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.
"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). "
[Show abstract][Hide abstract] ABSTRACT: Objectives: Contralesional brain connectivity plasticity was previously reported after stroke. This study aims at disentangling the biological mechanisms underlying connectivity plasticity in the uninjured motor network after an ischemic lesion. In particular, we measured generalized fractional anisotropy (GFA) and magnetization transfer ratio (MTR) to assess whether post-stroke connectivity remodeling depend on axonal and/or myelin changes. Materials and Methods: Diffusion Spectrum Imaging (DSI) and Magnetization Transfer MRI at 3T were performed in 10 patients in acute phase, at one and six months after stroke, which was affecting motor cortical and/or subcortical areas. Ten age- and gender- matched healthy volunteers were scanned one month apart for longitudinal comparison. Clinical assessment was also performed in patients prior to MRI. In the contra-lesional hemisphere, average measures and tract-based quantitative analysis of GFA and MTR was performed to assess axonal integrity and myelination along motor connections as well as their variations in time. Results and Conclusions: Mean and tract-based measures of MTR and GFA showed significant changes in a number of contralesional motor connections, confirming both axonal and myelin plasticity in our cohort of patients. Moreover, density-derived features (peak height, standard deviation-SD and skewness) of GFA and MTR along the tracts showed additional correlation with clinical scores than mean values. These findings reveal the interplay between contralateral myelin and axonal remodeling after stroke.
[Show abstract][Hide abstract] ABSTRACT: This chapter provides an overview on the use of Virtual Reality (VR) in rehabilitation with respect to recent neuroscience and physical therapy reviews of individuals with motor impairments. A wide range of technologies have been employed to provide rehabilitation supported by VR. Several studies have found evidence of the benefits of VR rehabilitation technologies. However, support for their efficacy is still limited due the lack of generalizable results and the uncoordinated effort of many individual, heterogeneous studies that have been conducted. Although VR has clear potential as a rehabilitation tool to improve treatment outcomes, future trials need to take into account the individual perspective of each patient group and consolidate research methodologies across trials to allow for stronger conclusions across the heterogeneous field of neurorehabilitation.
Emerging Therapies in Neurorehabilitation, Edited by Jose L Pons, Diego Torricelli, 01/2014: chapter 13 - Virtual Reality: pages 249-265; Springer., ISBN: 978-3-642-38555-1 (Print) 978-3-642-38556-8 (Online)
[Show abstract][Hide abstract] ABSTRACT: Cerebral ischemia manifests widely in patient symptoms. Along with the clinical examination, imaging serves as a powerful tool throughout the course of ischemia-from acute onset to evolution. A thorough understanding of imaging modalities, their strengths and their limitations, is essential for capitalizing on the benefit of this complementary source of information for understanding the mechanism of disease, making therapeutic decisions, and monitoring patient response over time.
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