Reduction in cerebral blood flow in areas appearing as white matter hyperintensities on magnetic resonance imaging

Abstract

The purpose of this study was to examine cerebral blood flow (CBF) as measured by arterial spin labeling (ASL) in tissue classified as white matter hyperintensities (WMH), normal appearing white matter, and grey matter. Seventeen healthy older adults received structural and ASL MRI. Cerebral blood flow was derived for three tissue types: WMH, normal appearing white matter, and grey matter. Cerebral blood flow was lower in WMH areas relative to normal appearing white matter, which in turn, was lower than grey matter. Regions with consistently lower CBF across individuals were more likely to appear as WMH. Results are consistent with an emerging literature linking diminished regional perfusion with the risk of developing WMH.

Figure 1

Mean differences in CASL-determined blood flow in grey matter regions, normal appearing white matter (NAWM), and in areas with white matter hyperintensities (WMH). Error bars are standard deviations. All pairwise comparisons are statistically significant (p<0.001).

Figure 2

Voxels labeled as WMH in at least 5 subjects (in blue) superimposed on the mean CBF image derived by the average of all subjects' CASL images.

Figure 3

Mean group CBF displayed as a function of the frequency (i.e., number of subjects) in which voxels are labeled as WMH. Each circle represents a single voxel. For example, a single circle in Frequency = 5 represents the total group mean CBF for a voxel that is labeled as WMH in five subjects. Note subtle decline in group mean CBF across frequency (red dot) in marked decrease in variability, suggesting that areas with consistently lower CBF are most likely to be WMH across individuals. The number of voxels included for each frequency, 1 through 15, respectively, are 12109, 3811, 1796, 1125, 795, 608, 482, 377, 269, 212, 114, 58, 32, 10, and 4.