[Alzheimer's disease. Histopathological and ultrastructural study of 6 cases (author's transl)]

Histologically Alzheimer's disease is chiefly characterized by senile plaques and neurofibrillary degenerations. Electron microscopy has clarified the basic morphological changes and has shed some light on the pathogenesis of the lesions. The senile plaque includes three components: neurites in various stages of degeneration, amyloid, and glial cells or processes. Degeneration of neurites is considered to represent the major change since it occurs before amyloid deposition, therefore playing a primary role in the development of the plaque: therefore the senile or neuritic plaque is the result of a neuronal disease, even though there is no evidence of perikarion injury. Neurofibrillary tangles are due to the accumulation in the neuronal cytoplasm of large clusters of abnormal neurotubules about 200 A diameter with periodic narrowings every 800 A (Twisted tubules). The nature and significance of the pathological material observed within the neurons are discussed.