Diagnosis of Alzheimer's Disease

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. Such an examination will include a detailed medical history, physical (including laboratory examination) and neurological examination, neuropsychological testing and mental status test(s). Computerized Tomography (CT scan) or Positron Emission Tomography (PET scan), or magnetic resonance imaging (MRI), and electroencephalography (EEG) may also be indicated.

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. Related Disorders.

Other conditions have Alzheimer's-disease-like symptoms and need to be ruled out by a physician during the process of diagnosis. These include: * Multi-Infarct Dementia (MID) - a dementing disorder caused by multiple strokes (infarcts) * Parkinson's disease - a neurodegenerative disorder characterized by tremors, stiffness in the limbs and joints, speech impediment and, sometimes, dementia late in the course of the disease * Huntington's disease - an inherited, neurodegenerative disease whose symptoms include intellectual decline and irregular and involuntary movements of the facial muscles and limbs * Creutzfeldt-Jacob disease - a rare and fatal neurodegenerative disorder caused by an infectious transmissible organism that leads to rapid and pronounced mental deterioration * Pick's disease - a rare neurodegenerative disorder producing dementia involving the frontal and temporal cortex in which personality and behaviour are more notably affected earlier and more prominently than Alzheimer's disease.