Sometimes it is demyelination from BBB breakdown, other times it can by from destruction of the axons with demyelination following axonal loss.
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“Dirty-appearing white matter” (DAWM) in multiple sclerosis (MS) is defined as a region(s) with ill-defined borders of intermediate signal intensity between that of normal-appearing white matter (NAWM) and that of plaque on T2-weighted and proton density imaging....
Quantitatively, the change in MWF in DAWM most consistently correlated with the change in LFB staining. The findings of this preliminary study suggest that DAWM is characterized by loss of myelin phospholipids, detected by the short T2 component, and axonal reduction.
Journal of Neurology
Volume 255, Number 11, 1802-1811, DOI: 10.1007/s00415-008-0002-z
Dirty-appearing white matter in multiple sclerosis
Preliminary observations of myelin phospholipid and axonal loss
G. R. W. Moore, C. Laule, A. MacKay, E. Leung, D. K. B. Li, G. Zhao, A. L. Traboulsee and D. W. Paty
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Bob
Thanks, guys. Definitely something on my MRI that shows up in T2, Flair, Diffusion, and even T1(dark cloudiness in that case).
Bob-- wouldn't you think DAWM would be considered evidence of blood-brain barrier breakdown?
It is typically considered areas of the white matter with clusters of many small punctuate lesions that appears as "smokey or cloudy areas" on T2 weighted and FLAIR sequences. It occurs in MS and some other white matter diseases.
Bob
"Dirty-appearing white matter" (DAWM) in multiple sclerosis (MS) is defined as a region(s) with ill-defined borders of intermediate signal intensity between that of normal-appearing white matter (NAWM) and that of plaque on T(2)-weighted and proton density imaging.
http://www.ncbi.nlm.nih.gov/pubmed/18821049