Effect of white matter hyperintensities on cortical cerebral blood volume using perfusion MRI.

White matter hyperintensities (WMHs) are commonly seen on brain magnetic resonance imaging (MRI) scans of elderly individuals, but their functional significance remains controversial. We used perfusion-weighted MRI to determine the impact of WMHs on cortical regional cerebral blood volume (rCBV). We studied 24 elderly stroke patients and 27 control subjects with conventional MRI which included T2-weighted FLAIR coronal slices through whole brain and gadolinium-DTPA (0.2 mmol/kg)-based perfusion MRI (pMRI) with echo planar imaging. Volumes of WMHs, including deep WMHs and periventricular hyperintensities (PVHs), were computed by an automated method after excluding regions of infarction. Partial correlations between WMH and corresponding cortical rCBV were determined after correction for age and atrophy. The relative rCBV of gray matter was higher in control subjects and there was no significant hemispheric asymmetry. When both stroke and control groups were included, there were significant correlations among frontal cortical rCBV and frontal WMHs, temporal cortical rCBV with temporal WMHs, and cortical rCBV with both total deep WMHs and PVHs. Although the trends of correlation still existed when the two groups were analyzed separately, they were not significant. The correlations between cortical rCBV and WMHs in the same lobe were significant for subjects with more severe hyperintensities irrespective of the group. In conclusion, T2-weighted WMHs are associated with reduced rCBV in the cerebral cortex, particularly in individuals with extensive hyperintensities.