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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.

Caring for patients with Parkinson's disease when there are no signs of cognitive impairment is already a complex task. But caring for Parkinson's patients 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 anti-psychotics (neuroleptics), can paradoxically increase hallucinations, delusions and agitation in Parkinson's disease patients who also have dementia.
 
Original article – Johns Hopkins Health Alert

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Lewy body dementia is a form of dementia that may account for as many as 20% of all dementia cases. Lewy bodies are tiny spherical deposits of a protein called alpha-synuclein that are found in the brains of patients with this disorder. The presence of Lewy bodies throughout the brain disrupts the brain's normal functioning. Lewy body dementia is now believed to be the second most common specific cause of dementia after Alzheimer's disease.

There is considerable overlap between Lewy body dementia and Alzheimer's and Parkinson's disease. In Lewy body dementia, patients experience a loss of dopamine-producing nerve cells similar to that seen in Parkinson's disease. They also lose acetylcholine-producing nerve cells, similar to what occurs in Alzheimer's disease.

Patients with Lewy body dementia often experience cognitive problems associated with Alzheimer's disease, such as memory loss, spatial impairment and language difficulties. They may also develop parkinsonian symptoms, such as muscle rigidity, a blank facial expression, soft voice, tremor, poor balance and gait disturbances. Some patients initially diagnosed with Parkinson's disease later go on to develop a dementia that closely resembles Lewy body dementia.

Certain symptoms of Lewy body dementia help distinguish it however. For example, early in the illness Lewy body dementia patients often experience detailed and extremely vivid hallucinations, unlike people with Alzheimer's disease. People with Lewy body dementia also tend to show marked fluctuations in their cognitive functioning, often several times a day. In addition, they tend to fall asleep easily during the day and have restless, disturbed sleep with behavioral acting out.

Recognition of these symptoms leads to an accurate diagnosis of Lewy body dementia. A correct diagnosis is particularly important because the medical management of patients with Lewy body dementia presents special challenges. The drugs that are normally used can aggravate other problems and cause potentially serious adverse reactions. In particular, antipsychotic drugs can provoke dangerous side effects, including a return to psychosis, and must be used cautiously, if at all. In addition, levodopa, a drug normally used to treat parkinsonian symptoms, may worsen hallucinations, so its dosage needs to be carefully adjusted in patients with Lewy body dementia.

This disease is named for Frederick Lewy, the physician who first identified them in 1912 while working in the laboratory of Dr. Alois Alzheimer.

Original article from Johns Hopkins

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