<unk>  beta immunostaining showing<unk>  (brown).<unk>  (also known as neuritic<unk> , Aβ<unk>  or senile<unk>  are extracellular deposits of the<unk>  beta (Aβ) protein mainly in the grey matter of the brain. Degenerative neuronal elements and an abundance of microglia and astrocytes can be associated with<unk> . Some<unk>  occur in the brain as a result of senescence (aging), but large numbers of<unk>  and neurofibrillary tangles are characteristic features of Alzheimer's disease. Abnormal neurites in<unk>  are tortuous, often swollen axons and dendrites. The neurites contain a variety of organelles and cellular debris, and many of them include characteristic paired helical filaments, the ultrastructural component of neurofibrillary tangles. The<unk>  are highly variable in shape and size; in tissue sections immunostained for Aβ, they comprise a log-normal size distribution curve with an average<unk> area of 400-450 square micrometers (µm²). The smallest<unk>  (less than 200 µm²), which often consist of diffuse deposits of Aβ, are particularly numerous. The<unk> parent size of<unk>  is influenced by the type of stain used to detect them, and by the plane through which they are sectioned for analysis under the microscope.<unk>  form when Aβ misfolds and aggregates into oligomers and longer polymers, the latter of which are characteristic of<unk> . Misfolded and aggregated Aβ is thought to be neurotoxic, especially in its oligomeric state.
Amyloid plaques
Neurofibrillary tangle
Geographic atrophy
Microinfarct
Superficial siderosis
Ballooning degeneration
Hippocampal sclerosis
Angioid streaks