Diffusion of water in large demyelinating lesions: a follow-up study

Abstract

We studied five patients with multiple sclerosis with one plaque of demyelination more than 2 cm in diameter, using conventional and diffusion-weighted MRI, soon after the onset of symptoms and over 1-36 months. The orientationally averaged diffusion coefficient <D> was increased in all the acute lesions, and increased further during follow-up in three. There was a strong correlation between <D> and the degree of low signal on T1-weighted images. The quantitative information provided by <D> allowed delineation of different diffusion patterns in large MS lesions, that may reflect heterogeneity of the anatomical substrate.

Reduced Diffusion in a Subset of Acute MS Lesions: A Serial Multiparametric MRI Study

“…Several reports have demonstrated increased ADC values both in acute contrast-enhancing and chronic MS lesions as well as in the NAWM, confirming that diffusion measurements are sensitive for detecting pathologic changes associated with states of increased water mobility. [3][4][5]8,18 In chronic MS lesions, the ADC increase is highly variable (most pronounced ADC increase in T1 hypointense lesions) and higher than that in NAWM; this finding confirms the concept that the severity of tissue matrix damage of MS lesions is heterogeneous. 8 It has been suggested that inflammatory vasogenic edema, axonal loss, and demyelination are the most likely pathologic substrates of increased ADC.…”

“…1 Two longitudinal studies that also used longer intervals between MRI examinations (minimum of 4 weeks) have observed increased ADC signal intensity in the lesions already at the first MRI. 5,6 We think that both patient selection and the time from symptom onset to the first MRI are important in this regard and that it might well be that the hyperacute phase was missed in these studies. Another cross-sectional study extrapolated different phases of lesion acuity by using DWI findings; however, this was done without the opportunity to ascertain DWI findings on serial analysis.…”

“…1,2 DWI investigates water mobility, which is increased in chronic lesions and in acute vasogenic edema in MS. [3][4][5] This increase is thought to reflect expanded extracellular space, even though the individual contributions from edema, demyelination, and axonal loss are yet unknown. [6][7][8] DWI also may detect reductions of normal water mobility, which is typically but not exclusively demonstrated in acute ischemic stroke.…”

“Dazed and diffused”: making sense of diffusion abnormalities in neurologic pathologies

“…Acute multiple sclerosis plaques typically demonstrate increased diffusion-weighted signal with increased ADC values [37,70,71]. As the plaques age, the ADC values decrease but remain elevated compared with normal white matter [72][73][74].…”

Neuroimaging Highlight - Diagnostic Considerations in Acute MS Lesions with Restricted Diffusion on MRI

“…This well recognized imaging pattern is felt to represent increased free water content due to vasogenic edema and demyelination. 1 Rarely, MS lesions have increased DWI and decreased ADC signal in the acute phase, a pattern that mimics the radiographic features of acute stroke. [2][3][4] Such diverse disorders as primary central nervous system lymphoma, abscess, hemorrhage, and post-stroke Wallerian-like degeneration can also have true restricted diffusion.…”