Making the Diagnosis of Alzheimer's Disease
Positron Emission Tomography (PET)
According to guidelines from the Society of Nuclear Medicine and Molecular Imaging and the Alzheimer's Association, PET scans of the brain can help diagnose Alzheimer's disease in some people. PET technology creates images of beta amyloid plaque buildup in the brain, a key characteristic in Alzheimer's disease. According to the guidelines, the test may be appropriate for:
- Those who complain of persistent or progressive unexplained memory problems or confusion and who demonstrate impairments using standard tests of cognition and memory.
- Individuals meeting tests for possible Alzheimer's, but who have unusual symptoms.
- Individuals with progressive dementia and an early age of onset (before age 65).
Electroencephalography (EEG) is a medical 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 can be used repeatedly in adults and children with virtually no risks and is helpful in diagnosing seizures, which may be contributing to behavioral changes seen in the patient.
An electrocardiogram (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. This test may be used by the doctor to help rule out other conditions that may be causing symptoms similar to those of Alzheimer's disease.
Neuropsychological testing studies the relationship between the brain and behavior. It is used when the patient is having serious problems with memory, concentration, remembering words and names, understanding language, visual-spatial issues, and a variety of other symptoms. These tests help in the diagnosis and treatment of conditions that affect thinking, emotion, and behavior. These include Alzheimer's disease, various psychiatric problems, like depression and anxiety, problems caused by medicines, substance abuse, strokes, and tumors. Neuropsychological tests accompany a comprehensive interview with the patient and may include tests to assess 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 effect of a disorder on a patient's everyday functioning.
There are additional tests that may be done to help diagnose and monitor the progression of Alzheimer's disease. Most of the following tests are not done routinely and are more often used for research purposes:
Positron Emission Tomography (PET) Scan
PET scanning is a three-dimensional imaging technique that allows a doctor to examine the heart, brain, or other internal organs. PET scans also can 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 brain diseases like 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 help differentiate Alzheimer's disease from similar forms of dementia as well. PET scans are also able to estimate protein plaque density in the brains of patients with cognitive impairment. Build up of such plaques are found in patients with Alzheimer's, however, such tests don't replace current methods of diagnosing Alzheimer's and don't predict dementia.