Alzheimer's disease is distinguished from other forms of dementia by characteristic changes in the brain that are visible only upon microscopic examination during autopsy. Brains affected by Alzheimer's disease must show the presence of the following:
- Fiber tangles within nerve cells (neurofibrillary tangles)
- Clusters of degenerating nerve endings (neuritic plaques)
Another characteristic of Alzheimer's disease is the reduced production of certain brain chemicals necessary for communication between nerve cells, especially acetylcholine, as well as norepinephrine, serotonin, and somatostatin.