Amyloid PET Imaging and Other Diagnostic Tools used for Alzheimer’s Disease

Ever thought about how physicians arrive at a diagnosis of Alzheimer’s disease or other dementias?

beaker

Finding Alzheimer’s disease (AD) is often a game of ruling out other causes — are the memory problems due to AD or is it something else? Is it caused by depression, vitamin deficiency, stress, sleep disturbances, infection, etc., etc.? Or are the memory problems in fact being caused by Alzheimer’s disease? Unfortunately there is no pass/fail test that will tell us immediately whether or not the person has a diagnosis. Because of the uncertainty with diagnosis, even experienced physicians can make mistakes and mis-diagnosis is not unheard of.

Comprehensive Diagnosis

  • Subjective complaints
  • Cognitive Testing200400104-001
  • Medical History
  • Medical Tests (i.e. blood work and brain imaging)

Rule out

  • Disturbed sleep
  • Emotional disorders
  • Metabolic disorders
  • Eye and ear impairments
  • Nutritional deficiency
  • Tumors
  • Infections
  • Alcohol, drugs, or medication interactions

It used to be that brain autopsy was the only way to receive a definitive diagnosis of Alzheimer’s disease, but with improved testing this is no longer the case. Experienced clinicians have a 95% accuracy rate in diagnosis. Furthermore, physicians can now administer tests that measure specific biomarkers in the brain that help them to determine a diagnosis.

The formation of plaques and tangles in the brain are the two hallmarks of Alzheimer’s disease (AD). Plagues are composed of a protein, beta-amyloid, that abnormally clumps together in AD. Many nerve cells, also called neurons, die as the damage of AD spreads. Dead and dying nerve cells contain tangles, which are made up of a protein called tau. The tangles destroy a vital cell transport system in the brain.

Advances in research have produced certain diagnostic tools that measure levels of tau and beta-amyloid. For instance a clinician may analyze a patient’s cerebrospinal fluid (CSF) to look for these important biomarkers. CSF is a clear fluid that bathes and cushions the brain and spinal cord. Adults have about 1 pint of CSF, which physicians can sample through a minimally invasive procedure called a lumbar puncture, or spinal tap. Research suggests that Alzheimer’s disease in its earliest stages may cause changes in CSF.

Beta-amyloid is under significant scientific scrutiny, and amyloid-plaque formations can be found in all patients with AD. Progress in Alzheimer’s disease research and imaging has made it possible to detect beta-amyloid in the human brain using radioactive tracers and positron emission tomography (PET). See the picture of a PET scan below.

pet scan

Amyloid PET Imaging

Despite these noteworthy advances, bear in mind that spinal taps and PET scans are not a definitive diagnosis! They are simply tools designed to increase the clinical certainty of the physician’s conclusion. Also note, that these tests are often expensive and not covered by most health insurances. Furthermore, amyloid imaging is usually only conducted in limited situations when the patient’s symptoms are atypical (e.g. young age of disease onset, symptoms do not satisfy criteria for AD, etc.).

Learn more about the steps involved in a diagnosis here, or call our 24/7 Harry L. Nelson Helpline to speak to a live representative.

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