What Dr. Alzheimer found in Auguste's brain were small clumps of hard proteins and tangled fibers called beta-amyloid peptides and tau tangles, respectively, the ends of nerve cells. The peptides accumulate on the outside of nerve cells in the brain and disrupt the flow of electrical signals between neurons, while the fibers choke the neurons until they die. This is why Alzheimer's disease progresses slowly, unlike a brain injury such as a stroke which destroys brain tissue immediately. The diagnosis of Alzheimer's can only be confirmed by an autopsy under a microscope, just like the discovery of the diseases by Dr. Alzheimer's. However, with current technology and differential diagnosis by a doctor, they can determine with certainty whether dementia is due to Alzheimer's disease. The doctor will order a battery of tests and take a medical history to rule out other possible preventable and reversible causes of dementia, such as alcohol overuse, drug interactions, or thyroid.