Patterns of cranial venous system from the comparative anatomy in vertebrates. Part I, introduction and the dorsal venous system

Abstract

Many classifications of the cerebral venous system are found in the literature but they are seldom based on phylogenic study. Among vertebrates, venous drainage of the brain vesicles differs depending on the species. Due to the variability, poorly descriptive articles, and many different names used for the veins, the comparative study of the cranial venous system can hardly be performed in detail. The cranial venous system in vertebrates can be divided into three systems based on the evolution of the meninges and structures of the brain vesicles: the dorsal, lateral-ventral and ventricular systems. This study proposes a new classification of the venous drainage of brain vesicles using knowledge from a comparative study of vertebrates and focusing on the dorsal venous system. We found that the venous drainage of the neopallium and neocerebellum is involved with this system which may be a recent acquisition of cranial venous evolution.

Figure 1

The evolution of the pallia of the brain. A; Hagfish, B; Urodele, C; Turtle, D; Bird, E; Opossum, F; Human (After Elizabeth C.Crosby with modification) yellow; Archipallium, blue; Paleopallium, dark brown; Neopallium, light brown; Striatum.

Figure 2

Illustration shows similar development of the primary head vein in fish, reptile, bird, rat, calf and man, respectively. A) A 28 hour-old zebrafish embryo. B) A late embryo of Tropidonotus natrix. C) A herring gull embryo after 5-6 days of incubation. D) A rat embryo on day E12-17. E) A 5 week-old calf. F) A 5 mm long human embryo. (Modified from ^-).

Figure 3

Dorsal located veins or sinuses in different adult vertebrates. Even though the mid-dorsal located vein or sinus seems to be similar among vertebrates, the evolution and function are different depending on the species. A) Hagfish. B) Amblytoma tigerinum. C) Testudo geometrica. D) Light Sussex bird. E) Guinea pig. F) Dog. (Modified from^-).

Figure 4

Some of the dorsal venous dispositions in adult man are shown. The occipital sinus can be separated (A) or single (B). The occipital-marginal system can persist as an alternative venous pathway as in hominids (C, right side). The transverse sinus is usually dominant on the right side, which receives venous blood from the superior sagittal sinus whereas the left one is usually small and collects blood from the straight sinus as described ontogenetically by Padget[10] (D), or even missing (E).The SSS can be off-midline but respecting the falx cerebri (E and F are from the same patient). When the epidural veins do not connect with the pial veins, the SSS can be missing leaving a long pial vein runing parallel before emptying into it (D, arrows).