Relevance of the cerebral collateral circulation in ischaemic stroke
This review paper from 4 years ago summarises very nicely the role of collateral flow in ischemic core progression. Since then further research has evaluated the predictive power of collateral score on patient outcome.
Relevance of the cerebral collateral circulation in ischaemic stroke: time is brain, but collaterals set the pace
Simon Jung, Roland Wiest, Jan Gralla, Richard McKinley, Heinrich P Mattle, David Liebeskind
Blood supply to the brain is secured by an extensive collateral circulation system, which can be divided into primary routes, i.e., the Circle of Willis, and secondary routes, e.g., collaterals from the external to the internal carotid artery and leptomeningeal collaterals. Collateral flow is the basis for acute stroke treatment, since neurones will only survive long enough to be rescued with reperfusion therapies if there is sufficient collateral flow. Poor collateral flow is associated with worse outcome and faster growth of larger infarcts in acute stroke treatment. Therapeutic promotion of collateral flow theoretically offers the chance for outcome improvement, but randomised trials are lacking. The extent of collateral flow is highly variable between individuals. As a consequence, the speeds of infarct growth are highly variable, resulting in varying individual treatment time windows until the whole salvageable tissue has become infarcted. An ideal patient selection for reperfusion therapies should be based on imaging of the salvageable tissue, the so called penumbra. The penumbra can be approximately visualised by computed tomography (CT) and magnetic resonance imaging (MRI), but both methods are significantly inaccurate in about 25% of the patients. There is a need for improved penumbra imaging by CT and MRI, and first studies applying machine learning techniques have shown promising results.
Read the full paper here:
Jung S, Wiest R, Gralla J, McKinley R, Mattle H, Liebeskind D. Relevance of the cerebral collateral circulation in ischaemic stroke: time is brain, but collaterals set the pace. Swiss Med Wkly. 2017;147:w14538. Published 2017 Dec 11. doi:10.4414/smw.2017.14538
There has always been a lot of research into treatment windows which is an important factor. But it is also important to remember that, at anytime, brain tissue is unlikely to survive long enough to undergo any reperfusion therapy unless the collateral flow can provide the tissue with oxygen.
Time is brain, but collaterals set the pace!