Since we started to work in the lateral sellar region (in 1973), a large volume of angiographic material has provided us with exceptional variations that added to the anatomic facts obtained from our dissections. At present, these anatomic facts remain, but the way we look at them and the way we use them for endovascular treatments, has created a need for a different type of approach and understanding. In this report, we present a flexible anatomical view of the intracavernous branches of the internal carotid artery and a scheme to understand and predict the anatomical variations of these collaterals. Four embryonic vessels play an important role in the variations of the arterial supply to the lateral cavernous region: the dorsal ophthalmic artery, the stapedial artery, the trigeminal artery and the primitive maxillary artery. In general each of them partially regresses leaving behind a remnant. However there is a spectrum from their persistence to incomplete regression, resulting in variations of the supply to their distal territories. The term "meningohypophyseal" should be abandoned because it is misleading and improperly used. Complete agenesis is known for a long time; in case of segmental agenesis of the ICA each of the embryonic vessels presented above may represent an alternate route to bypass the agenesis. The ICA is not a direct feeding artery but a succession of independant segments which can be the site of various anomalies. An embryonic transdural circle can be individualized; it is constituted by the trigeminal arteries posteriorly, the ICA siphon anteriorly, the transsellar anastomosis and internal maxillary artery connections. Although regressions usually occur in this embryonic transdural circle, its derivatives congenital and acquired arterial pathologies. It also constitutes the key system in determining the arterial variations of the perisellar region.