Article

Diffusion tensor imaging of time-dependent axonal and myelin degradation after corpus callosotomy in epilepsy patients.

Department of Biomedical Engineering, Faculty of Medicine and Dentistry, 1098 Research Transition Facility, University of Alberta, Edmonton, Alberta, Canada T6G 2V2.
NeuroImage (Impact Factor: 6.25). 10/2006; 32(3):1090-9. DOI: 10.1016/j.neuroimage.2006.04.187
Source: PubMed

ABSTRACT Axonal degeneration of white matter fibers is a key consequence of neuronal or axonal injury. It is characterized by a series of time-related events with initial axonal membrane collapse followed by myelin degradation being its major hallmarks. Standard imaging cannot differentiate these phenomena, which would be useful for clinical investigations of degeneration, regeneration and plasticity. Animal models suggest that diffusion tensor magnetic resonance imaging (DTI) is capable of making such distinction. The applicability of this technique in humans would permit inferences on white matter microanatomy using a non-invasive technique. The surgical bisection of the anterior 2/3 of the corpus callosum for the palliative treatment of certain types of epilepsy serves as a unique opportunity to assess this method in humans. DTI was performed on three epilepsy patients before corpus callosotomy and at two time points (1 week and 2-4 months) after surgery. Tractography was used to define voxels of interest for analysis of mean diffusivity, fractional anisotropy and eigenvalues. Diffusion anisotropy was reduced in a spatially dependent manner in the genu and body of the corpus callosum at 1 week and remained low 2-4 months after the surgery. Decreased anisotropy at 1 week was due to a reduction in parallel diffusivity (consistent with axonal fragmentation), whereas at 2-4 months, it was due to an increase in perpendicular diffusivity (consistent with myelin degradation). DTI is capable of non-invasively detecting, staging and following the microstructural degradation of white matter following axonal injury.

0 Bookmarks
 · 
64 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Bipolar disorder is a severe, disabling and life-threatening illness, which affects nearly 2% of the general population. The identification of reliable and objective biomarkers may aid early diagnosis and optimize treatment efficacy. Through a careful overview of the neuroimaging studies which investigated the structural, functional, and effective connectivity in bipolar disorder, we explored the role of a disconnected cortico-limbic circuitry in the development and maintenance of the disorder. This review offers perspectives and suggestions for future research, in order to propose the corticolimbic disconnection as a neurobiological underpinning and biomarker for bipolar psychopathology.
    Expert Review of Neurotherapeutics 06/2014; 14(6):631-50. · 2.96 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This study investigated the clinical value of diffusion tensor imaging (DTI) in predicting the motor outcome in patients with basal ganglia hemorrhage. This prospective study included 23 patients assessed with DTI to measure the fractional anisotropy (FA) value in affected cortical spinal tract (CST) at three time points: day 0, day 30 and day 90 after onset. The motor function score (MFS) was applied to evaluate motor function and patients were divided into good and poor outcome groups according to the MFS on day 90. The mean FA value on day 0 was significantly lower in the poor outcome group than in the good outcome group (p<0.01). FA value gradually decreased in the poor outcome group until day 90 after onset, while it continuously increased in the good outcome group. The MFS obtained at day 90 after onset was significantly correlated with the initial FA value in the affected cerebral peduncle (r=-0.926, p<0.01). Receiver operating characteristic curve analysis showed that the FA value on day 0 could predict motor function outcome with a sensitivity of 88.89% and specificity of 92.86% at the initial FA value of 0.45. The FA value of affected CST in acute cerebral hemorrhage may valuably predict the motor function outcome and its dynamic change may represent the Wallerian degeneration in motor tracts after hemorrhagic stroke.
    Journal of Clinical Neuroscience 04/2014; · 1.25 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Depression is amongst the most debilitating diseases worldwide. Long term exposure to stressors plays major role in development of human depression. Chronic mild stress (CMS) seems to be a valid animal model for depression. Diffusion Tensor Imaging (DTI) is capable of inferring microstructural abnormalities of the white matter and has shown to serve as non-invasive marker of specific pathology. We developed a CMS rat model of depression and validated with behavioral experiments. We measured the diffusion indices (Mean Diffusivity (MD), Fractional Anisotropy (FA), axial (λ∥) and radial (λ⊥) diffusivity) to investigate the changes in CMS rat brain during depression onset. Diffusion indices have shown to be useful to discriminate myelin damage from axon loss. DTI was performed in both control and CMS rats (n=10, in each group) and maps of FA, MD, λ∥ and λ⊥ diffusivity values were generated using in house built software. The diffusion indices were calculated by ROI analysis in different brain regions like frontal cortex, hippocampus, hypothalamus, cingulum, thalamus, caudate putamen, corpus callosum, cerebral peduncle and sensory motor cortex. The results showed signs of demyelination, reflected by increased MD, decreased FA and increased λ⊥. The results also suggest a possible role of edema or inflammation concerning the brain morphology in CMS rats. The overall finding using DTI suggests there might be a major role of loss of myelin sheath, which leads to disrupted connectivity between the limbic area and the prefrontal cortex during the onset of depression. Our findings indicate that interpretation of these indices may provide crucial information about the type and severity of mood disorders.
    Neuroscience 05/2014; · 3.12 Impact Factor

Full-text

Download
32 Downloads
Available from
Jun 1, 2014