ABSTRACT
Lesions observed in the brain of Alzheimer’s disease (AD) patients may be considered under three main headings: 1) extracellular Aβ deposition, 2) intracellular tau accumulation (that is, neurofibrillary pathology), and 3) loss of synapses and neurons. Aβ deposits include a) diffuse deposits that are devoid of neuritic components, and b) focal ones, which are sometimes amyloid; that is, they are stained by Congo red. The neuritic plaque is a composite lesion, with its core made of a focal Aβ deposit and its crown composed of processes, some of which are filled with tau protein. These processes are mainly axons.1 Microglial reaction is observed in close contact with the amyloid core2 and is related to a low-grade inflammation.3
