Parkinson’s disease dementia (PDD) refers to a condition in which a person who has been living with Parkinson’s disease (PD) – a neurodegenerative movement disorder – develops significant problems with thinking, memory and reasoning that interfere with daily life.
In PD, the earliest symptoms are typically movement-based (such as tremor, stiffness, slowness). Over time, in some (but not all) people, the disease process spreads so that cognitive changes emerge and worsen. When these changes become sufficient to constitute dementia, this is PDD.
While timing varies, research suggests that up to about 50% or more of people who have lived with Parkinson’s for more than 15 years will develop dementia.
What causes Parkinson’s disease dementia
In Parkinson’s disease dementia, the underlying brain changes include accumulation of abnormal protein deposits known as Lewy bodies (which are mainly composed of the protein alpha-synuclein) in nerve cells. These Lewy bodies impair normal cell function and contribute to neuron death. These changes typically begin in the brain stem, mainly brain regions responsible for movement, and then gradually progress into areas that control thinking and memory.
Risk of dementia in PD increases with certain features: for example, older age at onset, longer duration of PD, more prominent problems with balance and gait, and more severe motor features.
It is important to note that, like many neurodegenerative disorders, researchers do not fully understand the cause of the condition. It is not believed to be an inherited condition.
Common symptoms
Because PDD occurs alongside a movement disorder, common symptoms typically include both movement and cognitive changes. Movement symptoms (from underlying PD) include:
- Tremor (usually at rest)
- Muscle stiffness
- Slowed movement (bradykinesia)
- Shuffling gait
- Stooped posture
- Difficulty initiating movement
- Problems with balance and falls
Cognitive symptoms may include:
- Problems with attention, planning, multi-tasking
- Slowed thinking
- Difficulties with remembering information
- Hallucinations or visual misperceptions
- Apathy, mood disturbances (depression, anxiety), and fluctuating alertness
Cognitive symptoms typically emerge many years after the first motor signs of PD. Once dementia develops, the pace and pattern can vary.
How PDD is diagnosed and treated
Diagnosing PDD involves multiple steps. A neurologist will review the history of movement symptoms, timing of cognitive changes, and perform a neurological and cognitive assessment. A neuropsychologist will do cognitive testing to understand the pattern and severity of impairment. Imaging studies (such as an MRI) may also be used. Overall, a diagnosis of PDD is supported when dementia develops in a person with established PD, after motor symptoms have been present for at least 1 year.
While there is no cure for PDD, many interventions help manage symptoms and improve quality of life. These treatments may include:
- Medications, such as certain cholinesterase inhibitors and selective serotonin reuptake inhibitors (SSRIs)
- Physical therapy, occupational therapy and speech therapy to help with motor issues, gait and balance, and communication
- Cognitive behavioral therapy, also known as talk therapy, may be used to manage behavioral symptoms of dementia
Given the progressive nature of the condition, discussing advance care planning, legal and financial matters, and ensuring access to support services are important steps to take alongside medical care.
Support for families and caregivers
Caring for someone with PDD involves navigating both movement and cognitive challenges. A multidisciplinary approach improves outcomes for both the person with PDD and their care partner. Some key considerations for families include:
- Creating a safe home environment can help with mobility issues and reduce risk of falls and confusion
- Creating consistent routines, simplified tasks, visual and aural cues, and supportive communication strategies for the person living with the condition
- Addressing behavioral and mood changes early on
If you or a loved one has Parkinson’s disease and you’re noticing new difficulties with thinking, memory, or behavior, consider speaking with a dementia-experienced healthcare professional about the possibility of Parkinson’s disease dementia. Early, coordinated care can make a significant difference in quality of life.