Diagnosing Alzheimer’s Disease

Alzheimer’s disease is a neurological disorder that causes memory loss, thinking and language problems, and behavior changes. It’s the most common type of dementia, a group of symptoms that, over time, cause a progressive reduction in a person’s ability to think, reason, and remember.

Many people as they age occasionally forget appointments or have a hard time finding the right words. But people with Alzheimer’s disease or another type of dementia have significant trouble with language, become increasingly confused or disoriented, find it difficult to make decisions, and experience changes in their behavior and personality.

Alzheimer’s disease is caused by structural changes in the brain. Abnormal deposits of proteins called tau tangles and beta-amyloid plaques begin to develop in a structure deep in the brain called the hippocampus—where sensory experience is processed so that it can be remembered—and in other areas of the brain used in thinking and decision making.

Plaques accumulate between the nerve cells, called neurons, which transmit information throughout the body, and tangles accumulate within the nerve cells. This buildup causes the neurons to work less efficiently, and, over time, lose their ability to communicate with each other. Eventually, the neurons die. It’s this brain cell death that leads to Alzheimer’s disease.

Risk Factors and Symptoms

Alzheimer’s disease isn’t part of the normal aging process, but the risk of developing it increases after age 65, and it’s estimated that about one-third of all people over age 85 have the disease. In early-onset Alzheimer’s disease, symptoms appear before age 65. Women are more likely than men to have the condition, partly because women live longer, on average.

Doctors don’t know exactly why the disease arises in certain people, but changes in the brain may start a decade or more before symptoms become apparent. Research suggests that factors including genetics, advanced age, a history of more than one head trauma, and lifestyle factors such as smoking may play a role in raising a person’s risk of Alzheimer’s disease.

The most common symptom of Alzheimer’s disease is short-term memory loss—a difficulty with remembering new information, such as recent conversations or the names of people. As the disease advances, other symptoms become more apparent: confusion and disorientation; mood and behavior changes; significant memory loss; and difficulty speaking, swallowing, sleeping, and walking. Eventually, people with Alzheimer’s disease can no longer care for themselves.

There are many possible causes of memory loss or confusion, including a condition called mild cognitive impairment; that’s why an accurate diagnosis is important. Some causes are reversible, such as vitamin deficiencies, medication side effects, or hypothyroidism, though others are permanent and progressive, such as Lewy body dementia. The earlier an Alzheimer’s disease diagnosis is made, the easier it is to manage symptoms and plan for care.

Diagnostic Tests

Doctors at NYU Langone provide expert evaluations for Alzheimer’s disease. To diagnose the disease, a specialist asks about symptoms, performs a physical exam, obtains thorough medical and family histories, and talks with family members or caregivers about how changes in mental status, mood, behavior, and memory are affecting a person’s daily life. He or she also uses additional diagnostic tools, including the following.

Neurological Evaluation

Doctors assess a person’s speech, vision and other senses, spatial skills, and reflexes. He or she may be asked to name objects, follow verbal and written commands, write a sentence, or draw a complex shape. Specialists may also ask him or her to walk a short distance, because gait problems can signal other conditions with Alzheimer’s-like symptoms, such as normal pressure hydrocephalus, an accumulation of fluid in the brain that leads to problems with walking, thinking, and controlling the bladder.

Cognitive Evaluation

Doctors also check cognitive skill—such as memory, ability to concentrate, and sense of time and place—by asking simple questions or talking with a family member or caregiver about how the person’s loss of these abilities affects everyday life. If a person has a type of dementia such as Alzheimer’s disease, he or she may have difficulty engaging in daily activities.

Psychiatric Evaluation

Because depression, anxiety, agitation, and hallucinations can be common features of Alzheimer’s disease, a doctor performs a psychiatric evaluation. A doctor may also ask questions about a person’s behavior and mood, as well as medication use, to assess if these could be contributing to symptoms.

Psychometric Testing

Psychometric tests measure the accuracy, speed, and quality of mental processes, such as making decisions, paying attention, using language, planning, organizing, remembering details, and problem solving. A person may be asked to take a pencil-and-paper neuropsychological exam to help the doctor determine whether dementia or something else has caused symptoms of cognitive impairment.

MRI Scan

MRI uses a magnetic field and radio waves to create two- or three-dimensional images of organs and tissues in the body. NYU Langone doctors may order this test to view the brain and rule out other causes of cognitive impairment, such as tumors or infections.

PET Scan

A PET scan uses a tracer, a small amount of a radioactive material combined with glucose (sugar), in creating a detailed image of the brain. The tracer is injected into a vein and travels through the body, collecting in the organs and tissues. This allows a doctor to see the blood flow to the brain, as well as how well the brain metabolizes sugar—an indication of how well it’s working over all. PET scan results can help a doctor to distinguish between Alzheimer’s disease and other forms of dementia.

Amyloid PET Imaging

Beta-amyloid plaques, abnormal clumps of protein in the brain, are one of the hallmarks of Alzheimer’s disease. With the help of a PET scan, doctors can detect beta-amyloid not only in plaques but also in the blood vessels supplying the brain. Amyloid imaging involves injecting a special radioactive tracer into a vein, where it enters the bloodstream and binds to the protein, which appears on a PET scan. This test can help doctors rule out other causes of dementia.

Because plaques are found in the brains of all people with Alzheimer’s disease, beta-amyloid likely plays an important role in the disease. But amyloid PET scan results do not confirm a diagnosis of Alzheimer’s—the presence of amyloid plaques only increases the likelihood that a person’s cognitive impairment is due to Alzheimer’s.

A doctor may use the results from this test, combined with other test results, to make a diagnosis and create a customized treatment plan. Our doctors help people and families understand the diagnosis and develop a care plan that may include medication, psychotherapy, or a clinical trial.