An electron microscopic study of cerebral biopsy specimens from 3 cases of Alzheimer's presenile dementia has revealed several points of interest. The two major findings have to do with the neurofibrillary tangles and senile plaques which are the characteristic features of this disease. It will be shown that the former are made up of large clusters of fine neurofibrils, while plaques have as their fundamental substance a different sort of filamentous material which is structurally identical to amyloid. Also noteworthy are certain myelin distortions suggestive of primary demyelinization; and a striking, although rare, endothelial change by which lipid-like material passes through the walls of small vessels to enter the lumen.
Cerebral biopsy specimens from 3 patients with Alzheimer's presenile dementia were examined by electron microscopy. Four major morphologic features were studied in detail: senile plaque, neurofibrillary tangle, myelin degeneration and endothelial modification.
The plaques had a core of amyloid fibrils. Large dendrites and axons with an excess of neurofilaments surrounded the core. Also prominent were neuronal processes which contained many laminated dense bodies. Microglia were present and seemed to be the source of the amyloid.
Alzheimer's neurofibrillary tangles were made up of great numbers of closely packed, normal neurofilaments which displaced the other cytoplasmic organelles within affected neuronal perikarya.
Myelin degeneration was often found without axonal degeneration. Wallerian degeneration was also noted.
Certain small vessels displayed endothelial fenestrations in which were several chylomicron-like vesicles. Dense particulate aggregates, possibly lipoprotein in nature, were seen to protrude from the endothelium into the lumen.