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Cognition and Parkinsonís: What Youíve Always Wanted to Know
By Alexander Tröster, Ph.D.
Traditionally, Parkinson’s disease (PD) has been known as a movement disorder, characterized by such symptoms as tremor and slowness of movement. Increasingly, it is becoming recognized also for its nonmotor characteristics, including cognitive difficulties. For many people with Parkinson’s, these problems can be especially distressing, and can also be among the toughest to bring up with their doctor and their families.
Cognition is a bit difficult to define, because it covers several different mental skills and activities. It generally refers to the brain processes through which we discover and understand the world around us, and how we apply that knowledge from day to day. These include: making sense of perceptions; storing and retrieving memories; learning things; forming concepts; solving problems; planning activities; language; achieving insights; and abstract thinking.
What follows is an outline of the cognitive changes common in PD and what you and your loved ones can do to cope with them most effectively.
Cognitive Changes in Parkinson’s
Understanding just how many people with Parkinson’s experience cognitive changes is difficult, in part because the changes themselves are difficult to measure. Studies have reported highly varying estimates because they have used different means to identify and define impairments and selected study participants in different ways. It is estimated that, at any given time, of all people with Parkinson’s, about one quarter to one third have mild cognitive impairment (MCI) while another one quarter to one third have dementia.
Symptoms of MCI are mild and will not interfere with a person’s ability to function at home and work. They may not even be noticeable, but can be detected through testing. Doctors used to believe that cognitive changes did not develop until mid- to late-stage Parkinson’s, but recent research suggests that mild changes may be present as early as the time of diagnosis.
Dementia is a decline in multiple mental abilities, including but not limited to memory, which is sufficiently severe to lead to trouble at home or at work, or in social situations. As a result, people have difficulty caring for themselves. If one follows a large number of individuals with Parkinson’s over time, many may go on to develop dementia.
Causes of Cognitive Changes
What causes cognitive changes in people with Parkinson’s? One cause is a drop in the level of dopamine, the neurotransmitter that is involved in regulating the body’s movements. However, the cognitive changes associated with dopamine declines are typically mild and circumscribed.
Other brain changes are likely also involved in cognitive decline in Parkinson’s. Scientists are looking at changes in two other chemical messengers — acetylcholine and norepinephrine — as possible additional causes of memory and executive function loss in Parkinson’s.
Effects of Cognitive Changes
The cognitive changes that accompany Parkinson’s early on tend to be limited to one or two mental areas, or domains, and their severity will vary from person to person. The domains most often affected include:
Executive functions. Analogous to the problem-solving duties of an executive in a company, executive functions include such activities as forming concepts, making plans, formulating goals, anticipating consequences, strategizing to reach goals and evaluating progress.
Attention difficulties. Cognitive changes in PD may make it difficult to pay attention. In situations, such as a party, where several conversations are going on at once, this problem may be particularly acute.
Slowed thinking. People with PD may say their brain feels “swampy.” It takes longer for them to complete tasks, and it takes more effort than usual to complete them. This can mean that a project that once took one or two weeks to finish may now take three weeks or more.
Word-finding. People with PD may have difficulty coming up with words because of slowed thinking ability, not because those words are lost, as happens in Alzheimer’s disease. The words are available, but may be difficult to access quickly or efficiently. If you think of your vocabulary as a dictionary, the person with PD has to search for the dictionary before opening it to find the words, whereas for a person with Alzheimer’s, the dictionary is available but many of the pages are blank.
Learning and remembering information. About half to two-thirds of people with Parkinson’s report that they have memory problems. There are two types of memory, the first being declarative memory (e.g., remembering events from a specific time or place or facts). The second type of memory is non-declarative — that is, it is demonstrated through performance of tasks (e.g., riding a bicycle). Memory also involves at least three processes: encoding, storage and retrieval. Think of memory as a filing cabinet: first you have to acquire the information, and then you have to organize it and store it so that nothing falls out, and finally you have to retrieve it. People with PD have trouble taking in information and organizing it well, so it becomes difficult for them to remember it later.
Another specific type of memory is prospective memory. Failures of prospective memory annoy most of us, but seem to be more common in PD. For example, in the evening you put a package out to mail in the morning, but then find yourself leaving the house without sending it.
Imagery and spatial processes. The ability to form a mental image and to determine where things are in space — relative to oneself or to one another — may be affected by PD. An example of this problem is when one is driving a car, trying to form a mental map of which turns to take in order to get from home to the grocery store.
Seeking Help for Cognitive Changes
Cognitive change is a sensitive issue. In fact, the doctor is often as hesitant to address this subject as the person with Parkinson’s is to ask about it. Sometimes, the doctor will delay discussing the possibility of cognitive impairment out of concern for the person who is still coping with the shock of a new Parkinson’s diagnosis or because the person is struggling with motor symptoms such as stiffness and slowness.
For this reason, the person with Parkinson’s often needs to be the one to initiate the conversation. If the person is experiencing problems that are upsetting the family, or causing problems at work, one should discuss them with the doctor. Individuals with Parkinson’s should not tell themselves that these problems are too mild to bring up. The doctor can provide ways to help, beginning perhaps with a referral to a psychiatrist, a neuropsychologist, a speech or occupational therapist for further evaluation and assistance. The neuropsychological evaluation can be particularly useful, especially in the early stages of a cognitive problem. Having this baseline test can help the doctor determine whether future changes are related to medications, to the progression of the PD itself or to other factors such as depression.
Treating Cognitive Changes in PD
When a person reports symptoms of mild cognitive impairment, the doctor will first want to rule out causes other than PD, such as Vitamin B-12 deficiency, depression, fatigue, or sleep disturbances. It should be noted that PD does not cause sudden changes in mental functioning. If someone does experience a sudden change, the cause is likely to be something else, such as a side-effect of medication.
If it does turn out that the cognitive symptoms are traceable to Parkinson’s, there are drug therapies available. All of these were developed for Alzheimer’s, but they have been found to have some effect in Parkinson’s as well. One is rivastigmine, the only medication that has been approved by the US Food and Drug Administration (FDA) for dementia in PD. Doctors also may prescribe donepezil and galantamine. In addition, a person with attention difficulties that are due to daytime sleepiness may benefit from stimulants.
Much remains to be learned about the basic biology that underlies cognitive changes in PD. Researchers are working toward the development of diagnostic tests to identify people who seem to be at greatest risk for cognitive changes, and to differentiate cognitive problems in people with PD from those that occur in another disorder — related but different — known as dementia with Lewy bodies. Our two greatest hopes are that we will be able to be able to detect cognitive impairment early, and then have more therapies to treat it.
Dr. Tröster is Professor of Neurology at the University of North Carolina-Chapel Hill.
Tips for Care Partners
- Offer help only when your loved one asks for it
- Prompt the person — for example, instead of asking, “Did anyone call?” ask, “Did Linda call?”
- Say the name of the person and make eye contact when speaking to them, to gain and hold their attention
- Put reminder notes in a prominent place
- Keep things in routine places
- To ensure medications are taken on time, provide the person with a dispenser, perhaps with a built-in alarm
- Use photos on cell phone contact entries to prompt face-name association
- Write lists and keep them in a routine place
- If the person is searching for a word, provide a cue, such as, “the word you are looking for probably begins with ‘d’”
- Do not finish the sentences of a person who needs more time to put them together
- When presenting the person with a list of actions, first verbalize them, then write them down
- Ask the person questions in order to moderate the pace of conversation and allow them an opportunity to pause, catch up, think and reinforce
Catch up on PD ExpertBriefings
Dr. Tröster first presented this topic at one of PDF’s PD ExpertBriefings. If you missed the six-part series in 2011, just order a set of free DVDs or watch online at anytime.