Leukoaraiosis, ischemic stroke, and normal white matter on diffusion-weighted MRI.

BACKGROUND AND PURPOSE Leukoaraiosis is a radiological finding of uncertain pathogenesis with bilateral patchy or diffuse areas of hyperintensity of the cerebral white matter (WM) on T2-weighted MRI. Using diffusion-weighted MRI (DWI), we aimed to test (1) whether the average apparent diffusion coefficient (ADC(av)) values of the regions of leukoaraiosis vary according to the degree of the severity of leukoaraiosis and whether the regions of leukoaraiosis could be distinguished (2) from normal WM or (3) from ischemic strokes of various ages. METHODS We compared 85 patients with leukoaraiosis, 22 healthy subjects with no leukoaraiosis on the conventional MR images, and 10 patients with ischemic strokes serially imaged <6 hours, 24 hours, 1 week, 1 month, and 3 months after stroke onset. All subjects were studied with DWI in 3 orthogonal directions with 2 b values (b=0 and b=1000 s/mm(2)) at 1.5 T. ADC(av) values were determined for the regions of leukoaraiosis, ischemic lesions, and normal WM. RESULTS The more severe the leukoaraiosis was, the higher the ADC(av) values of the leukoaraiotic regions became. The ADC(av) values (in 10(-3) mm(2)/s) of the regions of leukoaraiosis (0.92 to 1.27) were significantly higher than that of the normal WM (0.69+/-0.04) and that of the ischemic strokes at 6 hours (0.38+/-0.07), 24 hours (0.36+/-0.10), and 1 week (0.51+/-0.09). One-month-old ischemic strokes (1.08+/-0.33) had ADC(av) values similar to those of leukoaraiotic regions, whereas 3-month-old infarcts (1.59+/-0.32) showed significantly higher ADC(av) values than the leukoaraiotic regions. CONCLUSIONS The regions of leukoaraiosis show characteristic changes in ADC(av) values, and DWI can be used to differentiate acute and chronic ischemic stroke lesions from leukoaraiosis.