A Functional Perspective on the Embryology and Anatomy of the Cerebral Blood Supply

Abstract

The anatomy of the arterial system supplying blood to the brain can influence the development of arterial disease such as aneurysms, dolichoectasia and atherosclerosis. As the arteries supplying blood to the brain develop during embryogenesis, variation in their anatomy may occur and this variation may influence the development of arterial disease. Angiogenesis, which occurs mainly by sprouting of parent arteries, is the first stage at which variations can occur. At day 24 of embryological life, the internal carotid artery is the first artery to form and it provides all the blood required by the primitive brain. As the occipital region, brain stem and cerebellum enlarge; the internal carotid supply becomes insufficient, triggering the development of the posterior circulation. At this stage, the posterior circulation consists of a primitive mesh of arterial networks that originate from projection of penetrators from the distal carotid artery and more proximally from carotid-vertebrobasilar anastomoses. These anastomoses regress when the basilar artery and the vertebral arteries become independent from the internal carotid artery, but their persistence is not uncommon in adults (e.g., persistent trigeminal artery). Other common remnants of embryological development include fenestration or duplication (most commonly of the basilar artery), hypoplasia (typically of the posterior communicating artery) or agenesis (typically of the anterior communicating artery). Learning more about the hemodynamic consequence that these variants may have on the brain territories they supply may help understand better the underlying physiopathology of cerebral arterial remodeling and stroke in patients with these variants.

The Configuration and Variations in the Developing Circle of Willis – A Retrospective Autopsy Study

“…In 2 specimens (4.4%), the two ACAs join to form a single, median ACA (azygous ACA) which later on splits into two ACA. De Vriese, (1905) 13 and Menshawi, (2015) 2 has also confirmed the presence of single median ACA in fetus as observed in the present study. According to them this vessel is present normally in primates.…”

“…As the cerebral vascular tree reaches its typical configuration, the multiple events that occur during the embryological stage might lead to a diverse spectrum of vascular anatomical variants 1 . Duplications and fenestrations of an artery can occur due to an incomplete fusion of arteries 2 . This has been associated with the development of cerebral saccular aneurysm 5 .The theory behind the fact is that smooth muscle cells and collagen are decreased at the proximal and distal end of the fenestrated segment.…”

Unpaired Anterior Cerebral Artery Associated with Double Origin of Vertebral Artery: Case Report and Genetic Consideration

“…The paired cranial and caudal carotid branches feed the developing cerebral vesicles through the whole prechoroidal and choroidal stages (3-5 weeks), and the primitive anterior circulation remains dominant over the forming vertebrobasilar system until the beginning of the 8-9-week embryological stage 15 . The phylogenetically oldest cranial branch becomes the supply for the primary forebrain in the human embryo, representing the future ACA.…”

Agenesis of the internal carotid artery: a family pathology?

“…The embryology of the internal carotid artery is very complex (3) and this leads to the possibility of malformation disorders during its development. Lie described six anatomical variants in his classification (4) and in some cases the presence of aneurysms along the course of the primary vessel exacerbates the complexity of the disease (5).…”