What tests are used to diagnose Alzheimer’s disease?
With thorough testing and a "process of elimination," doctors today can diagnose
probable Alzheimer’s disease with almost 90% accuracy. Alzheimer’s disease
cannot be definitely diagnosed until after death, when the brain can be closely
examined for certain microscopic changes caused by the disease.
The following diagnostic tools might be used to help
make a diagnosis of Alzheimer’s disease:
Patient history
A patient history helps the doctor assess an individual’s past and current
health situation. It also helps the doctor evaluate any medical problems,
develop a plan of treatment, and monitor the patient’s health over time. During
this evaluation, the doctor asks the patient a series of questions. A thorough
patient history includes:
- Patient age and sex
- Chief complaint
- History of current illness
- Past medical history
- Current health status
- Psychosocial history (marital status, living conditions, employment,
sexual history, significant life events)
- Mental status (memory, language, driving, judgment)
- Family history (including any illnesses that seem to run in the family)
- Review of systems (questions about current symptoms not included in the
client complaint)
Physical exam
The physical examination is part of the patient care process. The exam enables
the doctor to assess the overall physical condition of the patient. If the
patient has a medical complaint, the physical exam provides the doctor with more
information about the problem, which helps the doctor determine an appropriate
plan of treatment. The physical exam includes an examination of the following:
- Vital signs (temperature, blood pressure, pulse)
- Height and weight
- Skin
- Head, eyes, ears, nose
- Throat/neck
- Chest, including lungs and heart
- Breasts
- Abdomen
- Bones and muscles
- Nerves
- Rectal/genital area
Laboratory tests
When a doctor is diagnosing a disorder, he or she often orders laboratory tests
on certain fluids and tissue samples from the body. These tests can help
identify problems and diseases. There are hundreds of laboratory tests available
to help a doctor make a diagnosis. The most common are blood tests and
urinalysis. Blood tests involve a series of tests routinely done on blood to
look for abnormalities associated with various diseases and disorders. Blood
tests also might be used to look for the presence of a specific gene that has
been identified as a risk factor for Alzheimer’s disease. A urinalysis is a test
in which a urine sample is evaluated to detect abnormalities, such as improper
levels of sugar or protein. This test might be used by the doctor to help rule
out other disorders that might be causing symptoms similar to those of
Alzheimer’s disease.
Lumbar puncture/spinal tap
A lumbar puncture, also called a spinal tap, is a procedure in which the fluid
surrounding the spinal cord (called the cerebrospinal fluid or CSF) is withdrawn
through a needle and examined in a laboratory. Testing the CSF can help your
doctor diagnose disorders of the central nervous system (including multiple
sclerosis) that may involve the brain, spinal cord, or their coverings
(meninges).
Computed tomography (CT) scan
A computed tomography (CT) scan is a technique in which multiple X-rays of the
body are taken from different angles in a very short period of time. These
images are then fed into a computer, which creates a series of cross-sectional
"slices" of the body. Contrast material can be given to help differentiate
abnormal areas of the brain. CT imaging creates the images by measuring how
quickly the body and organs absorb the X-rays. CT scans often can reveal certain
changes that are characteristic of Alzheimer’s disease in its later stages.
These changes include a reduction in the size of the brain (atrophy), widened
indentations in the tissues, and enlargement of the fluid-filled chambers called
cerebral ventricles.
Magnetic resonance imaging (MRI)
Magnetic resonance imaging (MRI) is a test that produces very clear pictures, or
images, of the human body without using X-rays. Instead, MRI uses a large
magnet, radio waves, and a computer to produce these images. The MRI is a very
sensitive test that is very helpful for imaging "soft tissues," such as organs.
MRI is beneficial in ruling out other causes of dementia, such as tumors or
strokes. It also might help to show the physical and functional changes in the
brain that are associated with Alzheimer’s disease.
Electroencephalography (EEG)
Electroencephalography (EEG) is a medical imaging technique that measures brain
function by analyzing the electrical activity generated by the brain. This
activity is measured through special electrodes applied to the scalp. EEG is a
completely non-invasive procedure—meaning that nothing is inserted into the
body. EEGs can be used repeatedly in adults and children with virtually no risks
or limitations, and is helpful in the diagnosis of brain disorders. Because the
EEG procedure is non-invasive and painless, it often is used to study various
brain processes, such as perception, memory, attention, language, and emotion,
and is most helpful in identifying disorders that can mimic Alzheimer's
disease.
Electrocardiogram (ECG or EKG)
An electrocardiogram (EKG or ECG) is a recording of the heart's electrical
activity. This activity is registered as a graph or series of wavy lines on a
moving strip of paper. This gives the doctor important information about the
heart. For example, it can show the heart’s rate and rhythm. It also can help
show decreased blood flow, enlargement of the heart, or the presence of damage
due to a current or past heart attack. EKGs are non-invasive, quick, safe, and
painless, and are routinely done if a heart condition is suspected. This test
might be used by the doctor to help rule out other disorders that might be
causing symptoms similar to those of Alzheimer’s disease.
Neuropsychological testing
Neuropsychological testing studies the relationship between the brain and
behavior. It is used when the patient is having serious problems with short- and
long-term memory, attention and concentration, word and name association,
language understanding, and other symptoms that persist or worsen over time.
These tests help in the diagnosis and treatment of conditions that affect
thinking, emotion, and behavior. These include Alzheimer’s disease, various
psychiatric problems (depression, anxiety disorders), medication-related
conditions, substance abuse, strokes, and tumors. Neuropsychological tests
accompany a comprehensive interview with the patient, and might include tests to
assess attention, memory, language, the ability to plan and reason, and the
ability to modify behavior, as well as assessments of personality and emotional
stability. Neuropsychological testing also can help the doctor and family better
understand the impact of a disorder on a patient’s everyday functioning.
In addition, the following tests also might be done to
help diagnose and monitor the progression of Alzheimer’s disease:
Positron emission tomography (PET) scan
PET scanning is a three-dimensional imaging technique, utilizing the injection
of a radioactive tracer that allows a doctor to examine the heart, brain, or
other internal organs. PET scans can also show how the organs are functioning;
unlike X-ray, CT, or MRI, which show only body structure. PET is particularly
useful for the detection of cancer and coronary artery disease, and can provide
information to pinpoint and evaluate diseases of the brain. PET imaging can show
the region of the brain that is causing a patient to have seizures, and is
useful in evaluating degenerative brain diseases such as Alzheimer's,
Huntington's, and Parkinson's. PET scans can show the difference in brain
activity between a normal brain and one affected by Alzheimer’s disease. It can
also help differentiate Alzheimer's disease from other forms of dementia.
Amyloid imaging is a special type of PET scanning which shows deposits of
amyloid, a protein, in the brain.
Single photon emission computed tomography (SPECT)
scan
SPECT is a non-invasive technique for creating very clear, three-dimensional
pictures of a major organ, such as the brain or heart. SPECT scans use
radionuclide imaging – a technique that involves the injection of a very small
amount of a radioactive substance, called a tracer. Energy from the tracer in
the body is detected by a special camera, which then takes the pictures. SPECT
can map blood flow in certain regions of the brain, and is useful in evaluating
specific brain functions. This might reveal abnormalities that are
characteristic of Alzheimer's disease. Dopamine transporter SPECT is a special
type of SPECT used in Parkinson’s disease and Lewy body dementia.
Magnetic resonance spectroscopy imaging (MRSI)
MRSI is a test that allows the doctor to observe certain substances throughout
the brain without the use of radioactive materials. MRSI is a non-invasive
imaging technique that is used to study metabolic changes in brain tumors,
strokes, seizure disorders, Alzheimer's disease, depression, and other diseases
affecting the brain. It also has been used to study the metabolism of other
organs. MRSI can be done as part of a routine MRI, but they are different tests.
An MRI creates an image, and an MRSI creates a graph of the types and quantity
of chemicals in the brain or other organs.
References
National Institute on Aging: Alzheimer’s Disease
Education and Referral Center. Diagnosis.
www.nia.nih.gov/Alzheimers/AlzheimersInformation/Diagnosis/
Accessed 8/22/2011
Alzheimer’s Association. Diagnosing Alzheimer’s
www.alz.org/alzheimers_disease_diagnosis.asp Accessed 8/22/2011
Alzheimer’s Foundation of America. About Alzheimer’s:
Diagnosis
www.alzfdn.org/AboutAlzheimers/diagnosis.html Accessed
8/22/2011
© Copyright 1995-2011 The Cleveland Clinic Foundation. All rights reserved.
Can't find the health information you’re looking for?
This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 6/27/2011…#9176
