Amyloid and senile plaques and cerebral blood vessels. A semi-quantitative investigation of a possible relationship.

The possibility of a direct association between the amyloid in senile plaques and in cerebral blood vessels was tested by a quantitative analysis of amyloid in these sites in the autopsy brains of 15 patients suffering from senile dementia of Alzheimer type and 30 non-demented old subjects. The numbers and severity of involvement of vessels showing amyloid were expressed as a vascular 'amyloid score'. Over all the cases amyloid within vessels was found to increase with each decade but no direct correlation existed between age and amyloid scores. Plaques were found in the absence of vascular amyloid and in 2 cases, vascular amyloid occurred without plaque formation. Nevertheless, there was a statistically significant association between the presence of vascular amyloid and of plaques and a significant correlation between total amyloid scores and plaque counts in the temporal lobe of demented subjects. However, amyloid scores only explained about 30% of the variance in plaque counts and amyloid in vessels is unlikely to contribute to the development of all senile plaques. There was no significant correlation between the amount of vascular amyloid observed and the clinical severity of the dementia.