23 May 2012

Brain tomography for the diagnosis of Alzheimer's disease

The US Food and Drug Administration (FDA) recently officially approved the use of a low-level radioactive label binding to amyloid plaques for the diagnosis of Alzheimer's disease.

Until now, doctors could only get confirmation of the presence of beta-amyloid aggregates in the patient's brain tissue after his death. However, this problem has already been solved: now clinicians can use a selectively amyloid-binding radioactive label, visualized using positron emission tomography. The FDA has approved the use of this method to assess the content of amyloid plaques in the brain tissue of patients suffering from cognitive impairment. Information about the presence or absence of plaques in the brain of patients complaining of forgetfulness, confusion or other signs of neurological problems will help attending physicians in determining the correct diagnosis.

The image shows aggregates of beta-amyloid in the brain tissue of a patient with Alzheimer's disease (bottom row), as well as their absence in the brain of a patient without cognitive impairment (top). The red end of the color scale corresponds to the maximum, and the black/blue end corresponds to the minimum concentration of the associated label.

Despite the absence of unambiguous evidence of a causal relationship between the presence of amyloid plaques in brain tissue and Alzheimer's disease, there is a pronounced correlation between the presence of these protein aggregates and dementia. Elderly people who have beta-amyloid aggregates in their brains have a more rapid decline in cognitive functions than people of the same age who do not have this symptom. To date, there are no effective methods of treating Alzheimer's disease, but diagnostic tools, such as amyloid plaque-binding tags, will allow doctors to differentiate patients with this disease and patients whose mental deterioration is due to other causes, for example, side effects of medications or depression.

A controversial point is the fact that amyloid plaques are often detected in the brain tissue of elderly people who do not suffer from deterioration of cognitive function, so today the diagnostic label is approved only as a means of excluding the diagnosis of Alzheimer's disease.

The new label, like other amyloid-binding dyes, has been used in clinical research for many years, but the manufacturer of the diagnostic agent Avid Radiopharmaceuticals, which is a subsidiary of Eli Lily, introduced this approach into practice for the first time. Some experts still consider this step premature, since if, based on the absence of plaques in the patient's brain, it can be said that amyloid is not to blame for the deterioration of his brain, then positive results of tomography can put the doctor at a dead end.

However, no one denies the importance of such an opportunity. With the help of the label, researchers will be able to identify patients with amyloid plaques in brain tissue, which will improve the planning of clinical trials of therapies aimed at destroying plaques. In the course of research, the use of the label will allow tracking the dynamics of changes in the number of amyloid aggregates in the brain tissue of patients in response to treatment.

Another promising application of the new label is the study of the causes and mechanisms of the development of the disease, knowledge of which is the key to the development of effective methods of its prevention and treatment. Researchers can monitor changes in the cognitive function of people with amyloid aggregates in the brain with the initial absence of neurological pathology. This will allow us to identify genetic and other factors that cause predisposition and resistance to the development of Alzheimer's disease.

Evgeniya Ryabtseva
Portal "Eternal youth" http://vechnayamolodost.ru based on the materials of Technology Review: Brain Scan for Alzheimer's.


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