Sensory illusions and mental and physical impairments
Lewy body dementia usually occurs after the age of 65. To date, it is not really clear whether Lewy body dementia is a disease in its own right or a variant of Parkinson's with early onset dementia: Individuals with Lewy body dementia sometimes have symptoms similar to those of Alzheimer's and Parkinson's patients. Mixed forms of these three diseases are also known. Men are probably more likely than women to be affected by Lewy body dementia.
Typical signs: optical hallucinations
People with Lewy body dementia often have similar symptoms to Alzheimer's and Parkinson's patients: Thus, on the one hand, they suffer from progressive memory impairment and slowed thinking, with cognitive performance often fluctuating significantly throughout the day. On the other hand, movement disorders resembling Parkinson's disease occur. These include tremors, muscle stiffness, and slowed movements. In some persons, the body leans to one side of the body while walking or standing (Pisa syndrome).
As a special feature of Lewy body dementia, visual hallucinations occur very early in the course of the disease. These are often very detailed. Affected people see people or large animals, for example, which can trigger fear. Auditory hallucinations are less common. People with Lewy body dementia are often hypersensitive to neuroleptics, drugs that counteract such sensory illusions. As a result, movement disorders may increase, consciousness may become cloudy, or the affected person may fall into a deep sleep that lasts for days. Early on in Lewy body dementia, urinary incontinence and falls due to low blood pressure when standing up are also common.
Another typical symptom is disturbed REM sleep (dream sleep). Those who are affected really do live out their dreams, which is noticeable through restless sleep, increased movements, and talking in their sleep. This symptom also occurs in the early stages of Parkinson's disease, making diagnosis difficult.
Protein deposits in the neurons
Lewy body dementia is characterized by typical round inclusion bodies – called Lewy bodies – in the neurons of the cerebral cortex. These are deposits of a protein called alpha-synuclein, which is not broken down properly: Alpha-synuclein molecules stick together and form insoluble aggregates. Such protein deposits are also found to some extent in Parkinson's patients, but in a different area of the brain. Lewy body containing neurons degenerate and inhibit the messenger substance (neurotransmitter) dopamine, which is important for brain and muscle functions and transmits signals from one nerve cell to the next.
The actual cause of Lewy body deposits is not yet known. In some patients, the disease is associated with changes in the genetic makeup. These are genes that can also be altered in people with Parkinson's disease.
Tracking down the causes
Researchers at the DZNE are searching, among other things, for the biological mechanisms that underlie Lewy body dementia. For example, they are investigating how the abnormal protein deposits occur and why some neurons have a special tendency to take up, transport, and accumulate the protein molecule alpha-synuclein.
By comparing Lewy body dementia and Parkinson's disease, scientists at the DZNE hope to achieve a more precise diagnosis of both diseases in the future – and thus more a targeted therapy.
Discoverer of Lewy bodies
The neurologist, psychiatrist and neuropathologist Friedrich Jacob Heinrich Lewy was born in Berlin in 1885. After graduating from high school, he studied medicine in Zurich and Berlin. One of the laboratories Lewy worked in was headed by Alois Alzheimer, whom he followed to Breslau in 1912. Later he worked at the Charité in Berlin, where he acquired his post-doctoral degree in the field of neurology. Lewy first became head of the neurological department of the Charité in 1926 and head of the neurological institute in Berlin in 1930. In 1932, he founded an independent neurological clinic and research institute. However, he was only able to lead it until 1933, when the National Socialists revoked his teaching license because of his Jewish background. Lewy emigrated first to England, then later to the United States, where he changed his name to Frederic Henry Lewey.
Lewy became known as the discoverer of the Lewy corpuscles named after him, which he first described in Parkinson's patients in 1912. He had discovered the characteristic round protein deposits in certain neurons of the brain stem of deceased patients. It was not until 1989 that it became clear that Lewy bodies also occur in dementia patients who never show Parkinson's symptoms, or only at a late stage, in neurons of the cerebral cortex. This made it possible to distinguish Lewy body dementia as a disease in its own right.
Status as of 22.11.2021