Johns Hopkins Health Alert
Unraveling the Mystery of Cognitive Impairment in Parkinsons Disease Patients
If you have Parkinson's disease, your body fails to produce enough dopamine, a substance necessary for smooth and coordinated movements. This loss of dopamine leads to the signature symptoms of Parkinson's disease: rhythmical shaking (tremor), stiffness, shuffling, slowness of movement, balance problems, small or cramped handwriting, loss of facial expression and soft, mumbled speech.
Although Parkinson's disease is a neurological disorder affecting movement, it is also associated with an often overlooked psychological condition known as cognitive impairment. Cognitive impairment can affect your memory and attention span as well as your ability to plan and organize. Many patients already have some degree of cognitive impairment when first diagnosed with Parkinson's disease.
As Parkinson's disease advances, the ability to recognize people and objects and communicate with others becomes increasingly difficult, especially in the later stages. Some experts believe that nearly all patients with Parkinson's disease will ultimately develop some degree of cognitive impairment.
The challenge of diagnosing cognitive impairment: Diagnosing cognitive impairment in Parkinson's disease patients is difficult because it’s often hard to tell whether certain symptoms are due to Parkinson's disease or another form of dementia. For instance, significant cognitive impairment could arise from Lewy body dementia rather than Alzheimer's or Parkinson's disease.
Lewy body dementia is associated with the abnormal accumulation in the brain of alpha-synuclein -- a protein whose function in healthy brains is still unknown. Alpha-synuclein is of great interest to researchers because it is a major constituent of Lewy bodies, the protein clumps that are a hallmark of Parkinson's. Scientists now believe that Lewy body dementia -- not Alzheimer's disease -- is responsible for most cases of dementia in Parkinson's disease patients.
Treating patients with Parkinson's disease when there are no signs of cognitive impairment is already a complex task. But treating patients with Parkinson's disease when evidence of cognitive impairment is present is even more complicated. Some medications commonly used to treat classic Parkinson's disease, such as levodopa, can worsen cognitive impairment and trigger bizarre behavior. Other drugs, such as antipsychotics (neuroleptics), can paradoxically increase hallucinations, delusions and agitation in Parkinson's disease patients who also have dementia.
Posted in Memory on November 28, 2011
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