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Developmental and radiological anatomy of the superficial cerebral convexity vessels in the human fetus.

The superficial cerebral vessels on the convex side of the cerebral hemisphere were investigated using 40 brains of aborted human fetuses (ranging from 2 to 7 months of gestational age), injected with radiopaque material either through the arterial or venous system. These brains, particularly their vessels, were studied in detail through stepwise roentgenography in stereo-pairs, photography and careful dissections. Morphological changes of the superficial vessels of the cerebral convexity reflect the developmental alterations of the cerebral structures, particularly those of the opercula and cerebral sulci. Between the gestational ages of 3 and 4 months, the middle cerebral artery and its tributaries run radially on the sylvian fossa and over the convexity. Anastomoses among the peripheral branches of the anterior, middle and posterior cerebral arteries take place on the convex side of the hemisphere. At the ages of 3 and 4 months, the middle cerebral vein and its tributaries are well developed compared with the superior and inferior cerebral (or ascending and descending cortical) veins. The middle cerebral vein and its tributaries rapidly regress from the 5th to 7th month. The superior and inferior cerebral veins, on the other hand, develop rapidly during this period. Owing to the development of the opercula and resultant depression of the insula, after seven months of gestation the middle cerebral artery and its branches, begin to differentiate into the vallecular (related to the sylvian vallecula or fronto-temporal notch), insular (related to the insular cortex), opercular (related to the frontal, parietal and temporal opercula) and convexity segments (related to the convex side of the hemisphere). The anastomotic veins of Trolard and Labbé are also recognizable at this stage. The superficial sylvian vein in the process of formation may also be detected. The configuration of the cerebral vessels on the convex side of the hemisphere is also affected greatly by the development of the cerebral sulci. These cerebral vessels may run along, or dip into the sulci. Since the development of the superficial cerebral vessels is closely related to that of the cerebral mantle, these studies should be correlated to detail with those of developmental alterations of the intraparenchymal vessels (medullary arteries and veins). The latter investigation will be presented in a future communication.