Parkinson Disease
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).
Parkinson Dementia
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.
Age
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.
Treatment
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.
Self-Care
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.
Medications
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.
Sources and
Additional Information:
