Dementia Tests

Medically reviewed by Jennifer Monti, MPH, MDWritten by Wendy Leonard, MPH on May 11, 2011

Dementia encompasses a wide range of brain disorders that lead to cognitive impairment (such as a loss of thinking, remembering, and reasoning skills) that becomes severe enough to interfere with a person's daily life and activities. And while by far, the most common causes for dementia are Alzheimer’s disease and vascular dementia, there are many other possible causes, both neurodegenerative and non-neurodegenerative, as well as conditions that mimic dementia-like symptoms.

Thus, there are a number of tests that will likely be conducted in addition to requisite physical and patient history components. These include brain imaging, genetic testing, neurological testing, and various other lab tests.

Types of Brain Imaging

MRI (Magnetic Resonance Imaging)

Using powerful magnets and radio waves, this is a pain-free, noninvasive test that takes multiple images of the brain. It can help detect cysts, tumors, bleeding, swelling, developmental and structural abnormalities, infections, inflammatory conditions, or problems with the blood vessels. 

You need only lie down on table that slides into the MRI machine. You may be given a contrast dye (usually injected into your arm) to enhance the images. You may also be asked to wear a hospital gown, and will certainly be asked to remove all metallic objects from your body, such as jewelry, eyeglasses, watches, hairpins, and zippers. In terms of preparation, you may be asked to fast (not eat or drink anything) for four to six hours prior to the MRI. Generally speaking, you can expect this test to take over an hour.

CT (Computed Tomography) Scan

Utilizing x-ray technology, a CT scan is a pain-free, noninvasive test that creates multiple images of the brain. It’s used to help detect things such as bleeding in the brain, inflammation, skull fractures, blood clots, strokes, brain tumors, enlarged brain cavities and other signs of disease.

And just like the MRI, you need only lie down on a table that slides into the CT machine. You will be told to lie very still; and, you may also be told to hold your breath for short periods of time. You may be given a contrast dye (usually injected into your arm) to enhance the images. You may be asked to wear a hospital gown. You will also likely be asked to remove all metallic objects from your body (but not because of magnetism issues, but rather, because x-rays have difficulty passing through metal). In terms of preparation, you may be asked to fast (not eat or drink anything) for four to six hours prior to the CT scan. Generally speaking, you can expect this test to last just a few minutes.

PET (Positron Emission Tomography) Scan

Unlike MRI and CT scans, which reveal the structure of the brain, a PET scan is an imaging test that can also provide information on how the brain and its tissues are actually functioning—right down to the cellular level. It’s used to detect changes in glucose metabolism, oxygen metabolism, and blood flow, all of which can reveal abnormalities of brain function.

Again, just like the MRI and CT scan, you need only lie down on a table that slides into the PET machine. About an hour prior to the PET, a small amount of radioactive material (called a tracer) will be injected into a vein in your arm, or you will inhale it. You may be asked to perform various mental tasks such as reading or naming letters, as this diagnostic tool allows the doctor to see levels of brain activity. Being required to fast for four to six hours prior to the test is not unusual. This test takes between 30 minutes and two hours, on average.

Research studies have shown that, in some people, amyloid plaque buildup can be detected with PET scan technology even before symptoms are evident. However, it’s still unknown if these plaques are risk factors, causal, the result, or some combination thereof. Thus, utilizing PET scans as an early detection diagnostic tool is still being developed and standardized, and isn’t ready for use by clinicians in general practice.  

Important Note: If you have diabetes, be sure to share that information with your doctor. Blood sugar or insulin levels may affect the PET scan test results.

Genetic Testing (Blood Tests)

A genetic component is associated with a number of dementias. We have the technology to test for a select few. For example, we now know of ten genes forms (called alleles) believed to be associated with Alzheimer’s disease (AD), the most notable being the gene apolipoprotein E (APOE).

However, genetic blood tests do not provide a definitive diagnosis. Rather, having any given “dementia gene” only increases your risk; it doesn’t mean you have it. In fact, there are plenty of people who have the AD-specific E (APOE) allele who never develop AD.

That being said, people who suffer from the (very rare) early onset form of AD who have mutations in three specific genes—namely APP (on chromosome 21), PSEN-1 (on chromosome 14) and PSEN-2 (on chromosome 1)—tend to develop early onset AD. However, there are also people who suffer from early onset AD who don’t have any of these genes.

Neuropsychological Testing

The most commonly used neuropsychological test is the Mini-Mental State Exam (MMSE). During the MMSE, you will be asked questions and given instructions designed to evaluate your basic cognitive (mental) status. For example, you may be asked today’s date and when your birthday is. You may also be asked to repeat a list of words or phrases, and to count backwards from 100 by sevens. No advanced preparation is needed for this test.

Lab Tests

There are many causes of dementia and/or dementia-like symptoms. The following laboratory tests may help identify (or at least rule out) many of these possible causes:

Infectious Causes

  • Syphilis test (RPR or VDRL)
  • lyme titer
  • HIV antibody
  • cryptococcus antibody
  • HSV antibody
  • polymerase chain reaction for Whipple disease

Nutritional Causes—Vitamin Deficiencies

  • vitamin B3 (niacin)
  • vitamin B6
  • vitamin B12
  • vitamin E
  • vitamin D
  • folate
  • pre-albumin studies for malnutrition

Electrolyte Abnormalities

  • sodium
  • calcium
  • magnesium
  • phosphorus

Metabolic Causes

  • serum ammonia
  • serum volatiles
  • glucose levels

Hormonal Causes

  • thyroid studies
  • diabetes testing
  • cortisol testing

Abnormal Proteins and Systemic Inflammatory Disorders

  • serum protein electrophoresis
  • urine protein electrophoresis
  • ESR, CRP

Autoimmune Causes

  • ESR
  • rheumatoid factor (RF)
  • antinuclear antibody (ANA)
  • lupus anticoagulant assay

Psychiatric Evaluation

A psychiatric evaluation should be conducted to determine if depression or another psychiatric disorder may be causing or contributing to a person's symptoms. The exact nature of the psychiatric evaluation(s) greatly depends upon the presenting symptoms. 

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