What Is Parkinson’s Disease Dementia?
Parkinson's disease (PD) is a movement disorder of the nervous system that gets worse over time. As nerve cells (neurons) in parts of the brain weaken, are damaged or die, people may begin to notice problems with movement, tremors, stiffness in the limbs or the trunk of the body, or impaired balance. As symptoms progress, people may have difficulty walking, talking or completing other simple tasks. Not everyone with one or more of these symptoms has PD, as the symptoms also appear in other diseases. A year after diagnosis, some people who are living with PD may also experience cognitive changes, such as a decline in their memory, reasoning skills or thinking. This decline in cognitive skills is known as Parkinson’s disease dementia (PDD).
Causes of Parkinson’s Disease Dementia
As with PD, the precise cause of PDD is unknown. Parkinson's disease occurs when nerve cells, or neurons, in the brain die or become impaired. Although many brain areas are affected, the most common symptoms result from the loss of neurons in an area near the base of the brain called the substantia nigra. The neurons in this area produce dopamine. Dopamine is the chemical messenger responsible for transmitting signals between the substantia nigra and the next “relay station” of the brain, the corpus striatum, to produce smooth, purposeful movement. Loss of dopamine results in impaired movement.
When there is a build-up of a specific protein in the brain called alpha-synuclein, they can form “Lewy bodies,” or clumps of protein in the nerve cells. These clumps cause otherwise healthy cells to stop functioning and eventually die. In the early stages of PD, Lewy bodies affect the part of the brain connected to movement and motor skills. Still, as the disease progresses, parts of the brain that control memory and thinking functions may also be impacted, leading to PDD.
Risk Factors for Parkinson’s Disease Dementia
Individuals with PD may experience mild changes in cognitive performance (MCI) roughly ten years after diagnosis. These symptoms may worsen over time and develop into PDD, though these changes vary from one person to the next. Risk factors for PDD include:
- Advanced age at the time of diagnosis
- A longer course of PD
- More severe motor symptoms
- PD patients with postural instability and gait disturbance (PIGD)
- Individuals who experience hallucinations
- Unusual daytime sleepiness
- A MCI diagnosis
Screening for & Preventing Parkinson’s Disease Dementia
There are currently no specific tests to diagnose Parkinson’s disease dementia, though cognitive changes will be monitored closely by doctors. Your medical team may also order blood tests to check for conditions such as low thyroid of vitamin B12, which are indicators of cognition impairment.
Signs & Symptoms of Parkinson’s Disease Dementia
Parkinson’s disease does not affect everyone the same way. The rate of progression and the particular symptoms differ among individuals. Typical symptoms of PD include problems with movement, tremors, stiffness in the limbs or the trunk of the body, or impaired balance. As the brain changes and symptoms progress, some may have difficulty walking, talking or completing other simple tasks. In the later stages of PD, cognitive problems may also develop and become more severe over time, leading to slow thinking and memory problems as well as impaired social judgment, language, reasoning, or other mental skills. These are signs of Parkinson’s disease dementia (PDD).
As with PD, those diagnosed with PDD will experience changes in symptoms over time. When signs of cognitive changes first appear, an individual may be diagnosed with mild cognitive impairment (MCI). For some, MCI symptoms stay the same over time and do not worsen, while other cases gradually progress to PDD.
Individuals with MCI may experience one or more of the following symptoms:
- Losing a train of thought
- Challenges with concentration
- Feeling disorganized
- Easily distracted
- Problems with managing more than one task at a time.
Those who do experience an impact on everyday activities, work and typical routines with significant cognitive decline and more extreme cases of the symptoms above are typically diagnosed with PDD. Symptoms of PDD include one or more of the following, which typically change and worsen as the disease progresses:
- Issues with executive function
- Trouble finding words, completing thoughts and sentences
- Get lost in otherwise familiar places
- Depression, anxiety or irritability
- Trouble focusing
- Sleep disturbances, such as daytime sleepiness and REM behavior disorder
- Hallucinations
- Changes in memory and judgment
- Muffled speech
- Paranoia and delusions
Diagnosing Parkinson’s Disease Dementia
Doctors will monitor all symptoms of PD, including cognitive impairment or changes in memory, focus, and executive function. After the onset of PD symptoms, they may begin noticing symptoms of MCI or PDD within a year and may run tests for low thyroid or vitamin B12 deficiencies, both of which can affect cognition.
Care teams may conduct memory tests to assess and monitor cognition, such as:
- The Mini-Mental State Examination (MMSE)—Recommended by the Movement Disorder Society, this 5- to 10-minute screening tool checks for signs of cognitive impairment by testing concentration, attention, orientation, naming skills, verbal memory and visuospatial skills.
- Episodic memory test (PAL)—This test assesses verbal and visual episodic memory and asks an examinee to remember a list of words, recall a story and copy a figure or drawing.
- Montreal Cognitive Assessment (MoCA)—Typically used for early detection of MCI, the MoCA screens for attention, concentration, memory, language, conceptual thinking, calculations, orientation, and executive function.
Doctors may also recommend neuropsychological testing, a more in-depth screening process lasting between two and eight hours. This comprehensive assessment typically involves pencil and paper tests and interviews and evaluates the following mental functions:
- Behavior
- Attention
- Learning
- Language
- Memory
- Processing Speed
- Reasoning
- Problem-Solving
- Reading
- Mood
Treating Parkinson’s Disease Dementia
There is no known cure for PDD. However, medicines such as cholinesterase inhibitors (rivastigmine, galantamine, and rivastigmine) can help with memory problems and may help patients manage some symptoms. While symptoms like hallucinations can be upsetting, they are harmless and usually pass quickly. Those struggling with sleep disorders may benefit from using melatonin or Clonazepam. Additionally, working with a speech therapist, occupational therapist, or cognitive rehabilitation specialist can help to strengthen cognitive skills. Additionally, some SSRIs used to treat depression may help with some symptoms of PDD.
The care team should review all medications to monitor any contraindications with already prescribed medicines for PD treatment.
Living with Parkinson’s Disease Dementia
Changes in cognitive abilities that come with PDD can be challenging to accept. Support groups can help people cope with the disease's emotional impact. These groups can also provide valuable information, advice and experience to help people with PDD, their families and their caregivers deal with a wide range of issues, including locating doctors familiar with the disease and coping with physical limitations. Individual or family counseling may also help people find ways to cope with PDD.
People with PDD may also benefit from being proactive and finding out as much as possible about the disease to alleviate the fear of the unknown and to take a proactive role in maintaining their health. Working with a speech therapist, occupational therapist, or cognitive rehabilitation specialist can help strengthen cognitive skills and help with the impact of mental changes on daily routines.
As with PD, PDD changes over time, sometimes staying the same, getting better or progressively worsening. Because PD is a slow, progressive disorder, it is not possible to predict what course the disease will take for each person, and those diagnosed with PDD will typically live an average of 5-7 years following diagnosis.