Abnormal Organization of White Matter Network in Patients with No Dementia after Ischemic Stroke

Abstract

Structural changes after ischemic stroke could affect information communication extensively in the brain network. It is likely that the defects in the white matter (WM) network play a key role in information interchange. In this study, we used graph theoretical analysis to examine potential organization alteration in the WM network architecture derived from diffusion tensor images from subjects with no dementia and experienced stroke in the past 5.4–14.8 months (N = 47, Mini-Mental Screening Examination, MMSE range 18–30), compared with a normal control group with 44 age and gender-matched healthy volunteers (MMSE range 26–30). Region-wise connectivity was derived from fiber connection density of 90 different cortical and subcortical parcellations across the whole brain. Both normal controls and patients with chronic stroke exhibited efficient small-world properties in their WM structural networks. Compared with normal controls, topological efficiency was basically unaltered in the patients with chronic stroke, as reflected by unchanged local and global clustering coefficient, characteristic path length, and regional efficiency. No significant difference in hub distribution was found between normal control and patient groups. Patients with chronic stroke, however, were found to have reduced betweenness centrality and predominantly located in the orbitofrontal cortex, whereas increased betweenness centrality and vulnerability were observed in parietal-occipital cortex. The National Institutes of Health Stroke Scale (NIHSS) score of patient is correlated with the betweenness centrality of right pallidum and local clustering coefficient of left superior occipital gyrus. Our findings suggest that patients with chronic stroke still exhibit efficient small-world organization and unaltered topological efficiency, with altered topology at orbitofrontal cortex and parietal-occipital cortex in the overall structural network. Findings from this study could help in understanding the mechanism of cognitive impairment and functional compensation occurred in patients with chronic stroke.

Altered Brain Structural Networks in Patients with Brain Arteriovenous Malformations Located in Broca’s Area

“…A small-world network can promote both segregated and integrated information processing, which is considered optimal compromise between regular and random networks [ 37 ]. In consistent with the past studies of stroke and tumors [ 20 , 22 ], the current patient series exhibited small-world organization of brain structural networks, suggesting that the brain harboring AVMs supports efficient parallel information processing at a minimal cost. Although the small-worldness of the two groups was comparable, the patients exhibited significantly decreased clustering coefficient and increased characteristic path length.…”

Risk Factors and Cognitive Relevance of Cortical Cerebral Microinfarcts in Patients With Ischemic Stroke or Transient Ischemic Attack

“…18 Infarcts were manually segmented on the DWI sequence by a technical expert with relevant clinical background. 19 All ratings were performed blind to patients' clinical data.…”

Homeostatic structural plasticity can account for topology changes following deafferentation and focal stroke

“…However, not the entire brain changes its topology but only those regions directly connected to the primary lesion site (Carmichael et al, 2001 ; Dancause et al, 2005 ; Rehme and Grefkes, 2013 ). Provided that connected brain regions become deafferentated by the primary lesion site, homeostatic structural plasticity, as revealed by our modeling study, may account for the observed changes in macroscopic topology after a lesion, i.e., an increased randomness of network connectivity and an increased or decreased betweenness centrality of particular regions (Wang et al, 2010 ; Shi et al, 2013 ). Wang et al ( 2010 ) reported an increase in betweenness centrality of brain regions that became deafferentated by a subcortical stroke, namely the ipsilesional primary motor area and the contralesional cerebellum.…”