How Alzheimer's is diagnosed

Alzheimer's disease can only officially be confirmed with clinical findings. A microscopic examination of brain tissue can reveal the presence of this disease.This is obtained from cerebral biopsy or an autopsy (if the person is deceased). 


image: http://www.123rf.com/photo_15688227_alzheimer-disease-brain-tissue-with-amyloid-plaque.html

However, typically brain scans are the preferred method if doctors are suspicious as this a much less invasive way of diagnosing AD. By comparing the brain activity of an Alzheimer's brain to a normal brain, the presence of AD can readily be observed. This picture shows the clear difference between a normal brain and one with AD.


Image: http://www.berkeley.edu/news/media/releases/2009/07/14_alzheimers.shtml

To put the degenerative effects of Alzheimer's disease into perspective here is a comparison of a normal brain vs one affected by Alzheimer's. You can see how much the brain shrunk because neural tissue died.

Image: http://blogs.atribuna.com.br/maissaude/wp-content/uploads/2015/08/alzheimer.jpg

Source: Porth, C., & Porth, C. (2007). Essentials of Pathophysiology: Concepts of Altered Health States (2nd ed.). Philadelphia: Lippincott Williams & Wilkins