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

SUMMARY: 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.