Alzheimer disease is the most common form of dementia. It is a brain disease caused due to tau protein misfolding. This disease is incurable. This is degenerative disease. It can be diagnosed through MRI scan or PET. This disease is found in generally above 65 years of age. Its symptoms include irritation, confusion, mood swings and aggression. This disease is named after German psychiatrist and neuropathologist Alois Alzheimer in 1906.