Human telencephalic angiogenesis.

We provide new observations regarding the histogenesis and regional development of the human telencephalic microvasculature during the last half of gestation. Endothelium-lined trunks extending from pia to the subventricular plexus, evident early in gestation, persist during the last half of gestation. The courses of these trunks are modified and become complex as the bulk of the telencephalon, striatum, and thalamus increases and as gyri grow. New cerebral tissue is supplied by increasing numbers of shorter penetrating vessels. All extrastriatal vessels have many lateral right- and acute-angle branches that join nearby trunks and shorter vessels. Striatal vessel branches predominantly have acute angles. Most extrastriatal channels remain devoid of apparent muscularis until the final weeks of gestation. In contrast, striatal arteries begin to muscularize at about 24 weeks of gestation. Muscularization appears to occur in a centripetal direction and is apparent in the caudate at approximately 30 weeks' gestation. We did not identify transventricular, paraventricular, or recurrent arteries ending in deep white matter.