Chapter 11 - Relationship of plaques and tangles to Alzheimer's disease phenotype

Abstract

This chapter discusses relationship of plaques and tangles to Alzheimer's disease (AD) phenotype. The clinical features of AD are pleiomorphic and in the early stages overlap the changes associated with normal aging. The probability that dementia is caused by AD then is determined by the exclusion of other known causes of dementia and by the degree to which the clinical presentation and course are characteristic of known cases of AD. Executive functioning, or the ability to inhibit inappropriate responses and select key information and behaviors for action often is affected early in dementia of the Alzheimer's type (DAT), and results in poor judgments and problem solving. There is increasing support for the possibility that phenotypic variants of DAT reflect different aetiologies that share a final common pathway of cerebral degeneration that in turn produces the general clinical features of gradually progressive impairment of memory and other cognitive functions. It is found that correlations between neocortical tangle densities and clinical measures of dementia severity are greater than for neocortical plaques and dementia severity. The neuronal counts, synaptic densities, and vascular amyloid burden have also been analyzed for associations with clinical status in AD.