Alzheimer's disease: amyloid plaques in the cerebellum.

Two specific silver-staining methods demonstrating either extracellular amyloid and/or precursors of amyloid or intraneuronal neurofibrillary changes were used to examine cerebellar pathology in cases of presenile and senile dementia of the Alzheimer type, cases of Down's syndrome, and non-demented controls. The sensitivity of the techniques permitted visualization of large numbers of amyloid deposits in the cerebellar cortex of demented individuals. Similarly large numbers of amyloid deposits were not found in the cerebella of non-demented individuals. Neurofibrillary changes were absent. The majority of amyloid plaques occurred in the molecular layer. Quite a number of these displayed large diameters extending from the upper surface down to the Purkinje cell layer. Within the granular layer and white matter the plaques were less frequently encountered and they were less voluminous than those of the molecular layer. The cerebellar amyloid plaques were morphologically different and could easily be distinguished from the cerebellar plaques found in transmissible spongiform encephalopathies.