Diagnosis of Alzheimer's Disease

An early, accurate diagnosis of AD helps persons with AD and their families plan for the future. It gives them time to discuss care options while the patient can still take part in making decisions. Early diagnosis also offers the best chance to treat the symptoms of the disease.

Today, the only definite way to diagnose AD is to find out whether there are plaques and tangles in brain tissue. To look at brain tissue, doctors must wait until they do an autopsy, which is an exam of the body done after a person dies. Therefore, doctors must make a diagnosis of "possible" or "probable" AD. Finding new and better ways to diagnose early AD is one area of current research.

At specialized centers, doctors can diagnose AD correctly up to 90 percent of the time. Doctors use several tools to diagnose probable AD:

• A complete medical history that includes information about the person's general health, past medical problems, and any difficulties the person has carrying out daily activities. The doctor may want to speak with the person's family and friends to get more information.

• Tests of blood, urine, or spinal fluid to look for other possible causes of the symptoms.

• Tests of memory, problem solving, attention, counting, and language.

• Brain scans that allow the doctor to look at a picture of the brain to see if anything does not look normal. Types of brain scans include computerized tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) scans.

Information from the medical history and from test results helps the doctor rule out other possible causes of the person's symptoms. For example, thyroid problems, drug reactions, depression, brain tumors, and blood vessel disease in the brain can cause AD-like symptoms. Some of these other conditions can be treated successfully.

Recently, scientists have focused on a type of memory change called mild cognitive impairment (MCI). MCI is different from both AD and normal age-related memory change. People with MCI have ongoing memory problems but do not have other losses like confusion, attention problems, and difficulty with language. Researchers are studying MCI to learn whether early diagnosis and treatment might prevent or slow further memory loss, including the development of AD.