1,721,043 research outputs found
Functional brain reorganization in multiple sclerosis: Evidence from fMRI studies
No full textIn patients with multiple sclerosis (MS), the severity of clinical signs is not closely related to indices of structural brain damage provided by conventional magnetic resonance MR. Accordingly, patients with MS may show symptom recovery while progressively accumulating tissue damage. Changes in functional organization of the cerebral cortex have been reported in functional magnetic resonance (fMRI) studies that have compared the activation patterns during motor, visual, and cognitive tasks of patients with MS with those of healthy controls. fMRI studies on MS have provided the results that are difficult to compare and may be discrepant because of differences in the criteria used for patient selection, the activation paradigm, the experimental design, and the MR acquisition parameters. Nevertheless, they do provide a new, interesting tool that sheds light on how the brain changes its functional organization in response to MS. In patients with MS, functional brain reorganization mainly consists of an increase in the extent of activation of the brain areas used by healthy subjects, as well as the recruitment of additional brain areas. These findings have been interpreted as adaptive or compensatory mechanisms that allow normal performance despite neural damage or loss. However, brain functional activity may also change in response to clinical disability, though the precise role of brain functional changes in MS has yet to fully undersand. Longitudinal studies designed to explore the effects of both rehabilitation and pharmacological agents on brain plasticity might shed light on this issue
The role of MRI in dementia.
No full textReview. Neuroimaging techniques aimed at studying structural changes of the brain may provide useful information for the diagnosis and the clinical management of patients with dementia. Magnetic resonance imaging (MRI) may show abnormalities amenable to surgical treatment in a significant percentage of patients with cognitive impairment. MRI may also assist the differential diagnosis in dementia associated with metabolic or inflammatory diseases.MRI has the potential to detect focal signal abnormalities which may assist the clinical differentiation between Alzheimer's disease (AD) and vascular dementia (VaD). Severe temporal atrophy, hyperintensities involving the hippocampal or insular cortex, and gyral hypointense bands are more frequently noted in AD. Basal ganglionic/thalamic hyperintense foci, thromboembolic infarctions, confluent white matter and irregular periventricular hyperintensities are more common in VaD. The high sensitivity of MRI in detecting T2 hyperintense lesions and the low specificity off white matter lesions have resulted in a poor correlation between MRI findings and both neuropathological and clinical manifestations. In particular, MRI has disclosed a series of white matter focal changes in the elderly population, which are not necessarily associated with cognitive dysfunction. The recent advent of a new MRI method sensitive to the microstructural changes of white matter, the so-called diffusion tensor imaging, may be helpful in correlating clinical manifestations with white matter abnormalities
Brain reorganization during attention and memory tasks in multiple sclerosis:insights from functional MRI studies.
No full textDeficits in memory and attention frequently occur during the course of multiple sclerosis (MS). In patients with MS the severity of cognitive manifestations is not closely related to indices of structural brain damage on both conventional and non conventional magnetic resonance imaging (MRI). It is conceivable that the ability of the brain to compensate for tissue impairment or loss may contribute to the maintenance of normal performance despite scattered brain lesions. Accordingly, using functional MRI (fMRI), patients with multiple sclerosis showed a greater extent of brain activation during motors tasks than controls. Changes in functional organization of the cerebral cortex have also been reported by fMRI studies comparing the activation patterns during cognitive tasks in patients with MS and in healthy subjects. Differences in patients’ selection, activation paradigm, experimental design and MR acquisition parameters make, however, the results obtained from fMRI studies difficult to be compared and may explain, at least partially, some discrepant findings. Nevertheless, fMRI studies provide a new interesting way of understanding how the brain can change its functional organization in response to MS pathology, and might be useful in the study of the effects of either rehabilitation or pharmacological agents on brain plasticity. D 2006 Elsevier B.V. All rights reserved
Differential diagnosis of brain tumor and brain abscess with diffusion MR. Report of 2 cases and review of the literature
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