Ophthalmic Origin of the Middle Meningeal Artery

During the course of a carotid arteriographic study an anatomical variation of embryologic and phylogenetic significance was noted (Fig. 1). Subsequently, two other cases were seen (Figs. 2 and 3). Abnormal origin of the middle meningeal artery from the ophthalmic artery instead of from the maxillary artery was reported by Zuckerkandl (1876) and mentioned by Quain (1892) and Whitnall (1932). This abnormality has never previously been demonstrated on arteriography, and because of its significance with respect to development of the cranial arteries, to development of cerebral collateral circulation, and to improper identification with tumor collateral circulation, these cases are presented. Embryology The stapedial artery which forms an anastomosis with the ventral pharyngeal arteries has two primary divisions; the dorsal one to the supraorbital region in company with the ophthalmic branch of the fifth nerve, and the ventral one giving off two branches in association with the maxillary and mandibular roots of this nerve (Fig. 4). The ophthalmic artery anastomoses with the supraorbital division of the stapedial and annexes the distal end of this artery to form its lacrimal branch. The external carotid artery, through its internal maxillary branch, annexes the maxillo-mandibular division of the stapedial artery to form the first part of the middle meningeal artery. The second part of the middle meningeal represents the proximal part of the supraorbital division of the stapedial artery. The most prominent branches of the adult ophthalmic artery are derivatives of the supraorbital division of the stapedial artery. The orbital segment of the original supraorbital division, now part of the middle meningeal artery, becomes the stem of the lacrimal branch of the ophthalmic artery. The embryonic connection between the ophthalmic and stapedial arteries is frequently represented in the adult by a branch connecting the ophthalmic (usually its lacrimal branch) and middle meningeal arteries at the lateral end of the sphenoid fissure or by means of a foramen in the greater wing of the sphenoid. Anomalies of Ophthalmic Artery (2–4) In Hayreh's intensive study of 170 specimens, the ophthalmic artery in 164 cases arose from the internal carotid artery. In 4 cases the artery arose from the internal carotid but the main contribution was from the middle meningeal artery through enlargement of normal anastomoses between the orbital branch of the middle meningeal and the recurrent meningeal branch of the lacrimal artery. In 2 cases the middle meningeal was the only source of the ophthalmic artery. Abnormal origins depend upon the anastomoses established by the ophthalmic artery with adjacent vessels.