After death the examined brain of an Alzheimer victim shows two distinct characteristics. The first is the presence of neuritic plaques in the cerebral cortex and other areas of the brain including cerebral blood vessels. These plaques consist of groups of neurons surrounded by deposits of beta-amyloid protein. The presence of these plaques is also common to other types of dementia. The second characteristic, neurofibliary tangles, is what separates AD from all other forms of dementia.
Neurofibliary tangles take place within the disconnected brain cells themselves.
When examined under a microscope diseased cells appear to contain spaghetti-like tangles of normally straight nerve fibers. The presence of these tangles was first discovered in 1906 by the German neurologist Alois Alzheimer, hence the name Alzheimer's disease. Although the characteristics listed above are crucial to the diagnosis of AD upon death, the clinical diagnosis involves a different process. The diagnosis of AD is only made after all other illnesses, which may have the same symptoms, are ruled out. The initial symptoms of AD are typical of other treatable diseases therefore doctors are hesitant to give the diagnosis of Alzheimer's in order to save the patient from the worsening of a treatable disease through a misdiagnosis.