BACKGROUND AND PURPOSE: Previous studies have shown that lesions in posterior reversible @entity75 syndrome are often isointense on diffusion-weighted MR images. We hypothesized that 1) apparent diffusion coefficient (ADC) maps using various thresholds would show @entity62 (WM) and 2) isointense appearance of lesions on isotropic diffusion-weighted images results from a balance of T2 prolongation effects and diffusibility effects. METHODS: T2-weighted MR images from 11 @entity1 were reviewed. Hyperintense lesions were located in both anterior and posterior WM in eight @entity1 and solely in posterior WM in three @entity1 . The ADC maps were produced by use of ADC values > or = 3 SD and > or = 10 SD above the mean value of normal WM. Lesions on diffusion-weighted images were classified as isointense or hypointense. ADC values within lesions (ADC(L)) were compared with those of normal WM (ADC(N)), and compared for isointense lesions and hypointense lesions. RESULTS: The distribution of lesions with ADC values > or = 3 SD was essentially identical to that on T2-weighted images. Regions with ADC values > or = 10 SD were found in both anterior WM and posterior WM in two @entity1 and solely in posterior WM in nine @entity1 . On diffusion-weighted images, lesions appeared isointense in seven @entity1 and hypointense in four @entity1 . Mean ADC(L)/ADC(N) for all lesions was 1.81; for hypointense lesions, 2.30. CONCLUSION: Vasogenic @entity4 was more severe in posterior WM. Isointense lesions result from a balance of T2 effects and increased water diffusibility. Hypointense lesions have higher ADC values, which are not balanced by T2 effects.

Quantitative assessment of diffusion abnormalities in posterior reversible XXXX syndrome.

@entity75 :: ('MESH:D001927', 'Disease') :: ['encephalopathy'] @entity1 :: ('9606', 'Species') :: ['patients'] @entity62 :: ('MESH:D056784', 'Disease') :: ['larger abnormalities in posterior white matter'] @entity4 :: ('MESH:D004487', 'Disease') :: ['edema']
@entity75 :: (MESH:D001927,Disease) :: ['encephalopathy']
