The Other Kinds: Dementia

Not every case of dementia--broadly defined as a progressive or permanent decline in intellectual function--is caused by Alzheimer's disease. In fact, there are dozens of conditions that can cause or mimic dementia, including depression, drug overdose, dehydration, anemia, syphilis, viral infections and vitamin deficiencies. Many of these are reversible if they are treated promptly, so it's important to get the proper diagnosis when you or someone you love starts experiencing serious mental deterioration.

Diagnosis can be tricky. Psychological tests go only so far because patients showing signs of dementia are often uncommunicative; failure to remember or fully answer questions can be as easily caused by severe depression as by full-fledged dementia. Doctors typically conduct a battery of tests, which can include blood counts, chest X rays and tests of thyroid function. Later this year the American Academy of Neurology will issue a new set of guidelines that emphasizes the importance of taking cat scans or magnetic resonance images of the brain. These are particularly good at revealing structural problems caused by ministrokes, blood clots, tumors and fluid buildup.

Treatment, of course, will depend on what the doctor finds. Some dementias are as irreversible as Alzheimer's or respond to different drugs. But you won't know what to expect or what treatment will be used until you know what you're dealing with.

--By Christine Gorman