There is no simple diagnostic test for Alzheimer's disease. Rather, a diagnosis of probable Alzheimer's disease is typically made by excluding other likely causes of dementia. When symptoms are noticed, a complete physical, psychiatric and neurologic evaluation should be performed by a physician experienced in the area of dementia. After a thorough examination is completed, a diagnosis of probable Alzheimer's disease can be made accurately in up to 90 percent of patients. Only a histopathologic examination of brain tissue, which is often done at autopsy to check for the presence of tangles and plaques, will confirm a diagnosis of Alzheimer's disease.
Neurofibrillary tangles are bundles of twisted fibers that accumulate in the cell bodies of neurons.
Neuritic plaques are round or oval lesions consisting of an amyloid protein core surrounded by fragments of damaged neurons. These types of lesions occur in the cerebral cortex and hippocampus, the regions of the brain which govern such higher intellectual functions as memory, thinking, reasoning and sensory perception. Cause The cause or causes of Alzheimer's disease are unknown. However, scientific research has begun to point in several directions. Neurotransmitter deficits have been implicated, with a deficiency of the neurotransmitter acetylcholine being a prominent and consistently identified deficit.