FMA-UE, the Fugl-Meyer Assessment of Upper Extremity; FMA-LE, the Fugl-Meyer Assessment of Lower Extremity; ROI, region of interest.