Cognitive impairment is a common non-motor symptom of Parkinson’s disease and causes significant disability to patients and burdens for caregivers. Similar to motor symptoms, the characteristics of cognitive impairment in Parkinson’s disease can be quite variable, both in terms of what cognitive domains are impaired and the timing of onset and rate of progression.

Description of cognitive impairment

Cognitive impairment in Parkinson’s disease is characterized by predominant executive function deficits, attention difficulties, visuospatial dysfunction, slowed thinking, difficulties in word-finding, and difficulties in learning and remembering information.

Many people with Parkinson’s disease feel distracted or disorganized, or have difficulty planning and carrying out tasks. It may be harder for patients to focus in situations that divide their attention, like a group conversation. When facing a task or situation on their own, Parkinson’s disease patients may feel overwhelmed by having to make choices. They also may have difficulty remembering information, or have trouble finding the right words when speaking. For some, these changes are merely annoying; for others they interfere with work or with managing household affairs.

Cognitive changes in patients can range from Parkinson’s disease mild cognitive impairment (PD-MCI) to Parkinson’s disease dementia (PDD). PD-MCI can be detected only by various means of comprehensive neuropsychological observations and normally does not affect the patients’ daily operations. PDD hits more than one area of cognition and is severe enough to impair social or working functions.

While approximately 50 percent of patients with Parkinson’s disease experiencing some form of cognitive impairment, not all individuals are diagnosed with dementia, which is only diagnosed when cognitive impairments occur in more than one area of cognition and are severe enough to impair social or work functioning.

Causes of cognitive impairment in Parkinson’s disease

One cause of cognitive changes in patients with Parkinson’s disease is a drop in the level of dopamine, the neurotransmitter that is involved in regulating movement as well as cognition, memory and learning, attention, and sleep. However, the cognitive changes associated with dopamine declines are typically mild and circumscribed.

Other brain changes also are likely involved in cognitive decline in Parkinson’s disease. Researchers believe that changes in two other chemical messengers, acetylcholine and norepinephrine, could be linked to memory and executive function loss in Parkinson’s disease.

Management of cognitive impairment

Patients who are experiencing cognitive changes are advised to discuss them with their physician, who may provide ways to help. Doctors usually refer patients with Parkinson’s disease to a psychiatrist, a neuropsychologist, or a speech or occupational therapist for further evaluation and assistance.

In face of cognitive changes associated with Parkinson’s disease, doctors may prescribe drugs such as rivastigmine, donepezil, and galantamine. Patients with attention difficulties that are related to daytime sleepiness may benefit from stimulants.

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