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Diagnosing Alzheimer’s Disease. Medical Testing and Cognitive Screening

According to the Society of Nuclear Medicine and Molecular Imaging, “Alzheimer’s Disease (AD) is not the only cause of forgetting things. AD is the leading cause of memory impairment and thinking difficulties among older people, but other medical conditions, such as thyroid issues, alcoholism, strokes, drug interactions, and vitamin deficiencies, can cause similar symptoms.

Unlike Alzheimer’s Disease, many of these conditions are treatable. Medications themselves can also cause side effects such as forgetfulness and thinking problems. So, if you have memory issues and other cognitive problems, it is important to find out what the reason is so you can best treat it.”

Medical testing

A diagnosis of Alzheimer’s Disease is made by determining the presence of certain symptoms and ruling out other causes of dementia. No single test can reveal whether or not a person has Alzheimer's disease. A doctor must complete a thorough medical evaluation, including a comprehensive medical history, family history, mental status testing, a physical assessment, a neurological exam, blood tests, and brain imaging exams.

Magnetic Resonance Imaging (MRI) is an imaging test that produces pictures of the brain’s structures and shows doctors how the parts work together. It can detect brain abnormalities associated with mild cognitive impairment (MCI) and can be used to predict patients with MCI who may eventually develop Alzheimer's disease. In the early stages of Alzheimer's disease, an MRI of the brain may be normal. However, in later stages, an MRI may show a decrease in the size of the temporal and parietal lobes.

At this point, it’s necessary to use more advanced testing. Brain changes can also be detected with a positron emission tomography (PET) scan. A PET scan uses a radioactive agent to show amyloid plaques or clumps of abnormal cells in the brain. This agent attaches to the plaques once it is injected into the person’s body. Then, the technician will take photographs of your brain so doctors can see the location and size of the plaques. If the scan does not show any plaques in the brain, it is less probable that you have AD.

Most elderly people will have plaque deposits that are not characteristic of Alzheimer’s. To an extent, this is age-related, so having amyloid plaques does not necessarily mean that you will develop Alzheimer’s in the future. This will only occur if you reach a certain threshold.

Positron emission tomography (PET)/computerized tomography (CT) scan of the head is another imaging tool used to differentiate Alzheimer's disease from other types of dementia and determine its severity. This test fuses the images from a PET and CT scan together to provide detail on both the anatomy (from the CT scan) and function (from the PET scan) of organs and tissues.

A single photon emission computed tomography (SPECT) is another type of scan used to tell the difference between Alzheimer’s Disease and other forms of dementia.

Cognitive screening

A person’s performance on cognitive tests can reveal cognitive problems but can only suggest Alzheimer’s Disease, not confirm its presence.

These brief screening tools focus on a wide range of thinking skills from basic orientation (who we are, when is it, and where we are) to more abstract thinking (the ability to think about objects, principles, and ideas that are not physically present).

Someone uses abstract thinking to create and understand humor or create something such as a new dish for dinner. Attention span, counting, object naming, memory, problem solving, spatial awareness, and language fall in between basic orientation and abstract thinking.

Spatial awareness (how shapes, spaces, and other areas relate to one another) is another aspect of cognition. An example of spatial awareness is knowing that a cup is on a table and not underneath it.

Each screening tool is slightly similar but also different in the exact questions and activities that they pose. Areas of difference may include how advanced the tool is, whether training is needed to administer it, how long it takes, educational requirements, language, and whether a fee is attached.

These cognitive screening tools may be administered by nurses, speech-language pathologists, occupational therapists, neurologists, psychologists,geriatricians, family practice physicians, and more.

Below are examples of questions or tasks an Alzheimer’s Disease screening tool may include and the areas of cognition it assesses.

The Mini Mental Status Examination (MMSE) for orientation: “What is the year, season, month, date of the month, and day of the week?”

Montreal Cognitive Test (MOCA) for naming: “Name these 3 animals.” Show pictures of (1) camel or dromedary, (2) lions, and (3) rhinoceroses in order.

General Practitioner Assessment of Cognition (GPCOG) for recall/memory: “I am going to give you a name and an address. After I have said them, I want you to repeat them. Remember this name and address because I am going to have you tell them to me again in a few minutes. The name and address are: John Brown, 42 West Street, Kensington.” Several minutes later, you will ask: “What was the name and address I asked you to remember?” The patient will have four attempts to recall this information.

Clock-Drawing test for spatial awareness: After giving the patient a preprinted circle, ask them to “put in all the numbers where they are supposed to go.” When that is completed, say: “Now, set the hands to 10 past 11.” Some clinicians do not provide a preprinted circle to avoid giving hints. Here is an example of a completed clock.

SAGE (Self-Administered Gerocognitive Examination) for counting and calculation: Ask the patient, "How many quarters equal $8.75?” The client or their caregiver can download a reprinted test form or can complete the form in their doctor’s office. The physician will then score the test. It should take someone an average of 10-15 minutes to take this test, but there is no time limit.

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