Diagnosing Alzheimer's: How Alzheimer's is diagnosed

To diagnose Alzheimer's dementia, doctors conduct tests to assess memory impairment and other thinking skills, judge functional abilities, and identify behavior changes. They also perform a series of tests to rule out other possible causes of impairment.

By Mayo Clinic Staff

To diagnose Alzheimer's dementia, doctors evaluate your signs and symptoms and conduct several tests.

An accurate diagnosis of Alzheimer's dementia is an important first step to ensure you have appropriate treatment, care, family education and plans for the future.

Early signs and symptoms of Alzheimer's dementia

Early signs and symptoms of Alzheimer's dementia include:

  • Memory impairment, such as difficulty remembering events
  • Difficulty concentrating, planning or problem-solving
  • Problems finishing daily tasks at home or at work
  • Confusion with location or passage of time
  • Having visual or space difficulties, such as not understanding distance in driving, getting lost or misplacing items
  • Language problems, such as word-finding problems or reduced vocabulary in speech or writing
  • Using poor judgment in decisions
  • Withdrawal from work events or social engagements
  • Changes in mood, such as depression or other behavior and personality changes

Alzheimer's dementia can affect several aspects of your daily life.

When warning signs of Alzheimer's dementia appear, it's important that you get a prompt and accurate diagnosis.

Diagnosing Alzheimer's dementia

To diagnose Alzheimer's dementia, your primary doctor, a doctor trained in brain conditions (neurologist) or a doctor trained to treat older adults (geriatrician) will review your medical history, medication history and your symptoms. Your doctor will also conduct several tests.

During your appointment, your doctor will evaluate:

  • Whether you have impaired memory or thinking (cognitive) skills
  • Whether you exhibit changes in personality or behaviors
  • The degree of your memory or thinking impairment or changes
  • How your thinking problems affect your ability to function in daily life
  • The cause of your symptoms

Doctors may order additional laboratory tests, brain-imaging tests or send you for memory testing. These tests can provide doctors with useful information for diagnosis, including ruling out other conditions that cause similar symptoms.

Ruling out other conditions

Doctors will perform a physical evaluation and check that you don't have other health conditions that could be causing or contributing to your symptoms, such as signs of past strokes, Parkinson's disease, depression or other medical conditions.

Assessing memory problems and other symptoms

To assess your symptoms, your doctor may ask you to answer questions or perform tasks associated with your cognitive skills, such as your memory, abstract thinking, problem-solving, language usage and related skills.

  • Mental status testing. Your doctor may conduct mental status tests to test your thinking (cognitive) and memory skills. Doctors use the scores on these tests to evaluate your degree of cognitive impairment.
  • Neuropsychological tests. You may be evaluated by a specialist trained in brain conditions and mental health conditions (neuropsychologist). The evaluation can include extensive tests to evaluate your memory and thinking (cognitive) skills.

    These tests help doctors determine if you have dementia, and if you're able to safely conduct daily tasks such as driving and managing your finances. They provide as much information on what you can still do as well as what you may have lost. These tests can also evaluate if depression may be causing your symptoms.

  • Interviews with friends and family. Doctors may ask your family member or friend questions about you and your behavior.

    Doctors look for details that don't fit with your former level of function. Your family member or friend often can explain how your thinking (cognitive) skills, functional abilities and behaviors have changed over time.

This series of clinical assessments, the physical exam and the setting (age and duration of progressive symptoms) often provide doctors with enough information to make a diagnosis of Alzheimer's dementia. However, when the diagnosis isn't clear, doctors may need to order additional tests.

Laboratory tests

You may have laboratory tests to rule out other disorders that cause some symptoms similar to those of Alzheimer's dementia, such as a thyroid disorder or vitamin B-12 deficiency.

Brain-imaging tests

Alzheimer's dementia results from the progressive loss (degeneration) of brain cells. This degeneration may show up in a variety of ways in brain scans.

However, these scans alone aren't enough to make a diagnosis. Scans aren't used to diagnose the condition because there is overlap in what doctors consider normal age-related change in the brain and abnormal change.

However, brain imaging can help:

  • Rule out other causes, such as hemorrhages, brain tumors or strokes
  • Distinguish between different types of degenerative brain disease
  • Establish a baseline about the degree of degeneration

The brain-imaging technologies most often used are:

  • Magnetic resonance imaging (MRI). An MRI uses powerful radio waves and magnets to create a detailed view of your brain.
  • Computerized tomography (CT). A CT scan uses X-rays to obtain cross-sectional images of your brain.
  • Positron emission tomography (PET). A PET scan uses a radioactive substance known as a tracer to detect substances in the body. There are different types of PET scans. The most commonly used PET scan is a fluorodeoxyglucose (FDG) PET scan, which can identify brain regions with decreased glucose metabolism. The pattern of metabolism change can distinguish between different types of degenerative brain disease.

    PET scans have recently been developed that detect clusters of amyloid proteins (plaques), which are associated with Alzheimer's dementia, but this type of PET scan is typically used in the research setting.

Future of diagnosis

Researchers are working on new diagnostic tools that may enable doctors to diagnose Alzheimer's dementia earlier in the course of the disease, when symptoms are very mild or before symptoms even appear. One such tool is a PET scan that can detect tau, the other hallmark abnormal protein in Alzheimer's dementia.

Scientists are investigating a number of disease markers and diagnostic tests, such as genes, disease-related proteins and imaging procedures, which may accurately and reliably indicate whether you have Alzheimer's dementia and how much the disease has progressed. However, more research on these tests is necessary.

Benefit of an early diagnosis

Reluctance to go to the doctor when you or a family member has memory problems is understandable. Some people hide their symptoms, or family members cover for them. That's easy to understand, because Alzheimer's dementia is associated with loss, such as loss of independence, loss of a driving privileges and loss of self. Many people may wonder if there's any point in a diagnosis if there's no cure for the disease.

It's true that if you have Alzheimer's dementia or a related disease, doctors can't offer a cure. But getting an early diagnosis can be beneficial. Knowing what you can do is just as important as knowing what you can't do. If a person has another treatable condition that's causing the cognitive impairment or somehow complicating the impairment, then doctors can start treatments.

For those with Alzheimer's dementia, doctors can offer drug and nondrug interventions that may ease the burden of the disease. Doctors often prescribe drugs that may slow the decline in memory and other cognitive skills. You may also be able to participate in clinical trials.

Also, doctors can teach you and your caregivers about strategies to enhance your living environment, establish routines, plan activities and manage changes in skills to minimize the effect of the disease on your everyday life.

Importantly, an early diagnosis also helps you, your family and caregivers plan for the future. You'll have the chance to make informed decisions on a number of issues, such as:

  • Appropriate community services and resources
  • Options for residential and at-home care
  • Plans for handling financial issues
  • Expectations for future care and medical decisions

When a doctor tells you and your family members about an Alzheimer's diagnosis, he or she will help you understand Alzheimer's dementia, answer questions and explain what to expect. Doctors will explain what capacities are preserved and how to limit future disabilities, and look to keep you as healthy and safe as possible with the least disruption in your daily activities.

April 19, 2019 See more In-depth

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