Comparison of positron emission tomography, cognition, and brain volume in Alzheimer's disease with and without severe abnormalities of white matter.

Abstract

Objectives-To examine cerebral metabolism, cognitive performance, and brain volumes in healthy controls and two groups of patients with probable Alzheimer's disease, one group with severe abnormalities of white matter (DAT +) and the other group with none, or minimal abnormalities (DAT -). Methods-Neuropsychological tests, CT, MRI, quantitative MRI, and PET studies were carried out to allow comparison between the DAT + and DAT -groups and the healthy controls. Results-Compared with the healthy controls, both demented groups had significandy reduced global and regional cerebral metabolism, significant brain atrophy, and significantly lower scores on neuropsychological testing.The DAT -patient group showed a pattern of parietal-temporal cerebral metabolic reductions and neuropsychological performance deficits typical of Alzheimer's disease. In addition, metabolism in the association neocortex (AD ratio) and measures of neuropsychological task performance were significantly correlated in the DAT -patient group.Comparison of DAT + with DATpatients showed a significantly higher ratio of parietal to whole brain glucose utilisation for the DAT + group. Moreover, when comparing group z score differences from the healthy controls, the DAT + group had, on average, smaller differences from controls in the frontal, parietal, and temporal regions than did the DAT -group. Discriminant analysis using metabolic ratios of the frontal, parietal, and temporal regions showed cerebral metabolic patterns to be significantly different among the DAT +, the DAT-, and the healthy controls. These differences were due primarily to relatively higher frontal, parietal, and temporal metabolic ratios in the DAT + group which resulted in discriminant scores for the DAT well as no significant correlations between metabolism in the association neocortex and neuropsychological performance. These differences probably reflect the superimposed pathology of the abnormalities of white matter which may exert their affect through disruption of long corticocortical pathways.

Correlates of memory function in community-dwelling elderly: The importance of white matter hyperintensities

“…It is interesting that the bivariate association between DelRec and the log-transformed WMH variable is significant in normals since some previous studies have also found significant associations between cognition and WMH in healthy elderly (DeCarli et al, 1995;Swan et al, 1998Swan et al, , 2000 while some have not (DeCarli et al, 1996;Kozachuk et al, 1990;O'Brien et al, 1997). A more limited range of WMH in normals may have contributed to these conflicting findings (Gunning-Dixon & Raz, 2000).…”

“…A more limited range of WMH in normals may have contributed to these conflicting findings (Gunning-Dixon & Raz, 2000). However, the specific association between episodic memory and WMH is significant but rather weak in several studies (DeCarli et al, 1995;Libon et al, 1998;Ylikoski et al, 1993) and a recent meta-analysis (Gunning-Dixon & Raz, 2000) suggesting a weak association in the more commonly studied groups of AD patients and normals (DeCarli et al, 1996;Swan et al, 2000;Ylikoski et al, 1993).…”

Independent Cognitive Effects of Atrophy and Diffuse Subcortical and Thalamico-Cortical Cerebrovascular Disease in Dementia

“…3,4 Those with AD and WMHI show greater visuospatial dysfunction, 5 attention/concentration impairment, 6 slower cognitive processing, and greater executive dysfunction 6 than those with AD alone, but other studies find no neuropsychological differences between these 2 groups. [7][8][9] Functional imaging studies show different activation patterns in those with and without WMHI, suggesting that an equivalent level of cognitive impairment results from different mechanisms in AD with and without WMHI. 7,10 In contrast to subtle and often controversial cognitive correlates of CVD-related MRI hyperintensities, MRI measures of atrophy have shown stronger and more consistent relationships with cognitive impairment.…”

[18F]Fluorodeoxyglucose Positron Emission Tomography in Alzheimer Disease and Related Disorders

“…White matter hyperintensity on MR imaging and lacunar infarction may contribute to reduction in cerebral blood flow and glucose metabolism (DeCarli et al, 1996;Miyazawa et al, 1997). Several studies tried to identify distinctive patterns for vascular dementia on FDG-PET, but due to the limitations of the visual method on FDG-PET, no definitive finding could be obtained (De Reuck et al, 1998;Mielke et al, 1994;Sultzer et al, 1995).…”