Diagnosis

A diagnosis of Lewy body dementia requires a progressive decline in your ability to think, as well as at least two of the following:

• Fluctuating alertness and thinking function
• Repeated visual hallucinations
• Parkinsonian symptoms
• REM sleep behavior disorder, 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 signs and symptoms, supports a Lewy body dementia diagnosis. So does sensitivity to antipsychotic drugs, particularly first-generation antipsychotics such as haloperidol (Haldol). Medications like Haldol aren't used for people with Lewy body dementia because they can cause a severe reaction.

No single test can diagnose Lewy body dementia. The diagnosis is based the on signs and symptoms you have and ruling out other conditions that can cause similar signs and symptoms. Tests might include:

Neurological and physical examination

Your doctor may check for signs of Parkinson's disease, strokes, tumors or other medical conditions that can affect the brain and physical function. A neurological examination tests:

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

Assessment of mental abilities

A short form of this test, which assesses your memory and thinking skills, can be done in less than 10 minutes in your doctor's office. It's not generally useful in distinguishing Lewy body dementia from Alzheimer's disease but can determine whether cognitive impairment is present. Longer tests that take several hours help identify Lewy body dementia.

Blood tests

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

Brain scans

Your doctor might order an MRI or CT scan to identify a stroke or bleeding and to rule out a tumor. While dementias are diagnosed based on the medical history and physical examination, certain features on imaging studies can suggest different types of dementia, such as Alzheimer's or Lewy body dementia.

If the diagnosis is unclear or the signs and symptoms aren't typical, your doctor might suggest additional imaging tests, including these that can support a diagnosis of Lewy body dementia:

• Fluorodeoxyglucose PET brain scans, which assess brain function.
• Single-photon emission computerized tomography (SPECT) or PET imaging, which can determine whether dopamine transporter uptake is reduced in the brain.

Sleep evaluation

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

Heart test

In some countries, doctors might also order a heart test called myocardial scintigraphy to check the blood flow to your heart for indications of Lewy body dementia. However, the test isn't used in the United States.

Emerging biomarkers

Research is ongoing into other indicators of Lewy body dementia. These biomarkers might eventually enable early diagnosis of Lewy body dementia before the full disease develops.