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Remyelinated lesions in multiple sclerosis: magnetic resonance image appearance
Frederik Barkhof1, Wolfgang Bruck, Corline J A De Groot
1Dutch MR-MS Center, and Department of Radiology, Vrije Universiteit Medical Center, PO Box 7057, 1007 MB Amsterdam, the Netherlands. f.barkhof@vumc.nl
Background:
Various types of pathologic mechanisms in multiple sclerosis (MS) can alter magnetic resonance imaging (MRI) signals, and the appearance of remyelinated lesions on MRI is largely unknown.
Objective:
To describe the MRI appearance of remyelinated lesions in MS.
Design:
Comparison of postmortem MRI findings with histopathologic findings.
Setting:
Brain donations from a general community. Patients Magnetic resonance images from 36 rapid autopsies yielded 161 areas that could be matched with histologic characteristics, including 149 focal T2-weighted abnormalities, with a range of signal intensities on T1-weighted images. In a subset of 49 lesions, magnetization transfer ratio could be determined.
Main Outcome Measures:
An observer blinded to the MRI findings assessed the presence of remyelination using light microscopic criteria; in 25 areas, in situ hybridization was used to assess the presence of oligodendrocytes expressing proteolipid protein messenger RNA.
Results:
Remyelinated areas were found in 67 lesions (42%): partial remyelination was present in 30 lesions (19%), whereas 37 lesions (23%) were fully remyelinated. Remyelinated lesions contained enhanced numbers of oligodendrocytes containing proteolipid protein messenger RNA. All areas with remyelination shown histopathologically were hyperintense on T2-weighted images. Strong hypointensity on T1-weighted images was significantly associated (chi2 = 29.8, P<.001) with demyelinated and partially remyelinated lesions compared with fully remyelinated lesions. The magnetization transfer ratio of remyelinated lesions (mean [SD], 27.6% [41%]) differed (F = 46.3, P<.001) from both normal-appearing white matter (35.2% [32%]) and demyelinated lesions (22.3% [48%]).
Conclusions:
Remyelinated lesions return an abnormal signal on T2-weighted images. Both T1-weighted images and magnetization transfer ratio may have (limited) additional value in separating lesions with and without remyelination.
Insights
Remyelinated lesions in multiple sclerosis (MS) show abnormal T2-weighted MRI signals. T1-weighted imaging and magnetization transfer ratio offer limited value in distinguishing remyelinated from demyelinated lesions.
Area of Science:
- Neuroimaging
- Pathology
- Multiple Sclerosis Research
Background:
- Pathologic mechanisms in multiple sclerosis (MS) alter magnetic resonance imaging (MRI) signals.
- The MRI appearance of remyelinated lesions in MS is not well understood.
Purpose of the Study:
- To characterize the MRI appearance of remyelinated lesions in multiple sclerosis.
- To correlate histopathologic findings with postmortem MRI.
Main Methods:
- Postmortem MRI findings were compared with histopathologic data from 36 rapid autopsies.
- 161 areas were matched, including 149 T2-weighted abnormalities, with assessment of T1-weighted signal intensity and magnetization transfer ratio in a subset.
- Remyelination was assessed using light microscopy and in situ hybridization for oligodendrocyte markers.
Main Results:
- 42% of lesions (67/161) showed evidence of remyelination (partial or full).
- Remyelinated lesions were hyperintense on T2-weighted images.
- T1-weighted hypointensity was associated with demyelinated/partially remyelinated lesions (P<.001); magnetization transfer ratio differed between remyelinated, demyelinated, and normal-appearing white matter (P<.001).
Conclusions:
- Remyelinated lesions exhibit abnormal T2-weighted MRI signals.
- T1-weighted imaging and magnetization transfer ratio may provide limited additional information for differentiating remyelinated lesions.