White matter magnetic resonance hyperintensities in dementia of the Alzheimer type: Morphological and regional cerebral blood flow correlates

In a prospective MRI study the presence, appearance, volume, and regional cerebral blood flow (rCBF) correlates of periventricular hyperintensities (PVHs) and deep white matter hyperintensities (DWMI{s) were examined in 18 patients with probable Alzheimer's disease and in 10 age matched healthy control subjects, all without major cerebrovascular risk factors. The ¹³³Xe inhalation method and the [^99mTc]-d,l-hexamethyl-propy1ene- amine-oxime (HMPAO) technique with single photon emission computed tomography (SPECT) were used to measure rCBF. Rating scores for PVHs were significantly higher in the Aizheimer's disease group (p <0.01) and correlated significantly with the volume of ventricles (p < 0.05) and with systolic arterial blood pressure (p <0.01), but not with rCBF. By contrast, there was no significant difference in the rating scores or volumes of DWMUs between the two groups, although three patients had extensive DWMH lesions in the central white matter. In the group of patients with Aizheimer's disease as a whole, the volume of DWMBs correlated well with rCBF in the hippocampal region (r =-072; p <0.001), but not with frontal, temporal, parietal, or occipital rCBF. Postmortem histopathology of extensive DWMH lesions in one patient with definite Alzheimer's disease showed a partial loss of myelin and astrocytic gliosis, but no ischaemic changes. It is concluded that DWMII lesions may be associated with reduced rCBF in the hippocampal region. The heterogenous topography of neocortical rCBF deficits in Aizheimer's disease could not be explained by deafferentation from underlying white matter hyperintensities and therefore may reflect variations in the topography of cortical abnormalities.