The impact of magnetic resonance imaging-detected white matter hyperintensities on longitudinal changes in regional cerebral blood flow

White matter hyperintensities are frequently detected on cranial magnetic resonance imaging (MRI) scans of older adults. Given the presumed ischemic contribution to the etiology of these lesions and the posited import of resting brain activity on cognitive function, we hypothesized that longitudinal changes in MRI-detected white matter disease, and its severity at a given time point, would be associated with changes in regional cerebral blood flow (rCBF) over time. We evaluated MRI scans and resting H₂¹⁵O positron emission tomographic rCBF at baseline and after an average of 7.7-year follow-up in Baltimore Longitudinal Study of Aging participants without dementia. Differences in patterns of rCBF were evident at baseline and at follow-up between the group of subjects showing increased white matter disease over the 8-year interval compared with the group with stable white matter ratings. Furthermore, longitudinal changes over time in rCBF also differed between the two groups. Specifically, the group with progressive white matter abnormalities showed greater increase in the right inferior temporal gyrus/fusiform gyrus, right anterior cingulate, and the rostral aspect of the left superior temporal gyrus. Regions of greater longitudinal decrease in this group were evident in the right inferior parietal lobule and at the right occipital pole. Changes in white matter disease over time and its severity at any given time are associated significantly with both cross-sectional and longitudinal patterns of rCBF. The longitudinal increases may reflect cortical compensation mechanisms for reduced efficacy of interregional neural communications that result from white matter deterioration.