2023-12-28 18:45:14
Stroke is a type of medical emergency that represents the second cause of death and the first cause of disability in adults worldwide, according to the World Health Organization (WHO). Every year, 15 million people suffer a stroke, of which five million die and 30% suffer permanent disability. When a person suffers a cerebrovascular accident (a stroke or a subarachnoid hemorrhage), electrochemical waves are generated that slowly travel through the tissue from the damaged area, killing neurons as they pass. In a period of a few hours, several of these waves will produce irreversible damage to a large volume of the cerebral cortex, which is why it is considered a critical window of time for medical personnel to try to save the tissue and reduce the consequences. irreversible neurological damage, or in a large number of cases, death. The maximum time to act and try to save the tissues is a few hours, a maximum of one day.
In the clinic, the extent of damaged brain volume is monitored in the patient using electrode strips placed on the brain surface. The area where the activity of the electroencephalogram is lost gradually spreads (in English, spreading depression) and is taken as an indication of the damaged brain volume, which helps medical personnel to know the evolution of the tissue and determine when and with what strategy to proceed. to try to protect it.
The authors of the new study have proven that cortical tissue that still shows EEG (brain encephalography) activity may, in fact, already be suffering from the irreversible death of the most superficial neuronal layers.
The study, carried out in parallel with patients and in animal models, has been carried out by an international team made up of, among others, Óscar Herreras, from the Cajal Institute of the Higher Council for Scientific Research (CSIC) in Spain, Azat Nasretdinov from the Federal University of Kazan in Russia, as well as researchers from Aix-Marseille University (R. Khazipov) and the Medical University of Berlin (J. Dreier).
Artistic recreation of dying brain cells in an area of the brain damaged by a stroke. (Illustration: Amazings/NCYT)
The team has developed a new biomathematical technique optimized in animals that allows precise monitoring of the evolution of brain damage in strokes. This methodology, tested in parallel in patients and in rodents, shows that brain tissue can present activity in an encephalogram due to electrical impulses from the deeper layers and, even so, be suffering irreparable damage in the more superficial ones. The results of the study advise, according to the authors, to rethink the criteria and perhaps the practice in the monitoring and treatment of cerebrovascular accidents.
The advance achieved in the new study has been possible thanks to the use of a complex biomathematical technique for analyzing brain electrical potentials that was previously optimized in animals in Madrid, and allows the activity of different neuronal layers to be separated and seen. The findings question the concept of the extent of EEG depression as a strict indicator of tissue that has died, since the superficial layers may have already succumbed and still present EEG that arrives from the deep layers. “The technique used is based on algorithms that allow processing mixed signals, that is, through multiple electrical recordings we can separate the activity of each neuronal population,” details Óscar Herreras.
The authors of the study believe that these findings make it advisable to rethink the criteria and perhaps the practice in the monitoring and treatment of strokes. “The amount of tissue that is taken as a criterion to evaluate the situation would be delayed by several hours, so they should look for another reference or some way to act sooner or faster,” concludes Herreras.
The study is titled “Diversity of cortical activity changes beyond depression during Spreading Depolarizations.” And it has been published in the academic journal Nature Communications. (Source: CSIC)
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