Parkinson's Disease Dementia Overview

Parkinson's disease dementia (PDD) is a type of Lewy body dementia that occurs when a patient with Parkinson's disease develops progressive dementia at least two years after a diagnosis of Parkinson's disease has been made, and other causes of dementia have been ruled out. Approximately 25-30% of all patients with Parkinson's disease also have dementia, but after having Parkinson's disease for 15 years, the prevalence of PDD increases to 68%.

PDD is usually different in how it presents itself from Alzheimer's disease: In PDD, for example, people usually have major problems with attention, executive functioning, and memory retrieval. In Alzheimer's disease, the memory problem is more often one of storing memories. People with PDD may also be more aware of having a memory problem than people with Alzheimer's disease.

A key to identifying PDD is the development of cognitive problems that are severe enough to affect daily functioning. The Mini-Mental State Examination (MMSE) is a screening test that is often used to help diagnose both Alzheimer's disease and PDD.

Dementia is common in people with Parkinson's disease, especially since the average age of onset of Parkinson's disease is 60 and the longer a person has it, the more likely they are to develop dementia. Being male and having visual hallucinations are strong predictors of developing dementia in people with Parkinson's disease.

Another type of dementia in which visual hallucinations are common, and that is related to both Parkinson's and Alzheimer's diseases is called Lewy body dementia. In fact, Lewy bodies are found in the brains of people with PDD, Lewy body dementia, and even some people with Alzheimer's disease.

Presently, there is only one FDA-approved treatment for PDD. The Exelon patch (rivastigmine transdermal system) and Exelon (rivastigmine tartrate) capsules are indicated for the treatment of mild to moderate dementia of the Alzheimer’s type and mild to moderate dementia associated with Parkinson’s disease.