Lewy body dementia, the second most common type of progressive dementia after Alzheimer's disease, causes a progressive decline in mental abilities.

It may also cause visual hallucinations, which generally take the form of objects, people or animals that aren't there. This can lead to unusual behavior such as having conversations with deceased loved ones.

Another indicator of Lewy body dementia may be significant fluctuations in alertness and attention, which may include daytime drowsiness or periods of staring into space. And, like Parkinson's disease, Lewy body dementia can result in rigid muscles, slowed movement and tremors.

In Lewy body dementia, protein deposits, called Lewy bodies, develop in nerve cells in regions of your brain involved in thinking, memory and movement (motor control).

Apr. 17, 2013