Arterial connections improve stroke recovery

Arterial connections improve stroke recovery
Illustration of the blood vessels of a patient with slow re-perfusion of the brain after the removal of the blood clot in the blocked artery © P. Thurner and Z. Kulcsar, University Hospital Zurich

Blood vessels that connect neighboring arterial trees can prevent permanent brain damage from occurring after a stroke. They regulate blood circulation in the brain and therefore have a major influence on the successful regeneration of stroke patients.

Stroke is one of the most common causes of death in Germany – around 550 people suffer from it every day. In 80 percent of cases it is an ischemic stroke (cerebral infarction). In this case, parts of the brain are not supplied with enough blood because the arterial supply is blocked due to a blood clot. Calcified and thickened artery walls are often the cause. In order to restore blood flow to the brain, the blocked vessel must be opened. This most often happens through medicinal thrombolysis – the administration of active ingredients that dissolve the blood clot. But even if the blood clot can be removed in time, many affected patients have difficulty recovering.

Nadine Binder from the University of Zurich and her colleagues have gained new insights into recovery after a stroke. To study changes in arterial blood supply after the blood clot was removed, she conducted mouse experiments. The experimental animals differed in the expression of their collaterals. These are blood vessels in the brain that connect neighboring arterial trees.

The researchers were able to observe that mice that had a poor collateral network experienced poor regeneration after a stroke and the removal of the blood clot. “The subsequent excessive blood circulation led to bleeding and increased mortality in the mice,” explains senior author Susanne Wegener from the University of Zurich.

The team observed something similar in human stroke patients: those affected with few cross-connections in their cerebral arteries also showed too rapid and strong blood circulation in the brain after the blood clot was removed. Here too, small hemorrhages occurred in the affected area of ​​the brain and poorer recovery.

Hope for greater therapeutic success

The research team concludes that the success of stroke treatment depends on the collaterals in the brain. If there are a sufficiently large number of these vascular connections, the blood flow can be redirected via them in the event of a vascular blockage. Our image also shows this: The colored tracks show the arterial blood flow in the brain of a stroke patient after the blood clot has been removed. “These vascular bridges maintain the brain’s self-regulation and allow for slower, gradual re-perfusion, which leads to smaller infarctions,” says Wegener.

The problems caused by rapid blood circulation after stroke treatment have so far received little attention. Until now, the focus has been on removing the clot in order to restore the blood supply as quickly as possible. The new research results now give hope for greater therapeutic success through the new findings. Patients at risk could now be identified based on their artery network in the brain before the blood clot is removed. “Future therapeutic measures should aim to improve the function of the vascular bridges in order to enable favorable, gradual recirculation after the stroke,” explains Wegener.

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