Diffusion Tensor Imaging Shows Structural Remodeling of Stroke Mirror Region: Results from a Pilot Study

Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA, USA.
European Neurology (Impact Factor: 1.36). 05/2012; 67(6):370-6. DOI: 10.1159/000336062
Source: PubMed


The role of the non-injured hemisphere in stroke recovery is poorly understood. In this pilot study, we sought to explore the presence of structural changes detectable by diffusion tensor imaging (DTI) in the contralesional hemispheres of patients who recovered well from ischemic stroke.
We analyzed serial DTI data from 16 stroke patients who had moderate initial neurological deficits (NIHSS scores 3-12) and good functional outcome at 3-6 months (NIHSS score 0 or modified Rankin Score ≤1). We segmented the brain tissue in gray and white matter (GM and WM) and measured the apparent diffusion coefficient (ADC) and fractional anisotropy in the infarct, in the contralesional infarct mirror region as well as in concentrically expanding regions around them.
We found that GM and WM ADC significantly increased in the infarct region (p < 0.01) from acute to chronic time points, whereas in the infarct mirror region, GM and WM ADC increased (p < 0.01) and WM fractional anisotropy decreased (p < 0.05). No significant changes were detected in other regions.
DTI-based metrics are sensitive to regional structural changes in the contralesional hemisphere during stroke recovery. Prospective studies in larger cohorts with varying levels of recovery are needed to confirm our findings.

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    • "onnectivity remodeling after stroke has been reported in both injured (Sotak, 2002) and uninjured hemispheres (Carmichael et al., 2001; Chollet et al., 1991; Granziera et al., 2007; Jones et al., 1996; Luke et al., 2004; Rehme et al., 2011; Riecker et al., 2010; Takatsuru et al., 2009; Weiller et al., 1992, 1993). Diffusion magnetic resonance imaging (dMRI) studies showed contralesional changes in scalar measures as mean fractional anisotropy (FA) and apparent diffusion coefficient (Granziera et al., 2012a, Ozsunar et al., 2004); on the other hand, tractography-based dMRI investigations revealed a variable increase or decrease in average number/density/ probability of fiber trajectories (Crofts et al., 2011; Granziera et al., 2012b). Despite these average measures indicate the presence and the degree of contralesional axonal remodeling, they fail in providing detailed information about the nature of the underlying pathological process (i.e., myelin or axonal plasticity) (Alexander et al., 2007; Beaulieu, 2006). "
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