Amyloid plaques in cerebellar cortex and the integrity of Purkinje cell dendrites.

We probed serial and near serial sections of cerebellum from 13 Alzheimer's disease (AD), 10 older Down's syndrome (DS) patients, and 9 age-matched, non-AD controls, using single and double labeling immunohistochemistry to investigate the pathologic consequences of beta-amyloid or A4 (A beta) deposits in cerebellum and their relationship to Purkinje cells (PCs). Our data showed that A beta deposits in cerebellum of AD and older DS adults only form diffuse or preamyloid plaques and the density of A beta lesions per unit area of molecular layer correlated with the number of PCs per unit length of the subjacent PC layer in double immunostained sections (r = 0.85; p < 0.001). About 65% of these cerebellar A beta deposits were in physical contact with PC dendrites. No A beta plaques were found in the cerebellum of controls. Despite the abundance of A beta deposits in the cerebellar cortex of AD and older DS patients, neither PC bodies nor PC dendrites in physical contact with A beta lesions showed evidence of structural abnormalities.