Alzheimer's Disease

Diagnosis

Alzheimer's disease is only one of several dementias that affect older adults. Your doctor will have to make an accurate diagnosis to rule out other potentially treatable illnesses that may be causing your symptoms. Other diseases that can cause Alzheimer's-like symptoms include dementia due to clogged arteries in the brain (vascular dementia), a buildup of fluid within the brain, normal-pressure hydrocephalus, and dementia associated with Huntington's disease, HIV infection, Parkinson's disease, or syphilis. In addition, certain vitamin deficiencies (e.g., B12), certain hormonal disorders (thyroid and pituitary, for example), and side effects of drugs can cause symptoms similar to those of Alzheimer's disease.

During the initial evaluation, the doctor will complete a careful medical history. Because a patient is often already experiencing memory loss by the time he or she goes to see a doctor, the help of a spouse or other family member is usually required. The doctor will ask questions about specific memory, cognitive, or behavioral problems the patient is experiencing, and the time at which they developed. The answers to these questions not only help to diagnose and stage the problem, but also provide a baseline for comparison of subsequent disease progression. The medical history will also include a series of questions intended to rule out other potentially treatable causes of the symptoms.

The initial evaluation will include mental status testing. Mental status testing is done by asking the patient questions, or by using standardized tests that measure various aspects of memory and cognition. The Mini Mental Status Examination, Blessed Dementia Scale, and 7-Minute Screen are some common examples. These tests, however, need to be interpreted by clinicians who can take into account factors such as education and baseline ability prior to the development of symptoms. For example, a mathematics professor should not be considered “normal” just because he can still balance his checkbook.

Your doctor will perform a physical examination and order laboratory tests to determine whether any co-existing or alternate causes of the dementia are present. A physical examination may identify signs of vascular disease, liver or kidney disease, drug toxicity, or vitamin deficiencies. The examination may also identify co-existing conditions—such as difficulty hearing or seeing—that could exacerbate the patient's condition. Typical tests include blood counts, blood chemistry, thyroid tests, and tests to identify systemic infections. The doctor will also order computed tomography (CT) or magnetic resonance imaging (MRI) of the head to identify strokes, brain tumors, or the build-up of fluid within or around the brain.

Alzheimer's disease is diagnosed when other potential causes of progressive memory loss and cognitive impairment have been ruled out. A definitive diagnosis of Alzheimer's disease can only be made after death, when the characteristic plaques and tangles of Alzheimer's disease are identified during an autopsy of the brain. Few people actually undergo an autopsy. For a diagnosis of probable Alzheimer's disease, the National Institute of Neurological and Communicative Disorders and Stroke/Alzheimer's Disease and Related Disorders Association uses the following definition: established dementia, deficits in two or more types of thought processes (for example, memory), progressive worsening of memory and other thought processes, no disturbance in consciousness, onset between 40 and 90 years of age, and absence of other brain diseases that could account for the symptoms.

Prevention and Screening

Currently, Alzheimer's disease cannot be prevented, though scientists are researching possible methods to prevent it. Genetic testing can identify people with an increased risk of developing the disease, but without a cure or treatment that can stop the disease from progressing, such knowledge has limited value.