Possibilities of collateral blood supply of brain

1. Big picture

Collateral blood supply means alternative vascular routes that can maintain cerebral perfusion when a main artery is stenosed or occluded. This is extremely important in cerebrovascular disease because the clinical severity of carotid or vertebrobasilar occlusion depends not only on the occluded artery, but also on how good the collateral circulation is.

A patient with slowly progressive internal carotid artery (ICA) stenosis may remain asymptomatic for a long time if collateral circulation is good. In contrast, a sudden embolic occlusion may cause a large infarct because there is no time for collateral adaptation.

For the exam, the main collateral routes are:

1. Circle of Willis

2. External carotid artery – internal carotid artery connections, especially via the ophthalmic artery

3. Leptomeningeal / pial cortical anastomoses between anterior cerebral artery (ACA), middle cerebral artery (MCA), and posterior cerebral artery (PCA) territories

4. Vertebrobasilar and cervical collateral routes

5. Anatomical variants, especially fetal PCA and persistent embryonic arteries, as exam traps