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Tests and diagnosis
By Mayo Clinic staffDoctors can accurately diagnose 90 percent of Alzheimer's cases. Alzheimer's disease can be diagnosed with complete accuracy only after death, when microscopic examination of the brain reveals plaques and tangles.
To help distinguish Alzheimer's disease from other causes of memory loss, doctors typically rely on the following types of tests.
Lab tests
Blood tests may be done to help doctors rule out other potential causes of the dementia, such as thyroid disorders or vitamin deficiencies.
Neuropsychological testing
Sometimes doctors undertake a more extensive assessment of thinking and memory skills. This type of testing, which can take several hours to complete, is especially helpful in trying to detect Alzheimer's and other dementias at an early stage.
Brain scans
By looking at images of the brain, doctors may be able to pinpoint any visible abnormalities — such as clots, bleeding or tumors — that may be causing signs and symptoms. Positron emission tomography (PET) can reveal areas of the brain that may be less active and the density of amyloid plaques.
- Magnetic resonance imaging (MRI). An MRI machine uses radio waves and a strong magnetic field to produce detailed images of your brain. You lie on a narrow table that slides into the tube-shaped MRI machine, which makes loud banging noises during scans. The entire procedure can take an hour or more. MRIs are painless, but some people feel claustrophobic in the machine.
- Computerized tomography (CT). For a CT scan, you lie on a narrow table that slides into a small chamber. X-rays pass through your body from various angles, and a computer uses this information to create cross-sectional images, or slices, of your brain. The test is painless and takes about 20 minutes.
- Positron emission tomography (PET). During a PET scan, you'll be injected with a low-level radioactive material, which binds to chemicals that travel to the brain. You lie on a table while an overhead scanner tracks the radioactive material. This helps show which parts of your brain aren't functioning properly. The test is painless and can be particularly useful in distinguishing between different types of dementia.
- Alzheimer's disease fact sheet. National Institute on Aging. http://www.nia.nih.gov/Alzheimers/Publications/adfact.htm. Accessed Oct. 31, 2008.
- Shadlen MF, et al. Evaluation of cognitive impairment and dementia. http://www.uptodate.com/home/index.html. Accessed Nov. 3, 2008.
- Caselli RJ, et al. The degenerative dementias: Alzheimer's disease. In: Goetz CG, et al. Textbook of Clinical Neurology. 3rd ed. Philadelphia, Pa.: Saunders Elsevier; 2007. http://www.mdconsult.com/das/book/body/109112945-3/0/1488/287.html. Accessed Nov. 3, 2008.
- Alzheimer's information: Causes. National Institute on Aging. http://www.nia.nih.gov/Alzheimers/AlzheimersInformation/Causes/. Accessed Nov. 6, 2008.
- Shadlen MF, et al. Dementia syndromes. http://www.uptodate.com/home/index.html. Accessed Nov. 6, 2008.
- Basics of Alzheimer's disease: What it is and what you can do. Alzheimer's Association. http://www.alz.org/national/documents/brochure_basicsofalz_low.pdf. Accessed Nov. 6, 2008.
- Alzheimer's disease genetics fact sheet. National Institute on Aging. http://www.nia.nih.gov/Alzheimers/Publications/geneticsfs.htm. Accessed Nov. 6, 2008.
- Shadlen MF, et al. Risk factors for dementia. http://www.uptodate.com/home/index.html. Accessed Nov. 6, 2008.
- Kelley BJ, et al. Alzheimer's disease and mild cognitive impairment. Neurological Clinics. 2007;25:577.
- Late-stage care. Alzheimer's Association. http://www.alz.org/national/documents/brochure_latestage.pdf. Accessed Nov. 7, 2008.
- Dementia care practice recommendations for assisted living residences and nursing homes. Alzheimer's Association. http://www.alz.org/national/documents/brochure_DCPRphases1n2.pdf. Accessed Nov. 7, 2008.
- Neurological diagnostic tests and procedures. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/misc/diagnostic_tests.htm. Accessed Nov. 7, 2008.
- Press D, et al. Cholinesterase inhibitors in the treatment of dementia. http://www.uptodate.com/home/index.html. Accessed Nov. 7, 2008.
- Press D, et al. Treatment of dementia. http://www.uptodate.com/home/index.html. Accessed Nov. 7, 2008.
- Press D, et al. Prevention of dementia. http://www.uptodate.com/home/index.html. Accessed Nov. 7, 2008.
- Natural medicines in the clinical management of Alzheimer's disease. Natural Medicines Comprehensive Database. http://www.naturaldatabase.com. Accessed Nov. 10, 2008.
- Alexander M, et al. Patient information: Alzheimer's disease. http://www.uptodate.com/patients/content/topic.do?topicKey=~eWpcYl7lC9LRwe. Accessed Nov. 10, 2008.
- Press D, et al. Future directions in dementia treatments. http://www.uptodate.com/home/index.html. Accessed Nov. 7, 2008.
- Smith GE (expert opinion). Mayo Clinic, Rochester, Minn. Nov. 19, 2008.
- DeKosky ST, et al. Ginkgo biloba for prevention of dementia: A randomized controlled trial. Journal of the American Medical Association. 2008;19:2253.
