Diagnosing Alzheimer's disease

No blood test, brain scan, or physical exam can definitively diagnose Alzheimer's disease. And because so many conditions can produce symptoms resembling those of early Alzheimer's, reaching the correct diagnosis is complicated.

Finding a physician

It's important to find a physician experienced in Alzheimer's diagnosis. If a physician diagnoses Alzheimer's after only a cursory examination, get a second opinion. A complete evaluation by a physician experienced in diagnosing Alzheimer's is essential to exclude other health problems that could cause cognitive difficulties. Your family physician may do part of the evaluation and then recommend a neurologist, geriatrician, or other specialist to complete it. Your local Alzheimer's Association chapter, medical school, or hospital can also help identify appropriate specialists.

Before scheduling an appointment, ask what diagnostic procedures will be used. If the evaluation does not sound comprehensive (see "The evaluation process"), seek another physician. If you are unsatisfied with the evaluation, get a second opinion.

Once a diagnosis is made, find a physician experienced in providing ongoing care to meet the changing needs of someone with Alzheimer's disease. The doctor who makes the diagnosis may not be the one who will oversee the long-term care. For this purpose, the family needs to choose someone who's knowledgeable about managing dementing illnesses and able to communicate well with family members.

What to expect

A complete evaluation will take more than a day and is generally done on an outpatient basis. In most areas, the evaluation can be done locally, and tests can be spread over several days to avoid tiring the person being examined. Other specialists besides the treating physician may be involved in the evaluation, including technicians, nurses, psychologists, occupational or physical therapists, social workers, and often psychiatrists.

It will take several days before test results are reported and the physician reviews them. When the doctor discusses the findings, be prepared for an equivocal diagnosis. Physicians are often hesitant to diagnose Alzheimer's disease without first observing that the dementia is progressive. This means repeating the evaluation, usually in 6–12 months. At this later time, a much more confident diagnosis is sometimes possible, but when cognitive changes are gradual, the doctor may recommend repeated testing at yearly intervals.

The evaluation process

To help alleviate any stress associated with your visit to the physician, it's best to be as prepared as possible. For instance, be sure that whoever goes with the individual being evaluated is familiar with his or her medical history, current symptoms, and concerns. It's always helpful to write down in advance any issues you want to mention at the visit. Particularly if the person is in an advanced stage of dementia, you may want to bring a cassette or CD player with headphones to play calming music, or a familiar soft item that can be stroked or held.

Personal medical history

The physician will need the following:

A detailed description of changes in mental abilities, personality, mood, and behavior, including when and how the changes began and how they have affected the individual's ability to function. Letters, checkbooks, household lists, or other materials that illustrate changes in cognition may also be helpful.

Information about physical complaints or symptoms, such as loss of coordination, sudden vision problems, or weakness

A complete medical history, including injuries and recent illnesses

A list of medications the patient is taking, including nonprescription drugs and herbal supplements

Information about the medical problems of family members, especially relatives with a similar illness.

This may seem like a lot of information, but the person's history provides the foundation for the doctor's diagnostic workup. It enables the physician to construct a list of possible diagnoses that will guide the medical evaluation that follows.

For example, a physician who usually schedules a computed tomography (CT) scan of the brain as a final test might order one immediately for someone with abrupt mental changes and difficulty walking. These symptoms might indicate excess cerebrospinal fluid around the brain, a condition called normal-pressure hydrocephalus (see "Brain scans"), and prompt detection and treatment could prevent permanent damage to the brain.

Physical examination

Disorders as diverse as heart failure, liver disease, kidney failure, thyroid disorders, and respiratory diseases can cause dementia-like changes. What's more, elderly people don't always have typical symptoms of an illness. The sensation of pain is often dulled in the older person, for example, and it's not unusual for confusion, rather than chest pain, to be the main symptom of a heart attack.

Therefore, the physician will evaluate the cardiovascular system, lungs, and other organs for any signs of abnormalities. Because sensory losses can add significantly to a person's cognitive difficulties, the doctor will also test the individual's vision and hearing. The physician will also pay close attention to the nervous system, because neurologic abnormalities may signal a brain disorder other than Alzheimer's disease.

Muscle tone and strength, coordination, reflexes, senses, eye movement, and the pupils' reaction to light can tell the physician about the health of specific areas of the brain. For example, unequal reflexes or weakness on one side of the body suggests localized brain damage (perhaps from stroke or tumor), while tremors or other involuntary movements may indicate a degenerative disorder such as Parkinson's disease. These types of abnormalities are not usually features of early Alzheimer's disease.

Mental status testing, which is part of the neurologic examination, is crucial in diagnosing dementia and delirium. The physician will ask the person to perform simple mental exercises such as counting backward by sevens, obeying written instructions, memorizing words, and copying designs. This testing of mental status allows the physician to assess orientation, memory, comprehension, language skills, and ability to perform simple calculations.

Refusing to see the doctor

Families sometimes encounter a major stumbling block when the person whose mental status has aroused concern refuses to see a doctor. Often the person denies having cognitive difficulties and resists visiting a doctor for evaluation. In this case, arranging a doctor's visit for a more general purpose, such as a physical exam, or for a specific complaint, such as a headache, might provide an opportunity to begin the Alzheimer's evaluation. Call the doctor in advance to inform him or her that this is one purpose for the visit.

Diagnostic tests

The physician will order a complete blood count and blood chemistry tests to detect anemia, infection, diabetes, and kidney and liver disorders. Other lab work will include routine tests for thyroid function, vitamin B₁₂ deficiency, and elevated blood calcium, as well as a test for syphilis. If the physician suspects a specific medical problem, he or she may order additional tests. For example, a patient who might have been exposed to the AIDS virus will be encouraged to have an HIV test.

Brain scans. A brain scan — either computed tomography (CT) or magnetic resonance imaging (MRI) — is generally included in the standard evaluation for Alzheimer's disease and other forms of dementia.

CT and MRI scans, which reveal the anatomic structure of the brain, are used to rule out such problems as tumor, hemorrhage, stroke, and hydrocephalus, which can masquerade as Alzheimer's disease. These scans can also show the loss of brain mass associated with Alzheimer's disease and other dementias. In Alzheimer's disease, the region of the brain known as the hippocampus may be disproportionately atrophied.

Other brain scans may be performed if CT and MRI scans are inconclusive. Positron emission tomography (PET) and single positron emission computed tomography provide images of brain activity based on blood flow, oxygen consumption, or glucose use. These techniques can help narrow down a diagnosis, but even they do not reveal the microscopic changes in brain tissue that characterize Alzheimer's disease and thus can't identify the disease with certainty.

But the diagnostic capability of brain scans is improving. Especially promising is a kind of PET scan that uses a chemical tracer called Pittsburgh Compound-B (PIB). This chemical binds specifically to amyloid deposits in the brain, allowing them to show up clearly on the brain scans. The scans were detailed enough to identify people with early Alzheimer's disease in a 2004 pilot study in Annals of Neurology . Experts expect PET scans with PIB to be in general use within the next few years. Researchers also hope to perfect MRI techniques that can enhance physicians' ability to measure brain atrophy and diagnose Alzheimer's with greater accuracy.

EEG. An electroencephalogram (EEG) may be done to detect abnormal brainwave activity. Although the EEG is usually normal in people with mild Alzheimer's disease and many other types of dementia, EEG abnormalities do occur in delirium and Creutzfeldt-Jakob disease, which is a cause of dementia. If hydrocephalus (excess cerebrospinal fluid in the area around the brain) or infection of the central nervous system is suspected, the doctor may recommend a lumbar puncture to detect increased pressure or inflammatory cells in the spinal fluid.

Neuropsychological testing. Psychologists or neuropsychologists (psychologists with specialized training in brain disorders) may administer comprehensive neuropsychological tests, either as interviews or as paper-and-pencil tests. These tests, which take several hours, are used to determine what areas of cognitive function are impaired and what areas are still intact. They assess memory, reasoning, writing, vision-motor coordination, comprehension, and the ability to express ideas. A doctor may also give other tests to identify depression and other emotional problems.

Functional assessment. Cognitive problems affect a person's daily functioning in many different and sometimes surprising ways. An objective assessment can help determine what a person can and cannot do. This information is invaluable for caregivers, especially when the individual has other health problems that complicate the situation, such as arthritis or poor vision. If the person seems to have Alzheimer's, a functional assessment can help determine its stage, which can help family members decide what type of care and support services are needed.

In functional assessment, the therapist asks a family member to fill out a questionnaire about the person's ability to perform activities of daily living. By noting what activities the person completes successfully, partially, or not at all, the therapist can suggest ways of helping the individual accomplish these tasks, thereby preserving as much of his or her independence as possible.

Psychosocial evaluation. The psychosocial evaluation is usually conducted by a social worker and is designed to help the individual's family plan for care. The social worker will discuss the emotional, physical, and financial impact of Alzheimer's disease and guide the family through an evaluation of their circumstances. Social workers can also help coordinate community services, suggest alternatives to the person's present living arrangements, and provide a list of resources and locally available services.

Specialized tests

The doctor may call for a blood test in cases where there's a family history of early-onset Alzheimer's. That's because, to date, genetic testing offers diagnostic value only in cases of early-onset familial Alzheimer's disease. Searching for genetic mutations in individuals who do not have a strong family history of Alzheimer's and who did not show symptoms before age 65 is fruitless. The test for the ApoE genotype (see "Late-onset Alzheimer's disease") can increase diagnostic confidence somewhat, but it isn't recommended for screening purposes.

Biochemical markers for Alzheimer's pathology — including amyloid plaques, neurofibrillary tangles, and neurodegeneration — can be detected in spinal fluid. Currently, lumbar puncture, which extracts spinal fluid, has a limited role in diagnosis, but it may become more widespread now that the diagnostic markers for Alzheimer's disease are becoming more specific.

Review Date: 2007-01-01

Harvard Medical School does not endorse products or services.