[Participation of the external carotid artery in orbital vascularization].

The authors present the result of 70 dissections of the arterial vascular system of the orbit. The craniofacial junction is an important location because of possible anastomosis between the two carotid systems. These anastomosis can be situated at the meningeal level, palpebral and also inside the orbit cavity. The embryology of the encephalic vascular supply allows one to explain the possible dual origin of the orbital blood supply. This work shows the frequent participation of the external carotid artery to the orbital vascularisation by mean of three collateral branches: the infraorbital artery, a branch of the maxillary artery, partakes in the arterial supply of the inferior oblique muscle in 85,7% of cases. Usually, the inferior muscular artery which is a branch of the ophthalmic artery also partakes in this supply. In very exceptional cases (2 of 70) the infraorbital artery alone supplies the muscle. the lacrimal artery which can come from the external carotid system either from the middle meningeal artery or from the anterior deep temporal artery. This meningolacrimal artery can be either a solo lacrimal artery (17,14% of cases) or be associated with another classical lacrimal artery, from the ophthalmic artery (11,43%). These lacrimal arteries coming from the external carotid system have the following characteristics: they are thinner than classical arteries, they penetrate the orbit by their own orifice, the Hyrtl canal, and they can participate in the muscular vascularisation, especially of the lateral rectus. When these arteries are unique, most often they are encountered when the ophthalmic artery has undercrossed the optic nerve.(ABSTRACT TRUNCATED AT 250 WORDS)