July 2, 2010
Dear Mayo Clinic:
I am 64 and recently had a brain scan that detected signs of early dementia. My family doctor told me it is probably something I will begin to experience in the next five to 10 years. How accurate is this?
Although a brain scan can help identify changes in brain structure, results from a brain scan alone can't be used to diagnose dementia. And, even the best diagnostic imaging tools available today cannot predict if you will eventually develop signs and symptoms of dementia years down the road. Your case seems to require more conversation with your doctor to determine exactly what the brain scan showed and what the results mean.
Dementia isn't a specific disease. Instead, it's a clinical diagnosis. The term dementia describes a group of symptoms — such as memory loss, impaired reasoning, inability to learn or remember new information, personality changes, or inappropriate behavior — that affect a person's intellectual and social abilities enough to cause difficulty in performing daily activities.
Diagnosing dementia typically involves reviewing an individual's medical history and conducting a physical exam. In addition, tests that measure cognitive function — attention, memory, language and spatial skills, among others — are usually part of a diagnostic assessment of dementia, along with a neurological evaluation. This is done to investigate the cause and extent of signs and symptoms that have already appeared in someone who is having difficulty with, for example, memory, thinking, reasoning or daily functioning.
Dementia has a variety of possible causes, including progressive disorders like Alzheimer's disease and Lewy body dementia, as well as reversible conditions, such as infections, immune disorders and nutritional deficiencies, among many others.
Because dementia is caused by conditions that affect the brain or alter brain structure, brain scans can be helpful in diagnosis. Brain scans allow your doctor to see changes in the brain such as brain shrinkage, as well as visible abnormalities such as blood clots, strokes or tumors, that can help identify the underlying cause of dementia. But even if you have changes within your brain, if you aren't experiencing any signs or symptoms of dementia, then those brain changes don't really tell us anything about whether you will eventually develop dementia.
Currently, magnetic resonance imaging (MRI) is the best tool we have to visualize brain structure. MRI is a technique that uses a magnetic field and radio waves to create detailed images of the organs and tissues in your body. Yet even these advanced scans are not helpful in predicting who will get dementia five or 10 years from now.
I cannot speculate on what your physician saw on your brain scan. It's possible that brain changes were evident, but conclusions regarding dementia cannot be drawn from a brain scan alone. I'd encourage you to follow up with your doctor to discuss the results of the brain scan in more detail and find out exactly what it showed and what the findings mean. Alternatively, you could obtain the results of the brain scan from your doctor and review them with a neurologist who could provide another perspective on your situation.
— David Knopman, M.D., Neurology, Mayo Clinic, Rochester, Minn.