The orbitotemporal venous sinuses accompany the intracranial branches of the stapedial artery. These sinuses are large in primitive primates and drain the extensive territories supplied by the stapedial artery as well as the brain. The orbit is drained by a wide cranio-orbital sinus which empties into the postglenoid emissary vein. Also emptying into the postglenoid vein is the petrosquamous sinus. The latter diverts cerebral blood from the transverse sinus and also drains the temporalis muscle. Emptying into both the cranio-orbital and petrosquamous sinuses are meningeal tributaries, which drain the cranial side wall and the dura mater. The relatively small sinus communicans runs in the angle between the petrosal bone and the cranial side wall. It commences at the postglenoid vein and connects the distal end of the petrosquamous sinus to the pterygoid venous plexus. In humans, the orbitotemporal sinus system is greatly modified. Its remnants persist for the most part as "middle meningeal veins." The system no longer drains the orbit, the temporal fossa, or the brain. The petrosquamous sinus becomes attenuated or obliterated along part or all of its length. The postglenoid vein vanishes. The cranio-orbital sinus is reduced in diameter and its connection to the orbit is feeble or absent. During development, the posterior end of the cranio-orbital sinus migrates inferiorly along the sinus communicans. In most individuals, this migration ceases at the foramen spinosum, site of the emissary vein of the sinus communicans. Meningeal tributaries are relatively large in humans, and drain principally into the cranio-orbital sinus or sphenoparietal sinus. The sphenoparietal sinus is an evolutionary novelty restricted to hominoids and is frequently developed in only Homo and Pongo.

Data drawn from the perspectives of paleontology, comparative anatomy, embryology, teratology, and normal adult variation were analyzed with nine homology criteria in order to determine the homologues of the stapedial artery in adult humans. It was determined that 1) the stem of the stapedial artery does not persist within the cranial cavity; 2) the stem of the ramus inferior is retained in its entirety and forms the upper portion of the stem of the middle meningeal artery; 3) the proximal part of the ramus infraorbitalis is normally absent and is replaced by a collateral shunt arising from the ramus mandibularis; 4) the ramus mandibularis is retained and forms the lower portion of the middle meningeal stem and the inferior alveolar artery; 5) the most proximal portion of the maxillary artery is formed by an anastomotic shunt connecting the external carotid artery to the ramus mandibularis; 6) the anterior division of the ramus superior is normally present and well developed; 7) the posterior division of the ramus superior is present in many individuals; and 8) the junction of the two divisions of the ramus superior with the ramus inferior usually migrates to the floor of the middle cranial fossa. The range of human arterial patterns, and those of all other euprimates, can be derived from a hypothetical primitive pattern that is very similar to that of primitive rodents. In this pattern, the stapedial artery stem enters the middle cranial fossa and trifurcates into the anterior and posterior divisions of the ramus superior and the ramus inferior. In their evolution, strepsirhines initially lose the ramus inferior and haplorhines initially reduce the stapedial artery stem.

A complete dissection of a persistent stapedial artery and its companion venous sinuses revealed several noteworthy features. The proximal portion of the stapedial artery stem was missing, and the entire stapedial system was supplied through an anastomosis between the occipital artery and the ramus posterior of the stapedial artery; a similar type of collateral supply occurs in some xenarthrans and bats. The ramus posterior is a component of the primitive eutherian stapedial system and one that has not been reported previously in a primate. Both the anterior and posterior divisions of the ramus superior were present. The posterior division is identified here for the first time in a primate. The anterior and posterior divisions were accompanied by the cranio-orbital and petrosquamous sinuses, respectively. These sinuses were incomplete and attenuated relative to the primitive eutherian condition.

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In primitive eutherians, the stapedial artery is the primary supplier of blood to the nonneural tissues of the head. Beyond a certain body size, the stapedial artery can no longer function as the sole supplier to its original territory because the diameter of its stem is limited by the size of the intercrural foramen of the stapes, which exhibits strong negative allometry. Some eutherians have extended the upper limit that the diameter of the stapedial stem can attain by developing a coarctation (narrowing) at the transcrual portion of the vessel. In the Norway rat (Rattus norvegicus) and the golden hamster (Mesocricetus auratus) the coarctation develops in postnatal life and is evidently caused by a retardation in growth that keeps the diameter of the vessel at infantile dimensions. In the rat, additional reduction in the external diameter is produced by a thinning of the tunica media of the arterial wall. A comfortable gap between the wall of the artery and the sides of the intercrural foramen is maintained that most likely facilitates the attenuation of potentially disruptive low-frequency vibrations produced by the arterial pressure pulse. The only negative side effect of a coarctation in rat-sized animals is that resistance to flow is increased and volume flow rate is concomitantly diminished. The coarctation does not create flow disturbances downstream of the constriction. One possible additional benefit of the coarctation is a flattening out of the arterial pressure pulse. It is speculated that the capacity to develop a coarctation once a certain body size is reached is an ancient trait that dates at least as far back as the Early Cretaceous.