Lewy body dementia (LBD) can be difficult to differentiate from PD dementia and is responsible for 15-20% of the cases of dementia. In general, if the dementia and PD symptoms such as slowness, stiffness, tremor, walking and balance problems occur within a year of each other, a diagnosis of LBD rather than PD dementia which occurs in the later stages of PD, is generally made. With LBD there is a progressive decline in cognitive abilities that is severe enough to interfere with activities of daily living. There are also often fluctuations in cognition with variability in attention and alertness. Visual hallucinations (seeing things that are not there) are also common. Other symptoms can include frequent falling, delusions such a paranoia or feelings of harm, REM sleep behavior disorder (acting out of dreams) and depression. Levodopa may be helpful in some patients, but they generally do not respond as well as those with PD. Cholinesterase inhibitors such as donepezil (Aricept) or rivastigmine (Exelon) may be helpful.