question: Lewy body dementia (Overview): Lewy body dementia, also known as dementia with Lewy bodies, is the second most common type of progressive dementia after Alzheimer's disease dementia. Protein deposits, called Lewy bodies, develop in nerve cells in the brain regions involved in thinking, memory and movement (motor control). Lewy body dementia causes a progressive decline in mental abilities. People with Lewy body dementia may experience visual hallucinations, and changes in alertness and attention. Other effects include Parkinson's disease-like symptoms such as rigid muscles, slow movement and tremors. Lewy body dementia care at Mayo Clinic