Thinking and memory problems are among the most worrisome potential Parkinson's symptoms. Given their significant impact on function and quality of life, understanding and treating the range of cognitive changes in Parkinson's is a top priority for researchers.
Thinking and memory (cognitive) symptoms are are common in Parkinson's, but not everyone experiences them. In some people, they are mild and don't impact work or daily activities. This is called "mild cognitive impairment." In others, they are more significant and affect the everyday activities of both the person experiencing them and their care partner. This is classified as "dementia." There are different aspects of thinking and memory, and people with Parkinson's most commonly notice difficulty with:
- Paying attention or concentrating
examples: reading a book, participating in group conversations
- Multitasking and problem solving (executive function)
examples: juggling multiple ongoing projects, figuring out solutions such as how to reroute through a traffic jam or what to do for dinner when you have no ingredients on hand
- Seeing information three dimensionally (visuospatial skills)
examples: making a mental map to walk around the neighborhood and back, judging distance between your car and the one in front of you while driving
No matter when and how significantly Parkinson’s affects cognition, it tends to impact attention and executive function more than memory.
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Mild Cognitive Impairment
Mild cognitive impairment (MCI) is a change in thinking or memory that is more than expected with normal aging but is not enough to interfere with a person’s daily activities. People with MCI may feel distracted or disorganized or lose their train of thought. They might find it more challenging to concentrate or manage multiple tasks at once.
As with all Parkinson’s symptoms, treatment of MCI is individualized. Doctors typically recommend that you keep your brain active and work with an occupational therapist, speech therapist or cognitive rehabilitation specialist to strengthen cognitive skills and manage your specific challenges. (Your physician can refer you to one of these experts.) Your doctor also will look for and treat any medical condition, such as a urinary tract infection, depression or sleep problem, which could potentially worsen cognition. (See: Testing.) At the current time, there are no U.S. Food and Drug Administration (FDA)-approved medications to treat mild cognitive impairment in Parkinson's, but research in this area is ongoing.
Estimates vary, but approximately 25 percent of people with Parkinson’s experience MCI. Mild cognitive impairment could stay the same, get better or worsen over time. In some people, MCI gradually progresses to dementia.
Dementia is a broad term for a change in thinking or memory that is significant enough to interfere with daily routines, work or social activities. If dementia occurs in Parkinson’s disease, it’s typically after many years or decades of living with disease.
People with Parkinson’s disease dementia (PDD) experience many of the same symptoms as those with mild cognitive impairment, but to a more considerable degree. Because they have problems with attention and executive function, they may have difficulty planning and completing activities and may take longer to process information and respond to questions. They may have trouble finding words, get lost in familiar places and be more easily confused.
Parkinson’s disease dementia shares symptoms and brain changes (alpha-synuclein protein clumps called Lewy bodies) with a related disease called dementia with Lewy bodies (DLB). These two diseases — PDD and DLB — are grouped under the umbrella term Lewy body dementia. Lewy body dementia causes thinking and memory changes (dementia) and movement symptoms (tremor, slowness, stiffness, and walking and balance problems). It also can lead to hallucinations (seeing things that aren’t there), delusions (false, often paranoid, beliefs), fluctuations in attention and alertness (being “with it” one day and “out of it” the next), and sleep, mood and behavioral changes.
Because of their similarities, doctors and researchers distinguish PDD and DLB primarily based on when movement symptoms and dementia arise. People with Parkinson’s disease dementia start with movement symptoms and many years, or decades, later develop dementia. In dementia with Lewy bodies, the movement symptoms and dementia begin at the same time or within a year of each other.
Not everyone with Parkinson’s experiences dementia. Estimates vary, but about 40 percent of people with Parkinson’s have PDD, and small studies suggest this number may be higher in people who have had Parkinson’s for 20 years or more. Certain factors may increase risk for dementia: a longer course of PD, significant movement problems (more walking and balance problems rather than tremor), mild cognitive impairment, seeing things that aren’t there (hallucinations) or believing things that aren’t true (delusions).
Medications can ease symptoms and improve quality of life, but none has yet been proven to slow or stop disease progression. Symptoms and their commonly used treatments include:
Thinking and memory changes
Treatments: Aricept (donepezil), Exelon (rivastigmine), Namenda (memantine), Razadyne (galantamine)
These medications were originally developed to treat Alzheimer’s disease. Aricept, Exelon and Razadyne boost the brain chemical acetylcholine, which supports memory and thinking; Namenda works on the glutamate brain chemical pathway. Exelon is the only one FDA-approved to treat PDD, but doctors often use the others “off label” in people with Lewy body dementia. These medications may temporarily boost cognition; lessen behavioral changes, such as agitation; decrease hallucinations and delay the need for alternative living situations, such as a long-term care facility.
Treatments: levodopa/carbidopa (Duopa, Parcopa, Rytary, Sinemet)
For stiffness, slowness and tremor, doctors may prescribe Parkinson’s medications, such as levodopa. Physicians aim to use the lowest effective dose to control symptoms without causing side effects, such as hallucinations or delusions. In people with Lewy body dementia, these medications may be more likely to cause or worsen hallucinations and delusions, so doctors use them cautiously. Physical and occupational therapy also may help, especially with walking, balance and fine motor issues (problems using utensils or tying shoelaces, for example).
Mood and behavior changes
Treatments: Celexa (citalopram), Prozac (fluoxetine), other anti-depressants and anti-anxiety medications
For mood or behavior changes, such as agitation or aggression, doctors may first recommend non-medication strategies, such as maintaining a soothing environment (avoiding loud television and violent or political programs, for example) and talking calmly to a loved one who is upset. If symptoms continue, your doctor may prescribe medication or recommend consultation with a psychiatrist. There are many different antidepressants and researchers have studied only a few specifically in Parkinson’s and dementia. When treating people with these conditions, doctors select carefully from the wide variety of drugs available, often using them “off label.” Anti-anxiety drugs also may be helpful, but many have potential side effects such as sleepiness or confusion, so they generally are used sparingly in dementia.
Hallucinations and delusions (psychosis)
Treatments: Clozaril (clozapine), Nuplazid (pimavanserin), Seroquel (quetiapine)
Doctors often avoid these medications in Lewy body dementia because of the potential for significant side effects, including increased risk of death in elderly people with dementia. But when hallucinations or delusions jeopardize a person’s (or their care partner’s) safety or well-being, doctors may prescribe them. As with any medication, you and your doctor must weigh the potential benefits (fewer or less severe hallucinations and delusions) against the possible side effects (sleepiness, confusion and potentially more significant effects). Nuplazid is FDA-approved to treat hallucinations and delusions in Parkinson’s, but doctors sometimes use it and the others “off label” in people with Lewy body dementia. Because many of these drugs (called atypical antipsychotics) block the brain chemical dopamine, they can worsen movement symptoms, so it’s important to use them cautiously.
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If you or your loved one notice thinking or memory changes, tell your doctor. Your physician may ask if you have other symptoms such as depression, anxiety, sleep problems or apathy (lack of motivation) — all common in Parkinson’s — which can impact cognition. Your doctor also may review your prescription and over-the-counter medications to ensure none are contributing to cognitive changes. Parkinson's medications such as trihexyphenidyl, for example, can sometimes cause confusion.
No brain imaging or blood tests can diagnose Parkinson’s cognitive changes. But doctors may order these to look for other conditions, such as low thyroid or vitamin B12, which can affect cognition. Your doctor likely will do basic memory tests (ask you to remember three objects, repeat a sentence, etc.) and in some cases may recommend neuropsychological testing for a more thorough and detailed examination.
Researchers are working out exactly why and how Parkinson’s causes thinking and memory problems. They believe both brain chemical and brain cells changes play a role. Parkinson’s affects several brain chemicals, including dopamine, acetylcholine, serotonin and norepinephrine, which are important for cognition. And in brain cells that are responsible for cognition, the protein alpha-synuclein misfolds and clumps into clusters called Lewy bodies, which researchers believe causes cell damage or death.
Researchers are working to understand how and why cognitive changes happen in Parkinson's, and to develop treatments for both mild cognitive impairment and dementia. Investigators are testing a variety of therapies for potential benefit: novel medications, brain and body exercises, and non-invasive brain stimulation. They also are looking for tools, such as rating scales, and measurements, such as brain scans, to better diagnose these conditions and distinguish different types of dementia (Alzheimer’s, Lewy body dementia, etc.). The Michael J. Fox Foundation supports work in this high-priority area, and is building inroads with regulators to ensure the right scales are created to properly evaluate therapies in development.