Lewy body dementia
What is it?
Lewy body dementia shares characteristics with both Alzheimer's disease and Parkinson's disease. Like Alzheimer's, it causes confusion. Like Parkinson's, it can result in rigid muscles, slowed movement and tremours.
But the most striking symptom of Lewy body dementia may be its visual hallucinations, which can be one of the first signs of the disorder. Hallucinations may range from abstract shapes or colours, to conversations with deceased loved ones.
In Lewy body dementia, abnormal round structures — called Lewy bodies — develop in regions of your brain involved in thinking and movement. While risk increases with age, Lewy body dementia is estimated to affect less than 1 percent of the population over the age of 65.
Lewy body dementia signs and symptoms may include:
- Visual hallucinations. Seeing colours, shapes, animals or people may be one of the first symptoms of Lewy body dementia.
- Movement disorders. Parkinson's-like signs may include slowed movement, rigid muscles, tremors or a shuffling walk.
- Delusions. These may consist of false ideas about another person or situation.
- Cognitive problems. Alzheimer's-like problems may include confusion, memory loss and reduced attention spans.
- Sleep difficulties. A sleep disorder can cause you to physically act out your dreams while you're asleep.
The cause of Lewy body dementia isn't known, but the disorder may be related to Alzheimer's or Parkinson's disease because:
- Lewy bodies contain a protein associated with Parkinson's disease.
- Lewy bodies often are found in the brains of people who have Parkinson's and other rare dementias.
- People who have Lewy bodies in their brains also often have the plaques and tangles associated with Alzheimer's disease.
Some scientists have suggested that there is a Lewy body variant of Alzheimer's disease. Conversely, Lewy body dementia and Alzheimer's may just coexist in some people.
Although the cause of Lewy body dementia isn't clear, several factors appear to increase the risk of developing the disease:
- Age. Most cases of Lewy body dementia occur in adults older than 60.
- Sex. Lewy body dementia appears to be more common in men.
- Heredity. If you have a family member with Lewy body dementia, you may be at increased risk of the disease.
After onset, Lewy body dementia typically causes severe dementia. The Parkinson's-like features and visual hallucinations tend to worsen with time. Average survival is about eight years after symptoms begin.
For the doctor to make a diagnosis of 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 cognition
- Repeated visual hallucinations
- Parkinson's-like symptoms
No single test can diagnose Lewy body dementia. Instead, doctors diagnose the disease through a process of elimination — ruling out other diseases and conditions that may cause similar signs and symptoms. Tests may include:
As part of your physical exam, 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 exam may test:
- Eye movements
- Sense of touch
Mental status exam
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. Longer forms of neuropsychological testing can take several hours. 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.
Simple blood tests can rule out physical problems that can affect brain function, such as vitamin B-12 deficiency or an underactive thyroid gland.
If your confusion comes and goes, your doctor may suggest an EEG. This test can help determine if your symptoms are better explained by seizures or Creutzfeldt-Jakob disease, a very rare degenerative brain disorder more commonly known as mad-cow disease. This painless test records the electrical activity in your brain via wires attached to your scalp.
Your doctor may order an MRI or CT scan to check for evidence of stroke or bleeding, and to rule out the possibility of a tumour.