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Nuclear medicine for better diagnosis and therapy of Alzheimer's


Safe diagnosis and new therapeutic approaches in Alzheimer's thanks to nuclear medicine
Alzheimer's is the most common form of dementia and is relatively widespread, especially in older people. However, both the causes of the disease and the underlying mechanisms remain relatively unclear. The German Society for Nuclear Medicine reports that new nuclear medicine imaging methods could make a significant contribution here.

The neurodegenerative diseases will be a main topic at the joint annual meeting of the German, Austrian and Swiss societies for nuclear medicine in Dresden at the end of April. Because new nuclear medicine methods of molecular imaging can help "objectively record the changes in the brain and thus better understand the development of these diseases and hopefully treat them successfully in the next step," said the DGN communication.

Neurodegenerative diseases particularly feared
Dementia is a particularly feared complaint in view of the associated decline in intellectual ability and the loss of personality traits. They belong to the so-called neurodegenerative diseases such as Parkinson's disease, although Parkinson's is primarily expressed in neurodegenerative movement disorders, while dementia primarily affects cognitive abilities.

Difficulties in diagnosis and therapy
Both symptoms (Parkinson's and dementia) “are neurodegenerative diseases, more precisely those that lead to loss of function and failure of nerve cells,” explains the DGN. At the same time, these diseases are particularly difficult to diagnose and treat, which is partly due to the fact that the neurodegenerative diseases begin to spread in the brain many years to decades before the first symptoms that can be detected. Here, however, the brain is able to compensate for the failures to a certain extent through compensation mechanisms, and the process therefore goes unnoticed for a long time, explains the DGN. A diagnosis is often made accordingly late.

Record changes in the brain and better understand the causes of diseases
Even after the onset of the first symptoms, a reliable diagnosis of the cause of the disease often remains impossible "because its appearance varies and therefore does not allow any reliable conclusions to be drawn about the underlying changes in the brain", the DGN announcement. "New nuclear medicine methods of molecular imaging can now help to objectively record the changes in the brain and thus better understand the development of these diseases and hopefully treat them successfully in the next step," reports the specialist society.

Protein deposits in the brain are vital
Until now, reliable detection of pathological protein deposits in the brain was only possible by analyzing brain tissue under a microscope, so that a reliable diagnosis of the disease was not possible during the patient's lifetime, reports the DGN. Two forms of pathological protein deposits in the brain are typical for Alzheimer's: the so-called amyloid plaques in the intercellular space of the brain and further deposits of the so-called dew protein (neurofibrils or "tangles") in the nerve cells. The exact effect of the protein deposits has so far been not known, but it is assumed that they are causally related to the disease, according to the DGN.

Visualization of abnormalities in the brain
The DGN reports that the early forms of the glued protein fragments probably impair the function of the synapses - i.e. the nerve transmission points - and thus the nerve cells as a whole. With the help of new nuclear medical imaging methods, visualization of the relevant abnormalities in the brain is now also possible in living people. This is done using so-called positron emission tomography (PET). "In this highly sensitive imaging method, changes in molecular size are made visible in humans through the use of so-called tracers - low-radioactively labeled detection substances," the experts explain.

So-called tracers make the protein deposits visible
First, in preparation for PET, patients are injected with a small amount of the tracer substance in an arm vein so that it spreads throughout the body and then specifically connects to the pathological protein deposits in the brain, reports the DGN. The distribution of the tracer in the body can then be "represented by the radioactive radiation emitted by it using a special, highly sensitive PET camera." The procedure is not associated with any pain or other inconveniences for the person examined.

Basis for the development of new therapeutic approaches
In the meantime, numerous tracers have been developed for neurodegenerative diseases and, for example, they have been able to detect amyloid deposits in this way for some time, reports the DGN. Alzheimer's disease can thus be detected or excluded very early, the latter playing an important role especially in patients with slight impairments in their mental performance. Likewise, the amyloid imaging process is of great importance with regard to the development of new therapeutic approaches against Alzheimer's and their subsequent success monitoring. Only recently have tracers also become available, which enable imaging of dew deposits. However, the tau tracers are currently still being tested and have not yet been used routinely, according to the DGN. (fp)

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