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Objective: Magnetic resonance (MR) imaging is used widely for assessment of patients with cognitive impairment, but the pathological correlates are unclear, especially when multiple pathologies are present., Methods: This report includes 93 subjects from a longitudinally followed cohort recruited for the study of Alzheimer's disease (AD) and subcortical cerebrovascular disease (CVD). MR images were analyzed to quantify cortical gray matter volume, hippocampal volume, white matter hyperintensities, and lacunes. Neuropathological examination quantified CVD parenchymal pathology, AD pathology (defined as Consortium to Establish a Registry for Alzheimer's Disease scores and Braak and Braak stage), and hippocampal sclerosis. Subjects were pathologically classified as 12 healthy control subjects, 46 AD, 14 CVD, 9 mixed AD/CVD, and 12 cognitively impaired patients without significant AD/CVD pathology. Multivariate models tested associations between magnetic resonance and pathological findings across the entire sample., Results: Pathological correlates of cortical gray matter volume were AD, subcortical vascular pathology, and arteriosclerosis. Hippocampal volume was related to AD pathology and hippocampal sclerosis, and the effects of hippocampal sclerosis were greater for subjects with low levels of AD pathology. White matter hyperintensities were related to age and to white matter pathology. Number of MRI lacunes was related to subcortical vascular pathology., Interpretation: In this clinical setting, the presence of lacunes and white matter changes provide a good signal for vascular disease. The neuropathological basis of MR defined cerebral cortical and hippocampal atrophy in aging and dementia is complex, with several pathological processes converging on similar brain structures that mediate cognitive decline.

Objective: To assess the interactions among three types of pathology (ie, cerebrovascular disease, hippocampal sclerosis [HS], and Alzheimer's disease [AD]), cognitive status, and apolipoprotein E genotype., Methods: We report clinicopathological correlations from 79 autopsy cases derived from a prospective longitudinal study of subcortical ischemic vascular disease and AD., Results: Thirty percent of the cases had significant cerebrovascular parenchymal pathology scores (CVDPS), 54% had significant AD pathology, and 18% had HS. In an ordinal logistic regression analysis that included interaction terms to assess the effects of each pathological variable when the other variables are interpolated to zero, each of the three pathology variables contributed independently to cognitive status: Braak and Braak stage odds ratio (OR) = 2.84 (95% confidence interval, 1.81-4.45), HS score OR = 2.43 (95% confidence interval, 1.01-5.85), and CVDPS OR = 1.02 (95% confidence interval, 1.00-1.04). Only Braak and Braak stage contributed to a global neuropsychological measure of cognitive impairment. Apolipoprotein E4 genotype was associated with Braak and Braak stage (OR, 1.31 [95% confidence interval, 1.03-1.68]), but not CVDPS or HS scores., Interpretation: In this convenience sample enriched for subcortical ischemic vascular disease, HS was a common unsuspected neuropathological finding. Apolipoprotein E4 genotype was associated with cerebral amyloid angiopathy, but not HS or arteriosclerosis. When Braak and Braak stage was interpolated to zero, both CVDPS and HS contributed to cognitive impairment. However, advancing stages of AD pathology overwhelmed the effects of CVDPS and HS, to become the major determinant of dementia.

The cornu ammonis 1 region of the hippocampus (CA1) sector of hippocampus is vulnerable to both Alzheimer's disease (AD)-type neurofibrillary degeneration and anoxia-ischemia. The objective of this article is to compare number and size of neurons in CA1 in AD versus ischemic vascular dementia. Unbiased stereological methods were used to estimate the number and volume of neurons in 28 autopsy-derived brain samples. For each case, the entire hippocampus from one cerebral hemisphere was sliced into 5mm slabs (5-7 slabs/case), cut into 50 microm sections, and stained with gallocyanine. Using the optical dissector, we systematically sampled the number and size of neurons throughout the extent of CA1 and CA2. The total number of neurons was significantly less in AD compared with ischemic vascular dementia (p < 0.02), but there was no significant difference in neuron size. The greatest loss of neurons was observed in two cases with combined AD and hippocampal sclerosis. Regardless of causative diagnosis, the number of CA1 neurons correlates with magnetic resonance imaging-derived hippocampal volume (r = 0.72; p < 0.001) and memory score (r = 0.62; p < 0.01). We conclude that although CA1 neuron loss is more consistently observed in AD than ischemic vascular dementia, severity of loss shows the expected correlation with structure and function across causative subtype. Reductions in magnetic resonance imaging-derived hippocampal volume reflect loss, rather than shrinkage, of CA1 neurons.