Elevations of diffusion anisotropy are associated with hyper-acute stroke: a serial imaging study

Diffusion tensor imaging (DTI) studies of human ischemic stroke within 24 h of symptom onset have reported variable findings of changes in diffusion anisotropy. Serial DTI within 24 h may clarify these heterogeneous results. We characterized longitudinal changes of diffusion anisotropy by analyzing discrete ischemic white matter (WM) and gray matter (GM) regions during the hyperacute (2.5-7 h) and acute (21.5-29 h) scanning phases of ischemic stroke onset in 13 patients. Mean diffusivity (MD), fractional anisotropy (FA) and T2-weighted signal intensity were measured for deep and subcortical WM and deep and cortical GM areas in lesions outlined by a >= 30% decrease in MD. Average reductions of similar to 40% in relative (r) MD were observed in all four brain regions during both the hyperacute and acute phases post stroke. Overall, 9 of 13 patients within 7 h post symptom onset showed elevated FA in at least one of the four tissues, and within the same cohort, I I of 13 patients showed reduced FA in at least one of the ischemic WM and GM regions at 21.5-29 It after stroke. The fractional anisotropy in the lesion relative to the contralateral side (rFA, mean +/- S.D.) was significantly elevated in some patients in the deep WM (1.10 +/- 0.11, n=4), subcortical WM (1.13 +/- 0.14, n=4), deep GM (1.07 +/- 0.06, n=1) and cortical GM (1.22 +/- 0.13, n=5) hyperacutely (<= 7 h); however, reductions of rFA at similar to 24 It post stroke were more consistent (rFA=0.85 +/- 0.12). (C) 2008 Elsevier Inc. All rights reserved.