Alzheimer's Disease

Diagnosis

No single test can detect Alzheimer's. Instead, the disease is diagnosed by symptoms, findings on neurologic examination, and results from diagnostic tests. These tests help exclude other conditions that might cause the signs and symptoms.

A diagnosis of Alzheimer's may be "probable," meaning that other causes of the symptoms have been ruled out and the most likely cause is Alzheimer's disease.

First, the patient will have a complete physical exam, along with a detailed history of symptoms and medical history, including medications. Examination by neurology specialists will help identify signs of Parkinson's disease, strokes, tumors and other medical conditions that may impair memory and thinking, as well as physical function. Tests may include:

Tests

Mental status and neuropsychological assessments — To determine which thinking and memory functions may be affected and to what degree, the patient will be asked questions to measure cognitive functions for attention, learning, recall, language and visuospatial abilities. The tests are compared to the tests of other patients of similar age and education.

The patient and people familiar with the patient will be interviewed about the patient's emotional state and day-to-day routines. They will also be asked about possible alcohol or drug abuse, head trauma and other causes for memory loss. Family members or close friends can provide valuable information about how the patient's behavior and personality have changed.

Psychiatric assessments — In addition, the patient may have a psychiatric assessment to uncover possible depression or other mental illness.

Blood tests — The patient's blood will be checked for infections or conditions such as vitamin deficiency, anemia, medication levels, disorders of the thyroid, kidneys or liver, and other factors that can cause memory loss.

Brain imaging — Internal images of the brain help detect strokes, tumors or other conditions that may have affected the brain. Brain images can show changes to structures in the brain that are associated with memory, such as the hippocampus. Brain imaging techniques offered at Mayo Clinic are:

• Computed tomography (CT scan) — In this test, an X-ray machine rapidly rotates around the brain while taking a series of thin X-ray beams that produce two-dimensional images.
• Magnetic resonance imaging (MRI) — This test uses powerful magnets and radio waves to produce a detailed, three-dimensional view of the brain. Most patients are asked to undergo an MRI scan. Depending on the individual, another scan technique may be performed.
• Positive emission tomography (PET) or single-photon emission computerized tomography (SPECT) — These two fairly new techniques may be needed for clinical-related or research-related study. For both tests, a small amount of radioactive material is injected into the patient and emission detectors are placed on the brain. PET provides visual images of brain activity. SPECT is used to measure blood flow to various regions of the brain.

Other tests that sometimes provide important diagnostic information include electroencephalogram (EEG), electromyogram (EMG), urine tests, and tests on cerebrospinal fluid (CSF) obtained by a lumbar puncture. Physicians discuss with the patient and family which tests are most appropriate to establish the correct diagnosis.