Normal and Abnormal Embryology and Development of the Intracranial Vascular System
Section snippets
The primitive perineural vascular meshwork
Shortly after its closure (week 4), the neural tube becomes embedded in a solid mesenchyme that forms the meninx primitiva (see Fig. 2). This meninx primitiva of the forebrain (anterior neural plate) derives from the neural crest of the more caudal posterior diencephalic and mesencephalic segments.2, 11 The meninx primitiva of the developing spinal cord, hindbrain, midbrain, and posterior diencephalon derives from the somitic mesoderm.2
Vasculogenesis produces the vascular organ system and the
Morphogenesis of the brain arteries
Padget7 studied the development of the cerebral arteries by using a method of graphic reconstruction from 22 sectioned embryos of the Carnegie Collection ranging in age from 24 to 52 days (4–43 mm). Her outstanding contribution therefore rests on a relatively limited number of specimens. Based on the evolution of the cardiovascular system, especially the aortic and pulmonary arches, Padget identified, defined, and illustrated 7 steps or stages in the development of the brain arteries, from an
Angiogenesis: the intrinsic vascularity of the brain
The 2 main steps in the development of the forebrain (using it as a model of the whole brain) are firstly the cellular proliferation (in the germinal matrices or neuroepithelia) and migration, and then the energy-avid intracortical organization. Cellular proliferation and migration mainly occur before week 20, while cerebral connectivity becomes significant in the last trimester of gestation until well after birth. Accordingly, the brain vasculature develops in 2 separate episodes: the first,
Morphogenesis of the brain venous system
Unlike the arterial supply (from the periphery to the ventricle), there is dual venous drainage of the brain: the deep white matter veins drain into the subependymal venous system toward the vein of Galen, while the cortex and superficial white matter veins drain into the superficial, meningeal venous system. As for the arteries, the shaping of the venous system follows chronologically the development of the brain metabolism.
Before the intrinsic vasculature develops, the venous drainage is
Persistent Vestigial Carotid-Vertebrobasilar Anastomoses
These are occasional angiographic findings, identified as the persistent trigeminal, otic, hypoglossal, and pro-atlantal arteries, felt to reflect the homonymous embryonal (rather than fetal) arterial supply to the hindbrain (see Fig. 3, Fig. 16). It should be remembered that this embryonal (not fetal) pattern concerns tiny capillaries, lasts a few days only, and was identified in a very small number of specimens. This is likely the oldest brain vascular abnormality that can be clinically
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