ABSTRACT
The critical step in the diagnosis of Alzheimer disease (AD) is neuropathologic examination of biopsy or autopsy material. The results of the neuropathologic examination determine if the lesions are consonant with a diagnosis of AD. This chapter presents an overview, for the non-neuropathologist, of the terminology used to describe lesions seen in AD, to point out deficiencies in our understanding of these lesions, and to present results of recent research into the possible etiology of these lesions. Neurofibrillary tangles (NFT) are classically identified by histologic staining with silver. In addition to silver stains, NFT are also stained by thioflavin or Congo red, both of which are dyes that bind to protein in a B-pleated sheet conformation. Neuronal loss in AD tends to be the scientific step-sister to the more obvious pathology of senile plaques and NFT. This probably reflects the difficulties of quantifying shrinkage and neuronal loss; relatively few researchers have been willing to undertake this difficult task.
