Structural correlates of cognitive deficits in a selected group of patients with Alzheimer's disease

Objective: The objective of this study was to correlate the densities of ne urofibrillary tangles (NFTs) and senile plaques (SPs) in 10 patients with A lzheimer's disease (AD) with comprehensive neuropsychological data obtained within 1 year of death. Background: Clinicopathologic studies in AD have b een essentially limited to correlate neuropathologic data with severity of dementia. Very few studies have addressed the correlations between distribu tion of lesions and specific cognitive deficits. This is partly due to the limitation imposed by the interval between the last neuropsychological eval uation and death. Methods: Ten patients with a postmortem diagnosis of AD, with a mean age at death of 80.4 +/- 6.6 years and a mean duration of sympt oms of 5.6 +/- 2.9 years, were selected for the study. All of these patient s were submitted to neuropsychological testing within 1 year of death, incl uding 17 tests assessing memory, language, visuoperceptual, visuospatial, a nd constructional abilities as well as limb praxis. The neuropathologic stu dy was performed using a modified Bielschowsky technique. Mean densities of SPs and NFTs were determined in the hippocampal formation (CA1, subiculum, and parasubiculum) and in six neocortical areas (midfrontal, orbitofrontal , cingulum, fusiform gyrus, superior and inferior parietal cortices). Stati stical correlations were determined between cognitive scores and SP and NFT densities. Results: For NFTs, significant correlations emerged only betwee n tangle density in CA1 and visuoperceptual scores. For SP density values, significant correlations were found between visuoperceptual tests and lesio ns in the subiculum and in the fusiform gyrus, significant correlations wer e found between language scores and SPs in the superior parietal cortex and between visuospatial deficits and lesions in the superior parietal cortex and fusiform gyrus. Conclusions: SPs in specific brain areas displayed a go od correlation with the cognitive deficits detected in this selected group of AD patients. The association of fusiform gyrus and superior parietal lob ule involvement with visuoperceptual and visuospatial deficits, respectivel y, is in agreement with current knowledge of the anatomic basis of visual p rocessing.