Cerebral Veins
The embryological evolution of the venous system of the brain has been treated largely by many authors (Streeter 1918; Hochstetter 1938; Padget 1956, 1957; Kaplan and Ford 1966; Okudera et al. 1984; Raybaud et al. 1989). We summarize the essential points.
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Cerebral Veins
The embryological evolution of the venous system of the brain has been treated largely by many authors (Streeter 1918; Hochstetter 1938; Padget 1956, 1957; Kaplan and Ford 1966; Okudera et al. 1984; Raybaud et al. 1989). We summarize the essential points. The veins develop in a later stage in comparison to the arteries. In the early stages of the embryogenesis the venous drainage is characterized by a superficial network draining into a superficial dural plexus, formed by an anterior, middle and posterior parts, on either side, which drains into the paired Primary Head Sinus (PHS) continuing posteriorly in the Anterior Cardinal Veins (future Internal Jugular Veins). From the anterior part of the plexus, arises the Primitive Marginal Sinus which continues caudo-ventrally, in the Primitive Tentorial Sinus. Later, the PHS regresses, with exception of its anterior part, from which develops the cavernous sinus. The anterior middle and posterior components of the Dural Plexus fuse together on the midline, forming the Superior Sagittal Sinus, continuing in the Torcular Herophili and further in the now formed Transverse - Sigmoid sinuses. From these dural complex arises progressively the superficial venous system, including the cortical veins collecting the blood from the pial and medullary veins. The deep venous system appears later. It is characterized by choroidal, diencephalic veins and by a large median venous channel known as the median prosencephalic vein (PV) (Markowski 1922) or as primitive internal cerebral vein (Padget 1956, 1957). These veins drain the blood of the well-developed choroid plexus
into the Primitive Marginal Sinus directly or through a primitive straight sinus. The development of the basal ganglia and thalamus results in the formation of the paired internal cerebral veins which replace the primitive diencephalic veins and the PV and annex also the venous drainage of the choroid plexus acquiring progressively the typical horizontal sinuous course. In the meantime many tributaries of the internal cerebral vein develop forming the subependymal and deep medullary veins. The drainage of these veins is centripetally directed. Differently, the flow of the superficial medullary veins is centrifugally directed toward the superficial system. The development of the internal cerebral veins leads progressively to regression of the PV with exception of its more distal part which together with the distal segments of the internal cerebral veins forms the Galen vein draining in the straight sinus. The straight sinus is displaced posteriorly acquiring in the newborn its oblique caudally directed pattern. In addition to the straight sinus, another primitive dural channel can be present called the falcine sinus. It normally disappears. It can, however, be incidentally discovered during normal examinations (Sect. 9.3.3). It is frequently the main venous drainage of Galen vein malformation (Sect. 12.8) often associated with hypoplasia aplasia of the straight sinus. As far as the basal vein is concerned
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