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

ABSTRACT 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.

  • Source
    [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.
    10/2014; DOI:10.1089/brain.2014.0245
  • [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.
    Neurologic Clinics 02/2014; 32(1):193-209. DOI:10.1016/j.ncl.2013.07.005 · 1.61 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Background Recent studies show neuroprotective benefits of isoflurane (ISO) administered during cerebral ischemia. However, the available studies evaluated cerebral injury only at a single time point following the intervention and thus the longitudinal effect of ISO on ischemic tissues remains to be investigated. Objective The objective of the present study is to investigate the longitudinal effect of ISO treatment in counteracting the deleterious effect of ischemia by evoking the transcription factor, hypoxia inducible factor-1 (HIF-1), and vascular endothelial growth factor (VEGF). Methods Focal cerebral ischemia was induced in 70 rats by filament medial cerebral artery occlusion (MCAo) method. MCAo rats were randomly assigned to control (90 min ischemia) and MCAo+ISO (90 min ischemia +2% ISO) groups. Infarct volume, edema, intracerebral hemorrhage (ICH) and regional cerebral blood flow (rCBF) were measured in 8 in vivo sequential MR imaging sessions for 3 weeks. Western blot analysis and immunofluorescence were used to determine the expression level of HIF-1α (the regulatable subunit of HIF-1) and VEGF proteins. Results ISO inhalation during ischemia significantly decreased the surge of infarct volume, edema, ICH, and reduced the mortality rate (p<0.01). ISO transiently altered the rCBF, significantly enhanced the expression of HIF-1α and VEGF and decreased the immune cell infiltration. Locomotor dysfunction was ameliorated at a significantly faster pace, and the benefit was seen to persist up to three weeks. Conclusion Treatment with ISO during ischemia limits the deadly surge in the dynamics of ischemia reperfusion injury with no observed long term inverse effect.
    Brain Research 10/2014; 1586. DOI:10.1016/j.brainres.2014.08.003 · 2.83 Impact Factor