Although MS has been traditionally considered as an inflammatory-demyelinating disease of the white matter (WM) of the brain and spinal cord, an increasing number of studies have demonstrated that the grey matter (GM) is also a major player in this disease. However, the MRI techniques currently used in clinical practice are not able to detect to what extent the GM is damaged in MS. In this article the authors show that very high field MRI techniques enable detection of not only cortical GM lesions, but also myelin content and neuronal density, in post-mortem MS brain, very accurately. This study represents a breakthrough in the study of the brain in MS by MRI techniques. Brain. 2010 Jan 31 (epub ahead of print)
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Multiple sclerosis is an inflammatory, degenerative disease of the central nervous system. The most obvious pathological change in multiple sclerosis is multifocal demyelination of the white matter, but grey matter demyelination may be of equal or even greater importance for its clinical manifestations. In order to assess the pathogenetic role of lesions in the grey and white matter, and to explore the association between demyelinated and non-lesional brain tissue, tools are needed to depict each of these tissue components accurately in vivo.
Due to its sensitivity in detecting white matter lesions, T(2)-weighted magnetic resonance imaging at 1.5 T is important in the diagnosis of multiple sclerosis. However, magnetic resonance imaging at 1.5 T largely fails to detect grey matter lesions. In this study, T(2)-weighted magnetic resonance imaging at 9.4 T was used to detect grey matter lesions in fixed post-mortem multiple sclerosis motor cortex. Study authors produced T(1), T(2) and magnetization transfer ratio maps, and correlated these indices with quantitative histology [neuronal density, intensity of immunostaining for myelin basic protein (reflecting myelin content) and phosphorylated neurofilament (reflecting axonal area)] using t-tests and multivariate regression. Data compiled reveals that T(2)-weighted magnetic resonance imaging at 9.4 T enables detection of cortical grey matter lesion in post-mortem multiple sclerosis brain. The quantitative associations suggest that in cortical grey matter T(1) may be a predictor of neuronal density, and T(2) of myelin content (and-secondarily-axons). Successful translation of these results into in vivo studies using high field magnetic resonance imaging (e.g. 3 T and 7 T) may improve the assessment of cortical pathology and having an impact on the diagnosis and natural history studies of patients with multiple sclerosis, as well as clinical trial designs for proposed treatments to prevent cortical demyelination and neuronal loss.
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