Diagrams of persistent carotid-vertebrobasilar anastomoses from cephalic to caudal; persistent trigeminal artery, persistent otic artery, persistent hypoglossal artery, and persistent proatlantal artery (type I and II).
Case Discussion
In early embryological development the posterior circulation develops later than the anterior circulation 1. At 4mm the first two aortic arches have regressed, and the third arch and cephalic end of the dorsal aorta begin to form the internal carotid artery to supply the forebrain 2. During this early stage, the hindbrain's blood supply is reliant on the anterior circulation via a series of anastomoses 3. These vessels form between the developing internal carotid artery and the longitudinal neural arteries (precursors to the basilar artery) to supply blood to the hindbrain 1,2. These primitive anastomoses are as follows:
otic artery (persistence disputed)
As the posterior fossa and vertebral arteries develop these primitive vessels usually regress, leading to a typical postnatal configuration with the only communication between the anterior and posterior circulation being the posterior communicating arteries 1,3. When these vessels fail to regress, they appear as depicted in the above diagrams as persistent anatomical variants.
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