Lewy body dementia Lewy body dementia affects around 10 percent of people with dementia. It’s caused by tiny, round deposits (Lewy bodies) that damage the nerve cells in the brain. This is linked with low levels of chemicals and loss of connections between nerve cells which then die. This causes the brain to function less well in sending and receiving messages. The effects can be patchy and sporadic, so someone with this type of dementia can vary quite a lot day to day. As well as affecting memory, people can have hallucinations, mobility problems including; physical stiffness, weaknesses in their arms and legs, and tremors. It is also related to Parkinson’s disease, so some people with Parkinson’s disease may develop this type of dementia, but people with Lewy body dementia don’t necessarily get symptoms of Parkinson’s disease.