Neuroimaging and Biomarkers: How Early Can We Diagnose Alzheimer's?



Dementia: Diagnosis Is a Complex Process

Doctors use a variety of methods to arrive at a dementia diagnosis.
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Patients concerned about changes in how they think, feel, and behave tend to go to their family doctor for a diagnosis.

However, in the case of dementia, a more accurate diagnosis will likely come from a neurologist — a specialist in disorders of the brain and nervous system. In some cases the right diagnostician might be a geriatric psychiatrist, a neuropsychologist, or a geriatrician. (1)

Diagnosing dementia and the brain changes that cause it generally involves a medical history, a physical exam, lab tests, and neuropsychological assessments.

Doctors can usually diagnose dementia with a high degree of confidence. Identifying the underlying diseases, however, can be challenging.

Identifying the Reason for Dementia Helps Identify Treatment Options

One complication is that symptoms of different conditions can overlap, or people may have more than one type of dementia at the same time.

Despite these difficulties, getting an accurate diagnosis is an essential first step in getting the care one needs.

For example, people with Lewy body dementia may respond well to medications formulated to reduce cognitive symptoms of Alzheimer’s. In fact, they may do even better on these drugs than Alzheimer’s patients.

However, they may respond more poorly to medications created to reduce behavioral or movement symptoms of Alzheimer’s or Parkinson’s. What’s more, for patients with Lewy body dementia, the side effects of these drugs can be dangerous or cause permanent damage. (2)

First Step: Ruling Out Conditions That Can Mimic Dementia

One of the first priorities in diagnosing any type of dementia is ruling out treatable or reversible conditions with similar symptoms. These include:

  • Depression
  • Side effects of medication
  • Excessive alcohol consumption
  • Thyroid problems
  • Vitamin deficiencies, such as inadequate amounts of B12 (3)

Is It Possible to Detect Dementia Before Symptom Onset?

Researchers are working to develop tests that can identify people on course to develop dementia before the onset of symptoms. They are also working to diagnosis dementia at its earliest stages, with the goal of staving off brain damage.

Part of this effort involves a search for biomarkers — indicators of disease that can be measured accurately and reliably, such as changes in sensory abilities or substances in blood, cerebrospinal liquid, or urine.

For example, a study published in the December 2019 issue ofAlzheimer’s & Dementiafound an association between levels of anthranilic acid in blood plasma and a higher risk of developing dementia and Alzheimer’s. More research on this connection is needed. (4)

Diagnosing Vascular Dementia: A Judgment Call

There is currently no definitive test for vascular dementia and no way to diagnose it conclusively except autopsy. Doctors make a judgment call on the basis of information the patient provides, a medical history of stroke or other cardiovascular disorders, and a battery of tests.

To gauge the health of the heart and blood vessels, doctors measure:

  • Blood pressure
  • Cholesterol
  • Blood sugar

To evaluate the overall health of the neurological system, doctors check:

  • Reflexes
  • Muscle tone and strength, comparing one side of the body to the other
  • Ability to get up from a chair and walk across the room
  • Sense of touch and sight
  • Coordination
  • Balance

To look for visible abnormalities in the brain, doctors might recommend one of the following imaging procedures:

To look for any potential blockage in the carotid artery, which supplies blood to the brain, doctors might use:

  • Carotid ultrasound High-frequency sound waves are used look for structural problems or narrowing of the artery due to plaque deposits.
  • Doppler ultrasound The test reveals the movement of blood through the arteries as well as structural features.

To assess cognitive skills, doctors use neuropsychological tests to gauge the patient’s ability to:

  • Comprehend language, speak, and write
  • Work with numbers
  • Learn and recall information (this may be less challenging for people with vascular dementia than patients with Alzheimer’s)
  • Create a strategy to solve a problem (this may be especially difficult for people with vascular dementia)
  • Come up with appropriate responses to hypothetical situations (5)

Lewy Body Dementia: Symptoms Can Be Mistaken for Other Disorders

Diagnosing Lewy body dementia is especially complicated because its symptoms are similar to those of Alzheimer’s, Parkinson’s disease, or a psychiatric illness.

As a way to distinguish Lewy body dementia from other brain disorders, researchers are studying a number of methods, including the use of lumbar puncture (also known as a spinal tap) to measure proteins in cerebrospinal fluid. (6)

Cognitive decline is one of the essential criteria for a diagnosis of Lewy body dementia. In addition, two or more of the following are required:

  • Fluctuating, unpredictable alertness and ability to think
  • Repeated visual hallucinations
  • Parkinsonian symptoms, such as physical rigidity
  • REM sleep behavior disorder, in which patients act out their dreams while asleep

Physicians may also look for the presence of certain biomarkers and conduct other tests to assess brain function. These include:

The presence of the following symptoms may also indicate Lewy body dementia:

  • Problems with autonomic nervous system function, as indicated by unstable blood pressure and heart rate, poor regulation of body temperature, and sweating
  • Excessive daytime sleepiness
  • Loss of the sense of smell

To rule out other conditions with symptoms resembling those of Lewy body dementia, such as Parkinson’s disease, strokes, and tumors, doctors might conduct neurological and physical exams that assess:

  • Reflexes
  • Strength
  • Walking
  • Muscle tone
  • Eye movements
  • Balance
  • Sense of touch

Additional tests to rule out other types of dementia might include:

  • An MRI, PET, or CT scan. These may identify brain changes unique to Lewy body dementia and rule out the possibility of a tumor
  • An extended version of a test to assess cognition and memory can reveal disordered thinking characteristic of Lewy body dementia

Related:8 Facts You Should Know About Parkinson's Disease and Psychosis

Diagnosis Is Difficult in the Earliest Stages

This dementia can be particularly difficult to diagnose in its early stages, as its symptoms resemble those of other forms of dementia.

What’s more, one particular type of frontotemporal disorder resembles depression or a stroke, especially when there are speech or movement problems.

As with other forms of dementia, researchers are working on new diagnostic methods involving biomarkers, brain imaging, and neuropsychological testing.

To assess reasoning and memory skills in enough detail to diagnose frontotemporal disorders, a physician may conduct a long neuropsychological test.

The physician may also order blood tests to rule out other conditions such as kidney or liver disease.

PET and other scans can also reveal more about what’s going on in the brain, revealing abnormalities in the frontal or temporal lobe.






Video: The Alzheimer Enigma: The Causes of the Dementia Epidemic | Albert Hofman || Radcliffe Institute

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Date: 05.12.2018, 22:05 / Views: 52443