A comparative‐anatomical study of the craniocervical venous systems in mammals, with special reference to the dog: Relationship of anatomy to measurements of cerebral blood flow

Abstract Pathways of the venous drainage from brain have been studied in various mammals to locate sites for cerebral venous blood sampling with least potential admixture of blood of extracerebral origin. Man, rhesus monkey, pig and cat have internal jugular veins leaving the intracranial cavity through the jugular foramina (foramen lacerum). The bulb of the internal jugular vein may be used for withdrawal of cerebral venous blood in this group of species possessing the embryonal type of cerebral venous system. Dog, horse, rabbit, sheep and ox have (superior) dorsal cerebral veins leaving the intracranial cavity through the temporal foramina as the major cerebral venous outflow. The internal jugular vein in this group arises from the pharyngeal, thyroid and esophageal veins and has infrequent and very small or no drainage of cerebral blood from cerebral venous sinuses. On a dog and even more on other mammals of this group in horizontal and supine position, cerebral venous blood rarely can be obtained without significant contamination with extracerebral blood if the sampling takes place centrally from the temporal foramen. On a prone positioned dog the posterior third of the (superior) dorsal longitudinal sinus is the site to obtain cerebral venous blood specimens with minimal admixture of extracerebral blood.