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International Parkinson and Movement Disorder Society
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Cognitive Impairment and Behavioral Problems in Parkinson’s Disease

Essential Facts for Patients

What Types of Cognitive Problems Can Happen in Parkinson’s Disease?

Many people with Parkinson’s disease (PD) have good memory and thinking (cognition) and function normally. However, while forgetfulness may occur with normal aging more serious trouble with attention, thinking, and memory can occur as PD advances.

Common cognitive problems in PD include difficulty with:

  • Paying attention or concentrating
  • Planning events, like organizing a busy day
  • Following a complicated conversation or solving complex problems
  • Forming thoughts quickly
  • Remembering events or event details, although hints or clues often bring the memory back

When changes are small, without a serious effect on your daily life, this is called mild cognitive impairment. When changes are severe enough to affect day-to-day activities, this is called dementia.

Why Do Cognitive Problems Happen?

Changes in mental ability happen as PD starts to affect the parts of your brain that control attention, thinking, and memory. In most cases, this only happens later in the disease, or as people age, usually over age 65.

Hallucinations and Delusions

Many people with PD who have cognitive impairment can also have hallucinations or delusions. Hallucinations are when people, while awake, see or hear things that are not really there. In PD, hallucinations are mostly visual. They may include “seeing” animals or people that are not there. At first, most people recognize that hallucinations are not real. Later on, it may become harder to tell what is real and what is not. PD patients may also have illusions such as thinking a spot on the wall is an insect.

Delusions are false beliefs that are not based on reality or fact. Common delusions include thinking there are extra people living in the house, your spouse is cheating, or someone is stealing from you. This usually happens in more advanced PD.

Mild hallucinations that you easily recognize as hallucinations do not need treatment. It is important that your doctor checks that you do not have an infection, especially of the urinary tract, or you are not on a medication that can cause hallucinations and delusions. Hallucinations and delusions often can be treated by adjusting medications, like those for sleep or pain. If these problems continue despite these changes, your doctor may try reducing some of your PD medications. If that does not help, or it makes your movement worse, then your doctor may prescribe medication used to help cognition. In addition, clozapine or quetiapine may help hallucinations or delusions but may cause sleepiness as a side effect. Clozapine also requires regular blood testing.

What Can I Do for Cognitive Problems?

Cognitive function may be helped with proper exercise, diet, sleep and blood pressure control.

Talk to your doctor if problems with thinking, memory, or making decisions start to affect your daily routines. Your doctor may want to do cognitive tests. Review your medications as medications used to treat PD or other medical conditions sometimes make cognition worse. Using pill boxes and medication reminders may help.

If memory problems become severe then:

  • Discuss with your family and doctor plans for future living arrangements, including home care or a care facility.
  • Let a trusted caregiver have power of attorney, depending on local legal requirements. If you are no longer able, this person will have the right to speak for you, arrange your finances, pay your bills, and more. Without a power of attorney, these needs can quickly become complicated and expensive.
  • Be sure your estate and your will are current. You will not be able to change your will if you have severe attention, cognitive problems.

Are There Treatments?

Some medications can help and have been studied in PD patients with dementia. They include rivastigmine, donepezil, galantamine and memantine.

Some people who take these medications notice good improvement while others notice little change. Common side effects of these medications are nausea and diarrhea.


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