Study on identifying stroke in comatose patients — ScienceDaily


Subarachnoid hemorrhage is a form of bleeding stroke that can lead to a delayed ischemic stroke after just a few days. Researchers at Charité – Universitätsmedizin Berlin have shown that massive electrochemical waves in the brain serve as a marker that announces an imminent ischemic stroke. Electrodiagnostic monitoring of these waves allows physicians to identify the early signs of an impending stroke, particularly in comatose patients treated in the ICU after a subarachnoid hemorrhage. The researchers’ findings, published in Brain, could serve as a basis for developing new treatments.

Subarachnoid hemorrhage is a type of stroke caused by bleeding into the space between the protective membranes surrounding the brain. This type of hemorrhagic stroke is a neurological emergency and patients with this type of stroke require immediate critical care. When the normal blood supply to the brain is disrupted due to an acute blockage and not due to cerebral hemorrhage, it is called an ischemic stroke. However, an ischemic stroke can also occur as a result of a subarachnoid hemorrhage. More than half of all patients who have had a major subarachnoid hemorrhage will develop an ischemic stroke within the first two weeks after their cerebral hemorrhage.

Researchers at the Charité have identified a biomarker that indicates a patient’s high risk of an impending stroke after subarachnoid hemorrhage. “Especially in the case of patients who are in a coma and therefore cannot say anything about their state of health, it is difficult to assess when a new stroke will develop,” explains first author Prof. Dr. Jens Dreier from the Charité Center for Stroke Research. He continues: “We showed in our study that electrodiagnostic monitoring makes this moment visible. This means that treatment can be started in good time, even in comatose patients, before it is too late.”


The discovery by Prof. Dreier and his team was based on a phenomenon known as “propagating depolarizations,” massive waves of electrochemical energy release caused by the toxic byproducts of blood degradation after a hemorrhagic stroke. Affected areas of the brain require large amounts of energy to restore normal states. In a healthy brain, very short periods of depolarization (change in membrane potential) of nerve cells are normal and associated with the blood supply: the brain can dilate the blood vessels as needed and thus compensate for an increased energy requirement with increased blood flow. After a subarachnoid hemorrhage, however, pathologically massive and long-lasting spreading depolarizations can disrupt signaling cascades between nerve cells and blood vessels, such that the depolarization of nerve cells triggers extreme vasoconstriction. This, in turn, depletes nerve cells of energy, rendering them unable to restore normal electrochemical gradients. If the depolarization lasts too long, these nerve cells begin to die.

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“One scientific finding of the last few years was crucial: namely that the depolarization wave remains reversible up to a certain point in time,” emphasizes Prof. Dreier. He adds: “This means that the cells can fully recover if the blood flow and thus the oxygen supply are restored in time.”

This was the starting point of the current clinical study, which was carried out at five different university hospitals. To make accurate measurements of the propagating depolarizations, the researchers used electrocorticography, a technique used to measure brain activity in neurological intensive care patients. To enable these types of measurements, patients with a subarachnoid hemorrhage had electrodes implanted under the dura mater (the hard outer membrane of the brain). The researchers also used imaging techniques such as magnetic resonance imaging (MRI) and computed tomography (CT) and analyzed about 1,000 brain scans from 180 patients with subarachnoid hemorrhage. The largest clinical study on the propagation of depolarizations to date has shown that the average patient loses 46 milliliters of brain tissue in the early phase after his cerebral hemorrhage, ie before he arrives at the hospital. The average patient then loses another 36 milliliters of brain tissue in the first two weeks after his bleeding, i.e. in the intensive care unit.

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“These 36 milliliters of brain tissue can be practically used,” explains Prof. Dreier. He continues: “Electrodiagnostic monitoring allows us to detect developing strokes at a stage where the process can still be reversed and modified. Spreading depolarizations can therefore serve as biomarkers in real time. In a way, this replaces an exchange with the patient.” who are unable to express their symptoms and impairments due to their unconsciousness, enables us to initiate appropriate treatment measures at an early stage in patients who have been identified as being at risk of a new stroke and prevents those who are at risk of stroke If this is not the case, additional medication is given. There is a risk of another stroke. Possible side effects can be avoided in this way.”

This approach follows the principles of precision medicine, which aims to tailor treatments to the needs of the individual patient. The researchers plan to test spreading depolarization monitoring as an early warning system for use in routine clinical practice, where they hope it will help improve treatment options for people with stroke. Methods based on artificial intelligence are likely to play a major role in this. Automated analysis of electrodiagnostic data will be necessary to ensure that critical care physicians are notified in real time if an unconscious patient’s brain tissue is at risk of further damage.

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Materials provided by Charité – University Medicine Berlin. Note: Content can be edited for style and length.


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