Imaging Demyelination using MTR

Fjær S, Bø L, Lundervold A, Myhr KM, Pavlin T, Torkildsen O, Wergeland S.Deep Gray Matter Demyelination Detected by Magnetization Transfer Ratio in the Cuprizone Model. PLoS One. 2013;8(12):e84162.

In multiple sclerosis (MS), the correlation between lesion load on conventional magnetic resonance imaging (MRI) and clinical disability is weak. This clinico-radiological paradox might partly be due to the low sensitivity of conventional MRI to detect gray matter demyelination (or it might be that the not all the CNS is imaged). Magnetization transfer ratio (MTR) has previously been shown to detect white matter demyelination in mice. In this study, we investigated whether MTR can detect gray matter demyelination in cuprizone (a poison for oligodendrocytes in certain brain regions) exposed mice. A total of 54 female C57BL/6 mice were split into one control group and eight cuprizone exposed groups. The mice were exposed to cuprizone for up to six weeks. MTR images were obtained at a 7 Tesla MR-scanner before cuprizone exposure, weekly for six weeks during cuprizone exposure, and once two weeks after termination of cuprizone exposure. Immunohistochemistry staining for myelin (anti-Proteolipid Protein) and oligodendrocytes (anti-Neurite Outgrowth Inhibitor Protein A) was obtained after each weekly scanning. Rates of MTR change and correlations between MTR values and histological findings were calculated in five brain regions. In the corpus callosum and the deep gray matter a significant rate of MTR value decrease was found. The MTR values correlated to myelin loss as evaluated by immunohistochemistry (Corpus callosum and Deep gray matter), but did not correlate to oligodendrocyte density. Significant results were not found in the cerebellum, the olfactory bulb or the cerebral cortex. This study shows that MTR can be used to detect demyelination in the deep gray matter, which is of particular interest for imaging of patients with MS, as deep gray matter demyelination is common in MS, and is not easily detected on conventional clinical MRI.

Can you see the changes in the corpus callosum

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