Tests and diagnosis

By Mayo Clinic Staff

To be diagnosed with Lewy body dementia, you must have experienced a progressive decline in your ability to think, as well as two of the following:

  • Fluctuating alertness and thinking (cognitive) function
  • Repeated visual hallucinations
  • Parkinsonian symptoms

In addition, one or more of the following features are considered supportive of the diagnosis of Lewy body dementia:

  • REM sleep behavior disorder, a condition in which people act out their dreams during sleep
  • Autonomic dysfunction, which involves instability in blood pressure and heart rate, poor regulation of body temperature, sweating, and related symptoms

No single test can diagnose Lewy body dementia. Instead, doctors diagnose your condition through ruling out other conditions that may cause similar signs and symptoms. Tests may include:

Neurological and physical examination

As part of your physical examination, your doctor may also check for signs of Parkinson's disease, strokes, tumors or other medical conditions that can impair brain function as well as physical function. The neurological examination may test:

  • Reflexes
  • Eye movements
  • Balance
  • Sense of touch

Assessment of mental abilities

A short form of this type of test, which assesses your memory and thinking skills, can be done in less than 10 minutes in your doctor's office but is generally not useful in distinguishing Lewy body dementia from Alzheimer's disease. Longer forms of neuropsychological testing can take several hours, but these tests help identify your condition.

Your results are then compared with those of people from a similar age and education level. This can help distinguish normal from abnormal cognitive aging, and may help identify patterns in cognitive functions that provide clues to the underlying condition.

Blood tests

Simple blood tests can rule out physical problems that can affect brain function, such as vitamin B-12 deficiency or an underactive thyroid gland.

Electroencephalogram (EEG)

If your confusion comes and goes, your doctor may suggest an EEG. This test can help determine if your symptoms may be caused by seizures or Creutzfeldt-Jakob disease, a rare, degenerative brain disorder that leads to dementia. This painless test records the electrical activity in your brain via wires attached to your scalp.

Brain scans

Your doctor may order an MRI, PET or CT scan to check for evidence of Alzheimer's disease, stroke or bleeding, and to rule out the possibility of a tumor.

Your doctor may order a sleep evaluation to assess for REM sleep behavior disorder or an autonomic function test to look for signs of heart rate and blood pressure instability.

April 17, 2013