Parkinson’s Disease is a common disorder of deep brain structures that help control movement. Over time, many people with Parkinson’s disease develop Parkinson’s Disease Dementia. The majority of Parkinson’s Disease patients over the age if 65 develop dementia within a few years. Even younger people with Parkinson’s Disease can develop dementia – one community – based study found that just over one person in ten with Parkinson’s Disease between the ages of 50 and 60 had already developed dementia.
In Parkinson’s disease, an abnormal Protein accumulates inside neurons in deep brain structures known as the substantia nigra. This abnormal accumulation of what is called “alpha-synuclein” was first described by a Professor Lewy and still bears the name of being a “Lewy body”. Lewy bodies are also seen outside the deep brain structures, in the thinking” parts of the brain in Parkinson’s Disease Dementia and in Lewy body dementia.
The main difference between Parkinson’s Disease dementia and Lewy Body dementia is a bit arbitrary. If motor symptoms come first, by at least a year, and dementia develops later, the convention is to call it Parkinson’s Disease dementia. If the motor symptoms follow the dementia symptoms, the convention is to call it Lewy Body dementia (or dementia with Lewy bodies”).
In Parkinson’s disease, one of the chief abnormalities is loss of the brain chemical (neurotransmitter) dopamine. The usual treatment consists of medications that can increase the levels of dopamine, either by supplying more of it, or by slowing its breakdown.
Symptoms of Parkinson’s Disease Dementia
Given that Alzheimer’s disease is so common, and its stages are so characteristic, one way to understand the symptoms of Parkinson’s Disease Dementia is that while they are similar to those of Alzheimer’s disease, they occur out of order. Early in the course of Parkinson’s disease dementia, mental slowing is seen. Another sign is mental inflexibility. Compared to people with Alzheimer’s disease, those with Parkinson’s disease dementia have somewhat worse visuospatial function, although at the early stages, this is usually demonstrated better by formal testing (such as the clock drawing task) than is seen in everyday life.
Hallucinations are often seen in Parkinson’s disease dementia. The hallucinations typically consist of seeing things that are not there. In Alzheimer’s disease, hallucinations generally occur late (e.g. in the severe stage), but in Parkinson’s Disease dementia, they usually occur early (when the dementia is in the mild stage. In fact, in Parkinson’s disease dementia, hallucinations can be an early sign of dementia. Even when seen as a reaction to too much dopamine, they can be a sign of dementia to follow later.
Symptoms that are more specific for Parkinson’s Disease dementia are a mild memory impairment that at first responds to hints and cues. just as in Lewy Body dementia, patients with Parkinson’s Disease dementia can show large changes in attention and alertness from day to day (one day they are able to hold conversation, next day the cannot). Other manifestations of fluctuation in symptoms are episodes of starring blankly, especially if if occurs to such an extent that you find yourself touching or even shaking the person you care for so that they will “snap out of it”. Daytime sleepiness can be another sign of fluctuation. Sometimes, for reasons that are not clear, the fluctuation in alertness can be made better by making changes to medications that smooth out the level of dopamine.
Course of Parkinson’s Disease Dementia
Parkinson’s Disease dementia is a progressive disorder that has an average length of several years from the beginning of symptoms. One of the notable features of Parkinson’s Disease dementia is that people can respond very well to treatment with cholinesterase inhibitors. The evidence is best for rivastigmine (tradename: ExelonTM). If for some reason that does not work, others can be tried. For some patients, the response to a cholinesterase inhibitor is dramatic improvement. Click here to read Rivistigmine for dementia associated with Parkinson’s disease by Emre M., Aarsland D., Albanese A., et al., as was published in the New England Journal of Medicine in 2004.
The cause of Parkinson’s disease dementia is still unknown, but it is thought that there are many genes which contribute to the development, including some that are also thought to cause Alzheimer’s disease. Diagnostic criteria for Parkinson’s Disease dementia has been proposed recently, but still requires prospective validation before they can be recommended for widespread use. Click here to read Clinical diagnostic criteria for dementia associated with parkinson’s disease by Emre M., Aarsland D., Brown R., et al., as was published in Movement Disorders in 2007.
Frequently Asked Questions about Parkinson’s Disease dementia:
Exactly what is a Lewy Body?
Early descriptions of Lewy Bodies called them “debris”, but a considerable body of work has revealed that they are made up of a particular type of protein called alpha-synuclein. This protein is otherwise an important part of the synapse – i.e., the small space that separates two neurons, by which they “talk” to each other. The “talking” takes the form of releasing a neurochemical across the synapse, which induces an electrical charge in the second neuron (the one receiving the chemical signal) from the first (the one transmitting it). This is what the term “synaptic neurotransmission” means, and is why the chemicals that cross the synapse are called “neurotransmitters”.
How does Lewy Body dementia differ from Parkinson’s disease dementia?
There is a fairly arbitrary rule that if patients have the classic motor symptoms of Parkinson’s disease (these are tremor, moving slowly, rigid muscles and a tendency to fall) for more than a year before they have cognitive symptoms (such as impaired memory, inattention or hallucinations) the dementia is called Parkinson’s Disease dementia. On the other hand, if the cognitive symptoms occur first and then the motor symptoms, then the dementia is more than likely Lewy Body dementia.
Do the symptoms of Parkinson’s Disease dementia include depression?
Not always, but depression occurs often, and is a major cause of disability. The symptoms can overlap, but signs of depression (low mood, disrupted sleep, weight loss, poor appetite, inability to enjoy things, inability to think anything positive about the future) should be treated. Which anti-depressant to use in the setting of Parkinson’s Disease dementia (or Lewy Body dementia) is not clear, although there is a theoretical basis to favour those that increase the level of the neurotransmitter noradrenaline. this is where a skilled psychiatrist can be especially useful. Criteria for diagnosing depression in people with Parkinson’s Disease were proposed in 2007, but still are in the process of being validated. Click here to read Depression rating scales in Parkinson’s Disease: critique and recommendations by Schrag A., Barone P., Brown R.G., et al, as was published in Movement Disorders in 2007.
Parkinson’s Disease can be a debilitating disease which causes a person to experience tremors at the onset and be rigid at the later stages of the disease. It is relatively common for dementia to develop in a person who has been diagnosed with Parkinson’s disease. This is not the same as when symptoms similar to those experienced in Parkinson’s disease appear in a person who has been diagnosed with dementia. When this happens, it is called Parkinsonism.
There is no evidence that Parkinson’s disease occurs more often in a certain race or ethnic group. However, it has been found that older men develop Parkinson’s almost twice as often as do older women. Patients with Parkinson’s disease are more likely to develop dementia if their diagnosis occurs when they are 70-years of age or older. There are many estimates of how often dementia develops with Parkinson’s disease. A study in New York City found that 19.2% of patients with Parkinson’s disease developed dementia when followed up after two years. In Scotland, a study which observed 249 patients found that 23.6% of patients developed Parkinson’s disease developed dementia.
Patients with Parkinson’s disease and dementia experience short-term and long-term memory loss similar to those with Alzheimer’s disease. In contrast though, they seem to do better on recognition tasks than patients with Alzheimer’s disease do. It is believed that mortality may be higher in patients with Parkinson’s disease and dementia, as compared to those with one or the other. Patients with Parkinson’s disease, dementia and depression have even more severe disabilities and tend to experience an even faster cognition_decline. There is currently no cure for Parkinson’s disease, but there are treatments available to improve symptoms, often for several years.