Abstract
The circle of Willis is a potential collateral circuit supplying the three cerebral arteries. If one of these arteries becomes occluded, preexisting anastomoses between their terminal branches or the arteriolar plexus between adjacent branches may enlarge, providing collateral circulation. Anastomoses between dural and cerebral arteries also may enlarge over the vertex. In occlusion of an internal carotid, extracranial vessels can resupply the cerebral cortex via the orbital plexus and ophthalmic artery. In slowly progressive bilateral internal carotid occlusions, a rete mirabile caroticum may develop and subsequently interconnect the ascending pharyngeal/internal maxillary and internal carotid arteries distal to the occlusion.
- © 1974 by the American Academy of Neurology
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