Abstract
In multiple sclerosis (MS), a histopathological distinction is made between different stages of white matter (WM) lesions. These lesions are characterized as preactive, active, chronic active or chronic inactive, depending on the degree of microglia activation and degree of demyelination. The different lesions are not distinguishable on conventional magnetic resonance imaging (MRI) scans at standard clinical field strengths, but might be distinguished using more advanced, quantitative MRI methods, such as T1 relaxation time (T1-RT) mapping. To investigate this, postmortem brain material from 20 MS patients was investigated, using both T1-RT MRI at 1.5T and histopathology. The brain material contained a total of 9 preactive, 18 active, 30 chronic active and 14 chronic inactive lesions, as well as 38 areas of normal appearing WM (NAWM). Our results show that, at 1.5T, T1-RT qMRI can only distinguish between categories NAWM/preactive, active and chronic WM lesions. Advanced imaging at standard field strengths, such as conventional imaging measures, is therefore insufficient to differentiate the WM lesions in MS, and higher field strengths may be required to achieve better pathological differentiation of these lesions.
Highlights
Multiple sclerosis (MS) is an inflammatory and demyelinating disease of the central nervous system (CNS)
At 1.5T, T1 relaxation time (T1-relaxation time (RT)) Quantitative MRI (qMRI) can only distinguish between categories normal appearing WM (NAWM)/preactive, active and chronic white matter (WM) lesions
Statistical analysis of T1-RT revealed that NAWM differed significantly from active, chronic active and chronic inactive lesion types
Summary
Multiple sclerosis (MS) is an inflammatory and demyelinating disease of the central nervous system (CNS). A distinction can be made between different stages of white matter (WM) lesions that may be characterized as preactive, active, chronic active or chronic inactive, depending on their degree of microglia activation, adaptive immune response and demyelination [1]. Preactive lesions still have normal myelin density and morphology, but already show clusters of activated microglia. There is complete demyelination; microglia and macrophages are no longer present. For clinical purposes, it would be extremely useful if this pathological distinction could be made in vivo. This way, an inflammatory profile of MS patients could be more accurately described; the clinical impact of these different lesion stages, as well as their development over time, their occurrence in different patient and disease stages and their responsiveness to therapy could be monitored.
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