New research has shed light on why restoring blood flow after an ischaemic stroke does not always lead to neurological recovery. The study suggests that the brain’s own protective response can contribute to the formation of tiny blood clots in smaller vessels, potentially causing continued tissue damage even after the main clot has been removed.
Treatments such as thrombolysis and mechanical thrombectomy have transformed acute stroke care, but restoring blood flow does not always result in good neurological recovery. This phenomenon, known as ‘no reflow’, has remained poorly understood.
Researchers from the University of Colorado Boulder and the University of Antwerp used advanced microscopy to observe blood flow in the brains of mice during the period immediately following thrombectomy. Although blood flow returned after the original clot was removed, it was sometimes irregular, with flow changing direction or becoming intermittently disrupted.
Further investigation suggested that this abnormal flow contributed to the formation of micro-clots in smaller vessels. The researchers identified von Willebrand factor (VWF), a protein involved in blood clotting, as a potential driver of the process.
VWF normally helps prevent excessive bleeding by responding to damage within blood vessels. However, the researchers found that changes in blood flow following clot removal could cause VWF to unfold into thread-like structures capable of attracting platelets and promoting further clot formation.
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The inflammatory response to stroke may compound this effect by interfering with mechanisms that normally regulate VWF activity. Analysis of blood samples from people with stroke provided additional evidence that a similar process may occur in humans. Higher levels of the inflammatory molecule interleukin-6 were associated with increased VWF activity and poorer longer-term outcomes.
The findings raise the possibility that targeting VWF or the inflammatory pathways that enhance its activity could eventually complement existing reperfusion treatments. However, this remains an experimental approach, and further research is needed to establish whether targeting these pathways can improve recovery in patients.
Understanding why blood flow remains impaired after successful thrombectomy could ultimately help explain differences in recovery and identify additional therapeutic targets for improving outcomes after stroke.
This news item has been summarised using AI and checked by humans before publication.
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