Parkinson's disease (PD) is an age-related degenerative disorder of certain brain cells. It mainly affects movements of the body, but other problems, including dementia, may occur. It is not considered a hereditary disease, although a genetic link has been identified in a small number of families.
The most common symptoms of Parkinson's disease are tremor (shaking or trembling) of the hands, arms, jaw, and face; rigidity (stiffness) of the trunk and limbs; slowness of movement; and loss of balance and coordination.
Other symptoms include shuffling, speaking difficulties, (or speaking very softly), facial masking (expressionless, mask-like face), swallowing problems, and stooped posture.
The symptoms worsen gradually over years.
Depression, anxiety, personality and behavior changes, sleep disturbances, and sexual problems are commonly associated with Parkinson's disease. In many cases, Parkinson's disease does not affect a person's ability to think, reason, learn, or remember (cognitive processes).
About 1 in 5 people with Parkinson's disease develop dementia due to Lewy bodies in the brain and brain stem. The onset of Parkinson's disease itself involves damage to nerve cells that control muscle movement.
If Parkinson's disease patients experience hallucinations and have severe motor control, they are at higher risk for dementia. The development of dementia is slow. Typically, people that develop symptoms of dementia do so about 10 to 15 years after the initial diagnosis of Parkinson's disease.
Researchers use various definitions of cognitive impairment and dementia. Parkinson's disease often overlaps with other degenerative brain disorders that can cause dementia, such as Alzheimer's disease and vascular disease within the brain. Some researchers suggest that at least 50% of people with Parkinson's disease have some mild cognitive impairment and estimate that as many as 20% to 40% may have more severe symptoms or dementia.
Most people have the first symptoms of Parkinson's disease after the age of 60 years, but Parkinson's disease also affects younger people. Early-onset Parkinson's disease strikes people around the age of 40 years, or even earlier.
Regardless of age at onset of the disease, dementia symptoms tend to appear later (after about 10 to 15 years) in the course of the disease.
Dementia is relatively rare in people with onset of Parkinson's disease before age 50 years, even when the disease is of long duration.
Dementia is more common in people with an older age (about 70 years) at onset of Parkinson's disease.
Causes and Risk Factors for Parkinson's Disease Dementia
The causes of Parkinson's disease currently remain unclear; although about 10% are genetically linked, the remainder (approximately 90%), are of unknown cause. However, what is known is that clear evidence shows neuronal cells in an area of the brain known as the substantia nigra are altered and destroyed over time. The current popular theory is that combinations of environmental and genetic factors are responsible for this neuronal cell alteration and destruction. The result of these interactions results in the loss of dopamine production, loss of neurons that make dopamine, loss of other neuron-generated substances, and the presence of Lewy bodies in brain cells, all of which are found at autopsy of Parkinson's disease patients.
The major components thought responsible for these changes are not clearly defined but include exposures to toxic environmental substances, oxidation of free radicals that damage cells and their components (for example, generation of Lewy bodies from alpha-synuclein, a protein involved in neurotransmission) and mitochondrial dysfunction. People with certain gene combinations may be more likely to develop these alterations and have Parkinson's disease as a result.
Risk factors for dementia in patients with Parkinson's disease are as follows:
ü Age 70 years or older
ü Score greater than 25 on the Parkinson's disease rating scale (PDRS): This is a test that doctors use to check for progression of the disease.
ü Depression, agitation, disorientation, or psychotic behavior when treated with the Parkinson's disease drug levodopa (Sinamet, Sinemet CR, Parcopa)
ü Exposure to severe psychological stress
ü Cardiovascular disease
ü Low socioeconomic status
ü Low education level
Additional risk factors may include:
ü Hallucinations in a person who doesn't yet have other dementia symptoms
ü Excessive daytime sleepiness
ü Parkinson's symptom pattern known as postural instability and gait disturbance (PIGD), which includes "freezing" in mid-step, difficulty initiating movement, shuffling, problems with balance and falling.
Symptoms of Parkinson's Disease Dementia
Cognitive impairment in Parkinson's disease may range from a single isolated symptom to severe dementia.
ü The appearance of a single cognitive symptom does not mean that dementia will develop.
ü Cognitive symptoms in Parkinson's disease usually appear years after physical symptoms are noted.
ü Cognitive symptoms early in the disease suggest dementia with Parkinsonian features, a somewhat different condition.
Cognitive symptoms in Parkinson's disease include the following:
ü Loss of decision-making ability
ü Inflexibility in adapting to changes
ü Disorientation in familiar surroundings
ü Problems learning new material
ü Difficulty concentrating
ü Loss of short- and long-term memory
ü Difficulty putting a sequence of events in correct order
ü Problems using complex language and comprehending others' complex language
Persons with Parkinson's disease, with or without dementia, may often respond slowly to questions and requests. They may become dependent, fearful, indecisive, and passive. As the disease progresses, many people with Parkinson's disease may become increasingly dependent on spouses or caregivers.
Major mental disorders are common in Parkinson's disease. Two or more of these may appear together in the same person.
ü Depression: Sadness, tearfulness, lethargy, withdrawal, loss of interest in activities once enjoyed, insomnia or sleeping too much, weight gain or loss
ü Anxiety: Excessive worry or fear that disrupts everyday activities or relationships; physical signs such as restlessness or extreme fatigue, muscle tension, sleeping problems
ü Psychosis: Inability to think realistically; symptoms such as hallucinations, delusions (false beliefs not shared by others), paranoia (suspicious and feeling controlled by others), and problems with thinking clearly; if severe, behavior may be seriously disrupted; if milder, behavior that is bizarre, strange, or suspicious may occur.
The combination of depression, dementia, and Parkinson's disease usually means a faster cognitive decline and more severe disability. Hallucinations, delusions, agitation, and manic states can occur as adverse effects of drug treatment of Parkinson's disease, this might complicate the diagnosis of Parkinson's dementia.
How the symptoms compare to Alzheimer's? The symptoms of Parkinson's are usually diagnosed first because the dementia develops in the disease's later stages. Parkinson's dementia does not typically involve problems with language.
How Is Parkinson's Disease Dementia Diagnosed?
There is no definitive medical test that confirms cognitive decline or dementia in Parkinson's disease. The most accurate way to measure cognitive decline is through neuropsychological testing.
ü The testing involves answering questions and performing tasks that have been carefully designed for this purpose. It is carried out by a specialist in this kind of testing.
ü Neuropsychological testing addresses the individual's appearance, mood, anxiety level, and experience of delusions or hallucinations.
ü It assesses cognitive abilities such as memory, attention, orientation to time and place, use of language, and abilities to carry out various tasks and follow instructions.
ü Reasoning, abstract thinking, and problem solving are tested.
ü Neuropsychological testing gives a more accurate diagnosis of the problems and thus can help in treatment planning.
ü The tests are repeated periodically to see how well treatment is working and check for new problems.
Imaging studies: Generally, brain scans such as CT scan and MRI are of little use in diagnosing dementia in people with Parkinson's disease. Positron emission tomographic (PET) scan may help distinguish dementia from depression and similar conditions in Parkinson's disease.
There is no cure for dementia in Parkinson's disease. Rather, the focus is on treating specific symptoms such as depression, anxiety, and psychotic behavior. A specialist in these disorders (psychiatrist) may be consulted for treatment recommendations.
Protein in the diet may affect the absorption of levodopa, the major medication used to treat Parkinson's disease. Fluctuations in the level of levodopa may worsen some behavioral and cognitive symptoms. A low-protein diet may reduce fluctuations in dopamine levels. In some patients with these fluctuations, dietary changes can improve symptoms. However, it is important to ensure that the person is getting adequate calories and other nutrients.
People with Parkinson's disease should remain as active as possible. Physical therapy helps the person maintain mobility.
In general, people with Parkinson's disease plus dementia should no longer drive vehicles. Movement problems may prevent quick reactions in hazardous driving situations. Certain medications, especially those given to treat symptoms of dementia, may make them less alert. However, this should be determined on an individual basis and in compliance with the laws of the state.
Various medications are used to treat the movement disorders of Parkinson's disease; some may exacerbate symptoms related to dementia.
ü These include dopamine given in the form of levodopa; medications known as dopamine agonists (for example, a combination of carbidopa and levodopa known as Sinemet) that act on the dopamine receptor; and medications that slow down the metabolism of dopamine. They are often used in conjunction with monoamine oxidase inhibitors (MAO B,) such as rasagiline. In addition, anticholinergic drugs are sometimes used.
ü Unfortunately, these drugs may affect cognitive symptoms and mood disorders.
ü The anticholinergic drugs, for example, help balance levels of dopamine and acetylcholine, another neurotransmitter, in the brain. These drugs can improve movement disorders but often make memory loss worse.
The dementia of Parkinson's disease may respond to drugs used in patients with Alzheimer's disease. However, these drugs, called cholinesterase inhibitors (such as donepezil [Aricept], rivastigmine [Exelon], galantamine [Reminyl]), lead to only small and temporary improvements in cognition.
Mood disorders and psychoses are usually treated with other medication(s).
ü For depression and mood disorders, various antidepressant or mood-stabilizing medications, such as tricyclic agents (such as nortriptyline [Pamelor] or desipramine [Norpramin]) or selective serotonin reuptake inhibitors (SSRIs, such as fluoxetine [Paxil] or citalopram [Celexa]) are used.
ü For agitation or psychotic symptoms, atypical antipsychotics are preferred. Clozapine (Clozaril) is often the first choice, but it may have intolerable adverse effects. Quetiapine (Seroquel) may be an alternative. Olanzapine (Zyprexa) and risperidone (Risperdal) tend to worsen motor function.
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